STATEMENT OF FINDINGS CHATFIELD LAKE, COLORADO
1. I have reviewed and evaluated, in light of the overall public interest, the relative information concerning the actions remaining on the authorized project, as veil as the stated views of other interested agencies and the concerned public relative to these remaining actions and their effect along the South Platte River including the Denver metropolitan area. My review also considered all of the impacts discussed in the Final Environmental State ment, some of which are specifically referenced in succeeding paragraphs. A supplemental environmental statement will be pre pared for the downstream channel portion of the project extending from Chatfield Lake to Denver when a plan of flood protection is recommended for that reach of the South Platte River. At the time of submission of the final supplemental environmental state ment, a supplemental Statement of Findings will also be prepared.
2. The possible consequences of the various alternatives have been studied according to environmental, social well-being, and economic effects, including regional and national development and engineering feasibility. The various elements considered include those identified in Section 122 of Public Law 91-611 and the Conference Report on H.R. 9270, 92d Congress.
3. In evaluating the alternatives, the following points were con sidered pertinent:
a. Authorization and current project status.
(1) The Flood Control Act of 1950 authorized construction of Chatfield Dam and Lake and channel improvements along portions of the South Platte River from the dam downstream to Fort Morgan. The Chatfield portion of the project was funded for construction following the flood of record which occurred in June 1965.
(2) Chatfield Dam is located on the South Platte River immediately downstream from the Plum Creek confluence in Jefferson and Douglas Counties, Colorado. It is a rolled earthfill structure which has a crest length of 13,057 feet at elevation 5527.0 feet above mean sea level. The multipurpose pool of the lake will have a normal surface area of 1,150 acres at elevation 5**26 feet above mean sea level.
(3) Project construction is nearing completion; the embankment is scheduled for completion by July 1975. Interior roads, utilities, and recreation facilities are under construction and are scheduled to be completed during 1977. (U) I find that completion of the project as presently- authorized will reduce flooding in, and provide recreation for, the Denver metropolitan area. Benefit-cost studies show that benefits to be derived from completion of the authorized project will exceed the cost of the project (Final Environmental State ment , page 9) •
(5) I recognize, as described in the Final Environmental Statement, page 53, that completion of the project will cause inundation of 13 miles of stream with conseauent fish and wildlife habitat losses. I also recognize that completion of the project will cause evaporation of approximately 2,500 acre-feet of water yearly and, during construction, create minor additional air pollution and consume some fuel.
b. Alternatives which are still viable.
(1) I considered the alternative of not completing con struction of the project. Since construction of the major project features is essentially complete, this alternative would affect only the completion of access roads, interior roads, recreation facilities, and utilities. I recognize that providing access without providing interior roads and utilities to control use would result in environmental damage. Some disruption of public services would also result from this alternative because some utility relocations are still under construction. Under this alternative, the Corps would not fulfill its obligation to provide recreation, one of the authorized purposes of the project.
(2) I considered operation of the completed project as a dry dan. Under this alternative, there would be no loss of flood control, the main project purpose. There would be no initial development of a lake fishery, although this option would remain open for the future. The recreation benefits from this alternative would be only a fraction of the benefits to be realized with the recommended project. Some temporary mudflats could develop fol lowing flooding conditions.
(3) I considered operation of the completed project for flood control and water supply only. Under this alternative, most of the recreation benefits of the authorized project would not be realized. This is because most of the planned recreation at the Chatfield Lake project is water oriented. The benefits to be derived from fishing would also be small because of restrictions normally placed upon use of municipal water supply storage. Mud flats could develop because of fluctuating water levels associated with water supply requirements. c. Other alternatives not currently tinder consideration. Because a major portion of the project has been completed, the following alternatives are no longer considered viable. I list them in order to show what alternatives were evaluated early in the planning of this project.
(1) I considered alternate damsites both upstream and downstream from the recommended site and various combinations of sites.
(2) I also considered downstream channel modifications as a solution to Denver's flood problems.
(3) I considered evacuation of the flood plain as an alternative solution to Denver's flood problems.
(U) I considered the alternative of flood proofing structures and bridges in the flood plain.
U. After weighing the data contained in the Final Environmental Statement, I find that not all adverse effects can be avoided; however, the benefits attributed to the project are much greater than the adverse effects. I find further that the decision to com plete the project as authorized is based on a thorough analysis and evaluation of the.alternative courses of action and is the most feasible and desirable method of achieving the required flood control and the recreation.
5. I recommend that the Corps of Engineers proceed with the neces sary action to complete the Chatfield Lake, Colorado project as authorized.
1 0 FEB 1375 Date JguSsELL A. GLEN~ Colonel, Corps of Engineers District Engineer
.1 concur with the_Findings of the^fitaEhlct Engineer.
Date PHILIP VT. BOERGER DATE j j L W. MORRIS ^ a j o r General, USA Director of Civil Works FINAL ENVIRONMENTAL STATEMENT CHATFIELD LAKE, COLORADO Prepared t>y U.S. ARMY ENGINEER DISTRICT, OMAHA, NEBRASKA January 1975 SUMMARY * CHATFIELD LAKE, COLORADO ( ) Draft (X) Final Environmental Statement Responsible Office: U.S. Army Engineer District, Omaha, Nebraska 1. Name of action. (X) Administrative ( ) Legislative 2. Description of action. A dam and lake is being constructed just downstream from the confluence of the South Platte River and Plum Creek. The dam is a rolled earthfill structure, over 13,000 feet long, and the project purposes are flood control and recreation. The lake will have a permanent multipurpose pool of 1,150 acres; total lands will be 6,919 acres. Recreational opportunities and facilities would be provided at the lake project. 3. a. Environmental impacts. The Chatfield project would pro vide flood control, increase recreational opportunities, maintain open space, lead to changes in water quality, lead to changes in populations of fish and wildlife, change rates and overall amounts of sand and gravel extraction within project boundaries, provide scientific and educational opportunities, disrupt some existing scenic resources, cause a loss of agricultural produc tion, result in a loss of tax base which would probably be temporary, cause a small loss of hunting opportunity, and result in water evaporation losses. b. Adverse environmental^Impacts. Some loss of stream fish habitat and riparian vegetation, loss of agricultural pro duction, loss of hunting opportunity, water evaporation losses, disruption of existing scenic resources, and a temporary loss of tax base would occur. H. Alternatives. The alternatives open for present considera tion are to operate the nearly completed project as a dry dam, operate the project for flood control and water supply, and do not finish construction, either leaving construction in its present stage of completion or removing present construction and attempting to return the area to preproject conditions. During studies prior to authorization of the Chatfield project, many alternative solutions to alleviate flood problems on the South Platte River and Plum Creek were considered. These include alternate damcites both upstream and downstream from the Chatfield site, downstream channel modifications, evacuation of the flood plain downstream from the Chatfield site, and flood proofing of structures and bridges in the flood plain downstream from the Chatfield site. For various reasons none of these latter alternatives are currently viable. 5. Comments received. Denver Regional Council of Governments Colorado Department of Highways Town of Columbine Valley State of Colorado, Division of Wildlife Soil Conservation Service, U.S.D.A. Federal Highway Administration, U.S. Dept, of Transportation State of Colorado, Division of Water Resources Colorado Water Conservation Board U.S. Department of the Interior, Missouri Basin Region Department of Housing and Urban Development State of Colorado, Division of Planning Forest Service, U.S.D.A. Department of Planning, City and County of Denver U.S. Environmental Protection Agency The Wilderness Society Metro Denver League of Women Voters Hugh Kingery, Denver Field Ornithologists Dam the Platte Committee 6. Draft Statement to CEQ 6 May 197^. Final Statement to CEQ ^ ^ lerrifr. CHATFIELD LAKE, COLORADO TABLE OF CONTENTS Summary Statement Page I. PROJECT DESCRIPTION INTRODUCTION 1 AUTHORIZATION 1 PROJECT HISTORY 1 RELATIONSHIP OF CHATFIELD LAKE TO BUREAU OF RECLAMATION'S TOO FORKS RESERVOIR 3 XMBANKMENT h OUTLET WORKS . h SPILLWAY 5 ROADS AND UTILITIES 5 PERMANENT POOL 5 PROJECT OPERATIONS 6 LOCAL COOPERATION 6 PLAN OF DEVELOPMENT 7 VEGETATIVE MANAGEMENT 7 GRAVEL EXTRACTION 8 PROJECT ECONOMICS 8 II. ENVIRONMENTAL SETTING WITHOUT THE PROJECT BASIN DESCRIPTION 10 Location 10 Physiography 10 Topography Geology 10 Summary Statement ^aSe EXISTING WATER RESOURCE PROJECTS IN THE BASH 11 Cherry Creek Dam and Reservoir H Aurora Detention Dam 11 Watershed improvements H Local protection H Two Forks 12 Bear Creek Lake 12 PROJECT AREA DESCRIPTION 12 General 12 Stream characteristics 12 Physiography 13 Topography 13 Geology 13 Flora 1^ Fauna 15 necreanion use 15 Gravel resources 20 Economic-social 20 Archeoiogical/historical/cultural 21 Scenery 22 Land use and population growth 22 WATER QUALITY 22 Temperature 23 Turbidity 23 Flows 23 pH 25 Ammonia (NH_) 25 Nitrate (NO;?) 25 Phosphates vPO^) 26 Dissolved oxygen 26 Algae 26 Bacteria 26 III. RELATIONSHIP OF THE PROPOSED ACTION TO LAND USE PLANS POTENTIAL IMPACT AREA 28 POPULATION GROWTH AND LAND USE 28 AUTHORITY TO CONTROL GROWTH 31 Summary Statement Page IV. THE ENVIRONMENTAL IMPACT OF THE PROPOSED PROJECT ENVIRONMENTAL IMPACTS 38 BENEFICIAL IMPACTS DISCUSSED 38 Flood control 38 Recreation and scenic attractions 39 Open space 1*0 Changes in water quality 1*0 Fish and wildlife habitat 1*1 Gravel resources 1*1 Educational opportunities 1*1 DETRIMENTAL IMPACTS DISCUSSED 1*2 Loss of vegetation 1*2 Recreation 1*2 * T_ J- - — ... . > * i . . )t O I I U W W A 4. W J Fish and wildlife 1*3 Gravel resources 1*1* Secondary scenic impact 1*1* Loss of agricultural production 1*1* Loss of hunting opportunity 1*5 Potential tax loss 1*5 Effect on urbanization 1*5 Effect on archeological resources 1*6 REMEDIAL, PROTECTIVE, AND MITIGATIVE MEASURES 1*6 Loss of vegetation 1*6 Water quality 1*9 Storm severs 1*9 Pollution abatement 1*9 Fish and wildlife 50 GRAVEL 51 Existing resources 51 Extraction operations 51 Scenic 52 Preservation of open space 52 Mining Operations 52 Archeological resources 52 Summary Statement Page V. ADVERSE ENVIRONMENTAL EFFECTS WHICH CANNOT BE ' AVOIDED SHOULD THE PROJECT BE IMPLEMENTED VI. ALTERNATIVES TO THE PROPOSED ACTION ALTERNATIVES 51* Operate as a dry dam 5** Operate the project for flood control and water supply 55 Do not finish construction 5b Other alternatives not currently under consideration 57 Alternate damsites Both upstream and downstream from the Chatfield site 57 Downstream channel modifications 57 Evacuation of the flood plain downstream from the Chatfield site 57 Flood proofing of structures and "bridges in the flood plain downstream from Chatfield 57 Roi’+h Fi.v**'** #»ifl to P^nvoT 58 VII. LOCAL SHORT-TERM USES OF MAN'S ENVIRONMENT VERSUS THE MAINTENANCE AND ENHANCEMENT OF LONG-TERM PRODUCTIVITY VIII. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENTS OF RESOURCES WHICH WOULD BE INVOLVED IN THE PROPOSED ACTION SHOULD IT BE IMPLEMENTED IX. COORDINATION WITH OTHERS PUBLIC PARTICIPATION 63 GOVERNMENT AGENCIES 6? Denver Regional Council of Governments 65 Colorado Department of Highways 65 Town of Columbine Valley, Colorado 67 Divi'-ion of Wildlife, State of Colorado 67 U.S. Department of Agriculture, Soil Conservation Service 67 Department of Transportation, Federal Highway Administration 67 PLATES Plate No. 1 Basin map 2 Project access and off-project signs 3 Land and water use map 1+ Downstream channel improvements 5 Gravel extraction master plan APPENDIXES Appendix No. I A record of field observations of the birdlife of the South Platte River, in the vicinity of Vaterton, Jefferson, and Douglas Counties, Co3 evado II Archeological survey of the Chatfield Reservoir, Colorado, 1968 III Letters received from governmental agencies, . citizen groups and individuals commenting on the draft environmental statement Summary Statement Page Colorado Division of Water Resources 69 Colorado Water Conservation Board 69 U.S. Department of the Interior, Missouri Basin Region TO Department of Housing and Urban Development 76 Colorado Division of Planning 76 U.S. Forest Service 79 Department of Planning, City and County of Denver 81 U.S. Environmental Protection Agency 82 CITIZEN GROUPS 83 The Wilderness Society 8U Metro Denver League of Women Voters 85 Hugh Kingery, Denver Field Ornithologists 87 Dam the Platte Committee 88 TABLES Table Ho. Page 1 Summary of benefits and costs, Chatfield Lake, Colorado 9 2 Inventory list of flora on three Chatfield areas 16 3 Summary of State water quality standards 2h FIGURES Figure No. Page 1 Potential impact area 29 2 Land use suitability map 30 3 Existing natural gas and electric lines 32 U Water and sewer service boundary 33 . 5 Transportation plan 3I* 6 Employment center and proposed regional transit system 35 1.06 At a meeting on 26 October 1970» officials from the city of Littleton proposed an alternate solution to the flood problem for a portion of the project. The city's solution involved approximately the upstream 2.3 miles of the proposed 7..5-mile project. The Littleton Plan was to bring under public ownership lands subject to flooding if the channel capacity is not improved. These lands vould be utilized as a public open space park with a minimum of development. Littleton, officials recognized tha.t purchn.se of flood plain lands would be beyond their financial capability. They approached the Corps' representatives with the concept that there would be Federal cost savings if the channel work were to be deleted within the upstream segment. They requested that funds saved be made available for the purchase of pari: lands. The existing authorization did not permit such a transfer of funds, and this prompted current legislation. The current legislation, which is a part of the hater Resources Development Act of 197^, reads as follows: r(a) The project for flood control below Chatfield Dam on the Couth Platte River, Colorado, authorized by the Flood Control Act of 1950 (6H Ctat. 175) 5 is hereby modified to authorize the Fecrctary of the Army, acting through the Chief of Engineers, to participate with non- Federal interests in the acquisition of lands and inter ests therein and in the development of recreational facilities immediately downstream of the Chatfield Dam, in lieu of a portion of the authorized channel improve ment for the purpose of flood control and recreation. ”(b) Such participation shall (l) consist of the amount of savings realized by the United States, as determined by the Secretary of the Army, acting through the Chief of Engineers, in not constructing that portion of the authorized channel improvement below the dam, together with such share of any land acquisition and recreation development costs, over and above that amount that the Secretary of the Army determines is comparable to the share available under similar Federal programs pro viding financial assistance for recreation and open spaces, (2) in the instance of the aforementioned land acquisition, be restricted to those lands deemed neces sary by the Secretary of the Army for flood control pur poses, and (3) not otherwise reduce the local coopera tion required under the project. I. PROJECT DESCRIPTION INTRODUCTION 1.01 This environmental statement will describe the remaining construction of the Chatfield Lake project and the impacts of this remaining construction and of the operation and maintenance of the project on the environment. It will also list and evaluate the alternatives remaining open for consideration at this point in time. 1.02 A supplemental environmental statement will address a plan of flood control for the South Platte River between Chatfield Dam and West Hampden Avenue, impacts of the plan, and the various alternatives considered during the planning process. AUTHORIZATION 1.03 Chatfield Dam and Lake and downstream channel improvements were authorized by the Flood Control Act of 1950, substantially in accordance with the recommendation of the Chief of Engineers in House Document No. 669, 80th Congress, 2nd Session. The authorized purposes of the project are flood control and recrea tion. PROJECT HISTORY 1.0U The Flood Control Act of 1950 authorized construction of Chatfield Dam and flood protection along portions of the South Platte River from the dam downstream to Fort Morgan. The Chatfield Lake project was funded for construction following the historic flood of record which occurred in June 1965. The Omaha District recommended and received approval to construct that portion of the authorized project between Chatfield Dam and Denver as a part of the Chatfield project. The State of Colorado provided assurances of local cooperation required by the authorizing legislation for that portion of the project downstream from the dam. 1.05 The proposed downstream portion of the project would provide flood and erosion protection between the Federal acquisition line for Chatfield Dam and the south edge of Denver (Hampden Avenue). A plan for channel capacity improvement was approved in May 1968. That plan provided protection for flows having a 1-percent chance of annual.occurrence with a minimum channel sized to carry the maximum operational release from Chatfield Lake. "(c) Prior to the furnishing of the participation authorized hy this Act, non-Federal interests shall enter into a binding written agreement with the Secretary of the Army to prevent any encroachments in needed flood plain detention areas which would reduce their capability for flood detention and recreation." 1.07 The downstream channel project is currently undergoing a reformulation study to develop a plan of flood control that will be generally supported by affected interests. Upon completion of that study, a report and supplemental environmental state ment will be prepared for public review. RELATIONSHIP OF CHATFIELD LAKE TO EUREAU OF RECLAMATION'S TWO FORKS RESERVOIR 1.08 During the planning and construction phases of this project, the question of providing for municipal and industrial water storage was discussed. At the time little or no local support surfaced for this option. The possibility was again discussed prior to closure of the Chatfield embankment. Again no consensus was reached, and the dam is currently being completed without additional provision for municipal and industrial water storage. 1.09 The Chatfield embankment is not of sufficient size to allow for municipal and industrial water storage in addition to the planned recreation and flood control. Recreation and flood con trol are authorized purposes of the project; municipal and industrial water storage is not. If additional storage is desired at Chatfield, simply raising the height of the embank ment would not be sufficient. A totally new structure would have to be designed. Prior to this a reexamination of the foundation materials would have to be done to insure that the strata would support this increased weight. 1.10 The discussion of possible municipal and industrial water storage in or near the Chatfield Lake project inevitably involves the Bureau of Reclamation Two Forks project. This project, as yet unauthorized, is located about 15 miles upstream from Chatfield on the South Platte River. The Two Forks project could provide flood control, recreation, and/or municipal and industrial water storage. If certain decisions were made now or in the future, there could be trade-offs between Chatfield Lake and Two Forks involving one or more of the above-mentioned storage allocations. It is again mentioned that no decisions have been made concerning possible trade-offs between the two projects. It is certain, however, that if a change in storage allocation is made at Chatfield Lake in the future, a revised environmental statement will be required. EIBAIIKHICT 1.11 Chatfield Dam is located on the Couth Platte River imme diately downstream fron the Plum Creek confluence in Jefferson and Douglas Counties, Colorado. It is a rolled eart'nfill structure, which has a crest length of 13,057 feet at elevation 5527.0 feet mean sea level (m.s.l.). Part of the upstream face of the dan is protected by riprap to prevent erosion from wave action. The downstream face and the upper portion of the upstream face will be grassed with adapted native species to prevent erosion from wind and precipitation. 1.12 The upstream slopes of the embankment are 1 on 2.5 fron crest elevation 5527 feet m.s.l. to 5^93 feet n.s.l.; 1 on 5 between elevations 5^93 feet m.s.l. and 5^31 feet n.s.l.; 1 on 15 between elevations 5^31 feet m.s.l. and 5^20 feet n.s.l.; 1 on 3 between elevations 5^20 feet m.s.l. and 5^08 feet m.s.l.; and 1 on 10 fron elevation 5*i03 feet m.s.l. to ground surface. The downstream slopes are 1 on 2.5 from crest elevation 5527 feet n.s.l. to elevation 5^93 feet n.s.l. and 1 on 5 below that elevation, except at both abutments where the slopes are flared to a 1 on 7 below elevation 5**93 feet m.s.l. The crest of the dan is 30 feet wide with a surfaced road at elevation 5527 feet m.s.l., 1^7 feet above the riverbed. 1.13 As of 31 December 197**, the Stage III Earthwork, which includes the main embankment and required borrow operations, was about 99 percent complete. Closure of Chatfield Dam and diversion of the South Platte River flows through the outlet works were accomplished in August 1973. Initially a notch had been left in the embankment to pass flows while the rest of the embankment was being constructed. Since then, work has been concentrated on earthfill operations to bring this section up to the level of the balance of the embankment. The scheduled completion date for the Stage III Earthwork is 31 July 1975. OUTLET WORKS l.lU The outlet wrorks are located near the left abutment of the dam. The intake tower is equipped with slide gates capable of providing fine control regulation. The outlet works include a conduit with twin oblong barrels, each having inside dimensions of 16.25 feet high by 10.5 feet vide and a total length of 1,120 feet. The conduit empties into a stilling basin at the downstream end of the dan. A 6-foot diameter circular pipe was placed inside one of the barrels of the two-barrel conduit to provide a con tinuous discharge for the needs of dovnstrean users. These needs are for the water rights owned by downstream residents and, when water is available, they are filled on a priority basis. Construction of the outlet works is complete. SPILLWAY 1.15 A concrete-lined spillway has been constructed in the left abutment of the dan. . The crest length is 500 feet at elevation 5500.0 feet n.s.l., and the bottom width is 390 feet. As of 31 December 1?7^, the contract was 99.9 percent complete with only minor work remaining. ROADS AIID UTILITIES 1.16 Other construction at the Chatfield project includes project roads, camping pads and loops, parking lots, picnic shelters, swimming beaches, boat harbors, comfort stations, water and sewer lines, hiking, biking, and horse trails; and landforms. The first phase of this construction, which includes installation of major roads and primary water and sever lines, was about 95 percent complete as of 31 December 197^. Phase II is about 90 percent complete, and phase III is about U3 percent complete. The work will be completed in five separate phases before the completed project is turned over to the State of Colorado, the project sponsor, for the recreation operation and maintenance. PERMANENT POOL 1.17 The storage capacity of 20,000 acre-feet at elevation 5^26 feet ra.s.l. is equal to the estimated 100-year sediment accumula tion. Elevation 5^30 feet n.s.l. represents the upper limit of the multipurpose pool which will have an initial capacity of approximately 25,000 acre-feet. The multipurpose pool will nor mally be operated between elevations 5*^26 and 5^30 feet m.s.l. The pool will have a surface area of 1,150 acres at the lower elevation and about 1,300 acres at elevation 5^30.0 feet m.s.l. Maximum, shoreline distance at elevation 5^30.0 feet n.s.l. will be about 7.5 miles; maximum initial depth at this elevation will be about U8 feet. The flood control pool (elevation 5500.0 feet m.s.l.) will cover U ,550 acres and will have a storage capacity of 215,000 acre-feet in addition to the 20,000 acre-feet of the sediment pool. The maximum pool (elevation 5521.6 feet m.s.l.) vill cover 6,120 acres and have a storage capacity of 120,000 acre-feet of surcharge water. Total storage, including surcharge, will be 355,000 acre-feet. Project lands for all purposes vill total 6,919 acres. 1.18 The lake, or multipurxxDse pool, will have a "V" configura tion - its arms lying in the valleys of the South Platte River and one of its tributaries, Plum Creek. The South Platte River arm of the lake will extend about 2 miles upstream from the dam while the shorter Plum Creek arm vill be about 0.5 miles in length. See plates 1, 2, and 3 for the location and details of the lake project. Plate ^ shows a generalized scheme of the downstream channel project area, including its relationship to the lake project. PROJECT OPERATIONS 1.19 The normal operation of Chatfield Lake will be to allow incoming water to pass through the lake, up to a maximum of 5,000 c.f.s. This will be adjusted from time to time to insure a more or less steady flow, and to insure that the rights of downstream water users are not violated. In the event of flooding conditions downstream from the dam, releases will be curtailed until sufficient channel capacity is available to allow releases. Likewise, during flooding conditions upstream from the dam, releases may be curtailed if inflow is too great to allow it all to be released downstream without causing damages. 1.20 A contract exists between the State of Colorado and the Denver Water Board; it provides for the initial filling of the reservoir and also for supplying vater lost to evaporation. Briefly, the Denver Water Board vill be responsible for main taining the multipurpose pool at 20,000 to 2^,000 acre-fceb. At times it may be allowed to fluctuate as low as 18,000 acre-feet. During extended drought periods, the State shall give its consent in writing to some lesser storage for a prescribed period of time. LOCAL COOPERATION 1.21 The Corps of Engineers is developing sufficient recreation facilities, exclusive of local cooperation, to accommodate the anticipated visitation for the first 3 years. Future recreation development is scheduled to be cost-shared between the Government and the local sponsor after the initial 3-year period. The State has agreed to purchase water for initial filling of the lake to the minimum multipurpose elevation of 5^26 feet m.s.l. and to replace annual evaporation losses. PLAN OF DEVELOPMENT 1.22 The entire Chatfield project, with the exception of those areas required for public highways and project operation facilities, has been allocated for recreational use in one of four separate land use categories. These four categories are day use, overnight use, natural or environmental study use, and open space. 1.23 Day use activities include picnicking, swimming, and water skiing and their associated beaches, shoreline fishing, hiking, bicycling, playgrounds, boating, and sightseeing. 1.2U Overnight use areas will be used for trailer and group camping and for tent and walk-in type camping. 1.25 Areas that are ecologically worthy of preservation, enhance ment or interpretation will be used for natural or environmental study. These areas are to remain relatively undisturbed vith only minor development of trails to accommodate public use. 1.26 Open areas are the scenic areas, the areas too rugged for development, and the buffer zones separating public highways from developed recreation areas. Minimum trail development will pro vide for public use in these areas. 1.27 Additional discussion of facilities, including several plates showing their location, may be found in Design Memorandum No. PC-ID, Master Plan for Chatfield Lake, Colorado, dated October 1973. Additional information concerning recrea tion development may also be found in this document. This docu ment may be examined at the office of the District Engineer, Omaha, Nebraska. 1 .28 A.map of the planned land and water uses of Chatfield Lake is shown on plate 3. VEGETATIVE MANAGEMENT 1.29 The U.S. Forest Service and the Colorado State Forest Service have, under contract with the Corps, instituted pro grams to save as many existing trees as possible on the project lands and to plant additional trees for recreation, •wildlife, and scenic "beauty. Only adapted native or timeproved species of grasses and trees are being used in the revegetation of disturbed jjroject areas. GRAVEL EN1TACTICN 1.30 retraction of gravel is currently taking place in the pool area of Chatfield and will continue until impounded water prevents this operation. In the upper end of the Couth Platte a m of the pool area, extraction is restricted seasonally to protect the heron rookery during the breeding and nesting season. Location of gravel extraction areas and typical sections for gravel removal are shovn on plate 5. 1.31 Extraction of considerable amounts of gravel is being planned for the upstream reach of the Couth Platte River a m of the Chatfield project. The extraction will be contracted out to private firms on a competitive basis. The primary purpose of this extraction is to permit removal of a valuable resource. A significant secondary benefit is the creation of numerous ponds to enhance fish and wildlife habitat at the Chatfield project. 1.32 No excavation will be permitted within the river channel, nor will contractors be allowed to disturb critical native habitat adjacent to the project area. Other restrictions placed on potential contractors, plus proposed safety and mitiga tion measuresi are presented in Section IV of this statement. The shaded area on plate 5 along the South Platte Piver above the multipurpose pool is the area where this extraction will occur. PROJECT ECONOMICS 1.33 The total investment for the Chatfield Lake project, based on July 1971* price levels, is currently estimated to be $9^,320,000. This figure includes a Federal cost of $814,300,000, a non-Federal cost of $14,790,090, and interest during construction in the amount of $5,220,000. The annual economic cost of the project, based on the above figures and a 3.25 percent interest rate is $3,692,700. I.3I4 Annual economic benefits for the Chatfield Lake project are $21,1429,600. This includes $19,39^,600 for flood control . and $2,035,000 for recreation. Table 1 presents a comparison of annual costs and benefits. 1.35 The current interest rate, specified by the new Water Resources Council, "Principles and Standards for Planning Water and Related Land Resources", is 5.875 percent. The 3.25 percent interest rate was the rate in effect at the time of project authorization and was, therefore, the rate used for the Chatfield economic calculations. 1.36 The current benefit-cost ratio for this project is 5.8 to 1.0 using the 3.25 percent interest rate. If the 5.075 percent interest rate was used, the benefit-cost ratio would be reduced by perhaps one-third, to about 3.8 to 1.0. TABLR 1 SUMMARY OF BENEFITS AND COSTS" CHATFIELD LAKE, COI/HADO ANNUAL BENEFITS Account Amount Flood Control $19,39^,600 Recreation 2,035,000 Total $21,1*29,600 ANNUAL COSTS Account Amount Interest and Amortization $ 3,089.900 Operation and Maintenance 572,800 Economic Losses 30,000 Total $ 3,6o 2,700 TOTAL COSTS Amount Federal $81* ,300,000 Non-Federal 1 ,890,000 Contributions (Non-Federal) 2,900,000 Total $89,090,000 Interest During Construction 5,230,000 Total Project Investment $9^,320,000 *Based on July 197^ price levels. ii. rnviroitmrntal cutting without tes project basin dpccription 2.01 Location. The South Platte River basin is roughly rec tangular in shape with an elongation at the northeast corner which extends to North Platte, Nebraska. It is bounded by the following river basins, beginning at North Platte, and proceeding clockwise around the basin: the Republican, Arkansas, Colorado, and North Platte Rivers. The total area of the basin is about 2^,000 square niles; 19,000 square niles are in Colorado, 3,000 in Nebraska, and 2,000 in Wyoming. 2.02 The South Platte River originates along the Continental Divide near Fairplny, Colorado. It flows southeast to Pleven Mile Canyon Reservoir, northeast through Denver toward Greeley, Colorado, east to Tort Morgan, Colorado, and then northeast to its confluence with the North Platte River at North Platte. 2.03 Physiography. The South Platte River basin lies in two of the major physiographic divisions of the United States - the Rocky Mountain System and the Interior Plains. About 25 percent of the basin consists primarily of mountain ranges while the remainder is characterized by broadly terraced plains land. 2 .0U Topography. The western boundary of the basin is formed by the Continental Divide, with elevations up to lH,000 feet m.s.l., and the Laramie Range, with elevations up to 10,000 feet n.n.l. At the southwest corner of the basin, the mountain area known as South Park is a nearly flat area at an elevation of about 10,000 feet m.s.l.; it is surrounded by mountain ranges varying in elevations from 12,000 to 1^,000 feet m.s.l. Rlevations in the plains region vary from approximately 7000 feet m.s.l. along the foothills to approximately 2800 feet m.s.l. at the eastern boundary of the basin. 2.05 Geology. A belt of hogbacks marks the western boundary of the plains and divides the South Platte River basin into two geologic regions. The region west of the hogbacks is underlain primarily by rrecambrian igneous and metanorphic rocks, including’granites, schists, and gneisses. The hogbacks are composed of eastward dipping sedimentary rocks consisting of sandstones, shales, and limestones. They range in age from Carboniferous to Tertiary. The region east of the hogbacks is underlain by Tertiary and Quaternary continental deposits com posed of compact sands, silts, and clays. Throughout the lower portion of the "basin, most of the Tertiary deposits have been removed by erosion. The river valley is typically veneered with Recent terrace, as well as flood plain sand and gravel deposits. EXISTING WATER RESOURCE PROJECTS IN THE BASIN 2.06 Cherry Creek Drjn and Reservoir. The Cherry Creek Reservoir project is located on Cherry Creek about 6 niles southeast of Denver. It was authorized by the Flood Control Acts of 19^+1 and 19^^. It controls a drainage area of 366 square niles, or about 8 percent of the total drainage area above Brighton. The reser voir has a gross storage capacity of 229,652 acre-feet, of which 13^,681+ acre-feet are surcharge storage. Of the remaining 95,966 acre-feet of storage, approximately 15,00 acre-feet are devoted to the 870-acre multipurpose pool. By 1970 annual visita tion had risen to nearly 960,000. By the year 2000 annual visita tion is expected to reach 1.6 million. 2.07 Aurora Detention Dan. A small impoundment, capacity 380 acre-feet, was constructed by the Corps of Engineers pursuant to Section 212 of the 1950 Flood Control Act. It is located on a small watercourse (Westerly Creek) near the junction of the southwest city limits of Aurora and the southeast city limits of Denver, at the north end of Lowry Air Force Base. This project, completed in 195^ at a cost of $227,000, provides local flood protection in the immediate Aurora area, but has no effect on South Platte River floods in Denver. 2.08 Watershed irvnrovements. Watershed improvements in the Denver area of the South Platte River basin are limited to the Franktown- Parker and West Cherry Creek projects. These projects, developed by the Soil Conservation Service, are located in the Cherry Creek basin upstream from the Cherry Creek Dan and Reservoir. They have no effect on the South Platte River floods in Denver. 2.09 Local protection. Locally sponsored improvements which have some flood control effectiveness along the South Platte River through Denver are limited to improvements of the main channel". These improvements consist essentially of revetted levees, limited rock-bank protection, timber and concrete retaining walls, and erosion control weirs or drop structures. These improvements have been effective against minor floods, but are not adequate for major floods on the South Platte River. 2.10 Two Forks. The Bureau of Reclamation has done some initial studies on the potential Two Forks Dam and Reservoir. The site for this project is on the South Platte Fiver at the junction of the north fork of the South Platte River and the main stem, approximately 15 miles upstream from the Chatfield site. Addi tional discussion on this project can be found in Section I. 2.11 Bear Creek Lake. The Bear Creek Lake, Colorado project was authorized for construction by the Flood Control Act of 1968. Construction was initiated in the fall of 197**; completion of the outlet works is tentatively scheduled for 1 October 1976 and completion of the embankment is scheduled for 1 October 1979. The project consists of a dam and a 110-acre lake on Eear Creek for the purposes of flood control, general recreation, and fish and wildlife enhancement. Flood control for the Denver metro politan area is partially dependent on the Bear Creek Lake project. The other elements of the flood control system are Chatfield Lake, which is under construction, channel modifications below Chatfield, which is under reformulation, and the Cherry Creek project, which is complete. PROJECT AREA DESCRIPTION 2.12 General. The Chatfield project exerts flood control influence over a portion of the South Platte River basin down stream from the dan. The portion of the basin influenced by the Chatfield project lies generally above Brighton, Colorado, as shown on plate 1. 2!ost of this area is included in the Denver standard Metropolitan statistical /rea (SMSA), which has a population of 1,227,529 (1970 census). The drainage area above Brighton is **,850 square miles; above the Chatfield site the drainage area is 3,018 square miles. Principal tributaries to the South Platte River, all converging on the metropolitan area, include Plum, Bear, Clear, Sand, and Cherry Creeks. Drainage areas of these tributaries are 32*+, 262, 575, 191, and *+09 square miles, respectively. 2.13 Stream, characteristics. The slope of the South Platte River in the plains region averages about 8 feet per mile down stream from Denver. It is about 13 feet per mile between Denver and the foothills of the Rocky Moutains. The stream slope is about 70 feet per mile in Platte Canyon where the South Platte River flows in a narrow gorge through the Front Range. The stream gro.dient varies in the higher mountains from-a'minimum of about 20 feet per mile through the South Park area to more than 1,000 feet per mile near the source. The channel capacities of the South Platte River and its tributaries vary throughout the plains region, the area of prime flood control interest. In general, the channels are inadequate to contain the normal spring rises. The only improved reaches lie within the city of Denver along the South Platte River, Little Dry Creek, and Cherry Creek. Even within the improved reaches, bridges and other channel crossing structures restrict the capacities of the channels. Flooding occurs with discharges as low as 1,500 c.f.s. along some reaches of the South Platte River upstream from Denver. 2.lU Physiography. The Chatfield Lake area lies within the Great Plains physiographic province. Regionally, the area lies along the east flank of the Rocky Mountain Front Range, which consists of Precambrian crystalline rocks. The formations are hogbacks of steeply tilted beds of Paleozoic, Mesozoic, and Cenozoic sedimentary rocks, which are raised up by the uplift of the Front Range. Flat, grass-covered tablelands, called pediments, slope eastward from the hogbacks. These pediments are covered by coarse alluvium and are separated from each other by flat-bottomed valleys. The South Platte River flows north eastward across the area in a broad valley that is bordered by terraces of alluvium. 2.15 Topography.' The South Platte River, in the vicinity of the project, flows on an alluvial plain of sand and gravel approxi mately 3,600 feet wide. The flood plain is flanked on either side by moderate slopes carved from the higher lying alluvial deposits. The average elevation of the flood plain in the area of Chatfield Dam is 5390 feet m.s.l. The left abutment attains elevation 5520 feet m.s.l. about 2,000 feet from the centerline of the river. The right abutment attains the same elevation about 3,200 feet from the centerline of the river. The river flows along the left side of the flood plain at the damsite and angles northeast through a broad flood plain that bisects Metropolitan Denver. 2 . 1 6 Geology. In the vicinity of the damsite the South Platte River flows in a wide valley which parallels the Front Range of the Rocky Mountains to the west. At one time, the river flowed as much as 50 feet lower than its present level; however, a reduction of the gradient of the stream caused marked aggradation. This resulted in alluvial materials being deposited in the valley. These materials consist mainly of sands, gravels, and sandy clays which were derived from the weathering and erosion of the parent materials of the mountains to the west. On the right slope of the valley, the materials consist chiefly of sands and gravels with an occasional layer of silty or clayey sand. The overburden on the right slope is approximately 50 feet in thickness. The embankment and a portion of the reservoir area directly upstream from the embankment are underlain by the Dawson formation. This is succeeded further upstream by formations of Cretaceous age. With the exception of the extreme upstream portion of the reser voir, these formations lie in narrow belts perpendicular to the old channel. All of these formations should form a tight basin. Considerable amounts of sand and gravel overlie the bedrock formations and will "absorb" large quantities of water when the lake is first filled. Once they are saturated, there should be no further effect. The Dawson formation has sufficient strength to support the various types of structures for the project. 2.17 F3ora. The natural (climax) vegetation of this area is the short grass plains; the most important grass species are blue grama (Bouteloua gracilis) and buffalcgrass (Buchloe dactyloides). Other less commonly occurring species are some of the wheatgrasses (Arronyron spp.) and some needlegrasses (Ctlpa srm.). One common weedy invader species is cheatgrass (Broraus tectorun). This is an introduced species which is known to be indicative of severely deteriorated range conditions. 2.18 Trees are uncommon in this physiographic province except along streams. Trees found along streams within the project area include plains cottonwood (Ponuius garmentii), some willows (Salix sr>p.), and an occasional bcxelder (Acer negundo). Other woody species.are very uncommon. 2.19 A grove of large cottonwood trees and associated plants is located along the South Platte River just within the southern limits of the planned multipurpose pool. This grove is the remnant of a much larger grove which extended along the entire stream bottom. All of the trees along the stream within the multi purpose pool area, except for this grove, were cut. This plant association may be properly called a flood plain cottonwood forest. It is one of the more outstanding biological features of the project area. The tract is about 2 k acres in size, with I k acres in mature, dense groves of plains cottonwood inter spersed with 10 acres of open grassland. During the summer of 1 9 1 k , gravel mining operations in the vinicity of this grove apparently led to the mortality of 60 to 70 trees. Death was attributed to a rapid lowering of the water table in the vicinity of the grove. The root system of the trees involved could not recover in time to reach the lowered water table. However, the number of trees lost in 1 9 1 k is insignificant when compared to the rookery as a whole. Positive measures are being taken to insure that future gravel mining operations do not lead to similar problems. A few species of secondary importance are also found within the groves. These are lanceleaf cottonwood (Populus acuminata), boxelder, and some willows. Understory plants are mainly poison hemlock (Conium naculatum), Canadian thistle (Cirsium arvense), slender wheatgrass (Aaropyron trachycaulum), irestern snowberry (Symhoricarpos occidentalis), golden currant (Pibes aurevim), woodbine (Partbenocissur. inserta), and wild grape (vitis riraria). The grassland areas are composed mainly of slender wheatgrass, Canadian thistle, and small amounts of smooth brome (Bromus inermis). 2.20 Other plants found growing in low places adjacent to the grove include shrubby willows (Salix son.), common cattails (?.;-nha 1 a tifo lia ), bulrushes (Scirons spp. ), and some sedges (Caro;: spp. ). 2.21 Table 2 is an inventory lis t of plants found on the Chatfield project. 2.22 Fauna. There.are no known endangered species which would be affected by the project. This is based on consultation with the United States List of Rndangered Species dated ’lay 197*4, published by the U.S. Department of the Interior. 2.23 Fish habitat of the South Platte Fiver and its tributaries within the Chatfield Lake site is poor to fair. The South Platte Piiver within the Chatfield project area supports a variety of fish. Rainbow and brown trout, in sizes from *4 inches to 19 inches, are occasionally found in the area and in the basin upstream from the project area, where they reproduce. Another cold-water species found in the area is the western white sucker. Uarn-water species include numerous yellow perch, a few carp, and occasionally, largenouth bass and sunfish. 2.2*4 Although the South Platte River is subject to severe dewatering by irrigation diversions, trout production is good in the extreme upper reach<.during wet years. The remainder of the South Platte River, which includes the project area, takes on characteristics sim ilar to those streams of the plains area. Pools are scarce and the shifting channel bed results in temporary pools which greatly lim it bottom-food production. 2.25 Plum Creek is a principal tributary of the South Platte River within the Chatfield project area. The creek does not TABLE 2 INVENTORY LIST OF FLORA ON THREE CHATFIELD AREAS** Ab Abundant C o C o m o n Oc Occasional M l a r i • A b s e n t * - M w I O a 8 a 1 1 o sc 3 FAMILY ( F u l l y nan.t) « St to H g FAMILY (Family name) M H « g Genua avedea Corn-ion n a m e UJ ki a p tc Oenun ereci*a Coiraen name n H_ a ACLH*w.EAb (Maple family) CCMc CSiTAE (cone.) Acer negieido B o x e l d e r Ra R a • Lactuca pulchalla Ra Ra R a (Amaranth faall y ) AMAttA.'iiHAltAi Lac Luca acaricta Prickly lettuce O c R a R a Amorantnua retrofiesus Redroot plgveed O c O c Oc liatrus punctata Dotted gayfeather Co _ R a a USMATIV l AE (Water Plantain faally) lygodsamia funcea Skeletonweed Rs . Ra •Sellout w t d i — i« diflnid by the Colorado Furo Slid Low **The inventory was conducted by David L. Putnam and Frank A. Keppclman, graduate students in botany and horticulture at • Colorado State University. support a significant fishery; it is limited almost exclusively to minnows. Deer Creek is the other prinicpal tributary of the South Platte River within the Chatfield project area. It pro vides modest trout habitat during wet cycles. 2.26 Wildlife habitat consists of growths of large cottonwoods along the South Platte River and an understory of willows, wild roses, and forbs. Plum Creek is bordered by large cottonwoods with little understory, due to grazing and the scour effect of floodwaters. Deer Creek, Massey. Draw, and other tributaries which join the South Platte River within the project area sup port good habitat for mule deer and upland game. Heavy growths of willows, alders, and forbs occur along these streams. Wildife travel lanes and escape cover exist along the fence rows and irri gation ditches of the cultivated fields. 2.27 Mammals observed in the project area include red fox, raccoon, skunk, whitetail deer, and beaver; the habitat avail ability, however, has suffered from urbanization. 2.28 Members of the Denver Field Ornithologists have studied the Chatfield project area for the past several years. Members have compiled a list of birds seen in the Chatfield area. The pre viously described grove of cottonwoods within the Chatfield multi purpose pool boundary has received extensive coverage. This grove is the site of a great blue heron rookery. 2.29 The varied natural habitats of the grove, and other similar habitat upstream, provide nesting sites for the rich birdlife. Herons, owls, and hawks nest in the crowns of the cottonwoods. Yellow warblers, redstarts, vireos, and kingbirds nest high in the canopy of the trees. Orioles, goldfinches, robins, and pewees nest in the middle elevation of the forest. Towhees, chats, MacGillivray's and Virginia's warblers, catbirds, and scrub jays nest in the brushy areas and on the ground. Pheasants and meadowlarks nest in the open grassland areas. Hole-nesting birds include the flickers, downy woodpeckers, chickadees, house wrens, starlings, and screech owls. These birds prefer to nest in dead trees rather than live ones. 2.30 Migrating birds have habitat preferences similar to resi dent birds. Many warblers, tanagers, and finches feed in the upper reaches of the trees. Sparrows, juncos, and thrushes are found in the understory. Ducks, geese, sandpipers, and the . unique dipper are found along the river. 2.31 The following birds, in the classifications of breeding birds, regular visitors, and irregular visitors, have been observed in the flood plain cottonwood forest. Breeding birds, in order of decreasing numbers of nesting pairs observed, are house wen, yellow warbler, western wood pewee, robin, great blue heron, mourning dove, downy woodpecker, red-eyed vireo, bullock's oriole, American redstart, red-shafted flicker, black- capped chickadee, starling, warbling vireo, ycllovthroat, American goldfinch, lesser goldfinch, eastern kingbird, yellow-breasted chat, mallard, red-tailed hawk, great horned owl, broad-tailed hummingbird, rufous-sided towhee, white-breasted nuthatch, and brow-headed cowbird. 2.32 The cottonwood biome supports about 1*0 nesting species of birds. Population densities, calculated from studies, are as high as 68U birds per 100 acres. Ouch densities equal those of the highest populated habitats throughout the country. This is due to the wide variety of habitat available in and around the grove. Regular visitors to the grove, but not nesting there, are the killdeer, common nignthawk, belted kingfisher, barn swallow, black-billed magpie, and lazuli bunting. Irregular visitors are the violet-green swallow, cliff swallow, catbird, Audubon's warbler, ’Wilson's warbler, common grackle, red-winged blackbird, house finch, chipping sparrow, white-crowned sparrow, and song sparrow. These birds have been seen mainly in the flood plain cottonwood grove. Other species of shore birds, songbirds, wading birds, and ducks, have been observed throughout the project area. A report containing the names of 183 species of birds and pertinent data concerning each species is attached as Appendix I. This report entitled "Green Ribbon Birds" was prepared by the Denver Field Ornithologists and it indicated the diversity of birdlife found along the South Platte River in and around the Chatfield project site. 2.33 Recreation use. It is estimated that fishing in the streams within the Chatfield project area would have amounted to about 2OO0nan-days annually without the project. Prior to about 1970, it was estimated that 15 miles of the South Platte River down stream from the dam would support about 500 nan-days of fishing annually, with or without the Chatfield project. A few years ago, however, the Denver City Health Department instituted measures to curb pollution of the South Platte River. These measures have been effective in substantially improving the water quality. This improvement led to a recent series of hearings. These hearings resulted in the upgrading of water quality standards and classification for certain reaches of the river. 2.3^ Occasional use of the valley floor, side slopes, and tributary drains is made by nule deer. However, deer hunting is quite restricted because of urban end industrial development, highways, and railroads within the project area. 2.35 Cottontails, nourning doves, and pheasants are the principal upland game in the project area. 2.36 Uaterfowl hunting is sporadic along the Couth Platte River and adjoining sand and gravel pits. It is estimated that about 300 nan-days of waterfowl hunting occurred annually without the project. 2.37 Although muskrats and a few beavers and mink inhabit the reservoir site, the amount of trapping prior to project con struction was insignificant. 2.30 Gravel resources. There are large quantities of gravel reserves in the Couth Platte River valley in the vicinity of the Chatfield project. These reserves are an important source of gravel for the Denver metropolitan area. 2.39 At the tine construction began on the Chatfield project, Peter Kievit Cons was operating an established gravel removal operation. This particular operation was necessarily terminated at that time. Peter Kiewit Sons, however, was permitted, by reservation in a stipulation for settlement of condemnation pro ceedings, to continue to extract sand and gravel from project lands. 2.^0 The current plan for gravel removal from the Chatfield project area is based on a study by the University of Illinois; the study was sponsored by the national Gand and Gravel Associa tion and was published in 1970. There are currently three con tracts in force for removal of gravel from the multipurpose pool area. IIow that closure has been made, operations will be on a day-to-day basis until the pool fills. Once the pool fills, no further gravel removal.from the pool area will be allowed. 2.Ul Uconomic-social. Prior to the beginning of construction at the Chatfield project area, there were approximately 130 resi dential properties, 29 rural residential homes, 11 farmsteads, a radio transmitting station, a gun club, one commercial building, seven commercial properties, and two gravel operations within project boundaries. There was also a housing development kpovn as Riverside Acres. I'ajor land uses within the project site prior to the beginning of construction were as follows: 1*75 acres of unplotted residential land, 60 acres of unimproved commercial land, 150 acres of unimproved industrial land, 50 acres of unimproved homesites, 270 acres of improved subdivision, commercial sites, improved acreages, 1,310 acres of good gravel deposits, l,0l*0 acres of fair gravel deposits, 90 acres of poor gravel deposits, 21 unimproved residential lots, and 2,795 acres of unimproved rural land (land with subdivision potential, rural farmland, and creek bottoms). 2.1*2 Archeological/historical/cultural. The National Park Service and the Smithsonian Institution have searched the project area for archeological, paleontological, and historical remains. A number of archeological sites had existed on the Chatfield project land, but during the late 1960's, archeologists from the University of Denver surveyed the area and excavated the known sites. No known unexcavated sites remain. A copy of the University of Denver report dated 13 May 1972 is attached as Appendix II. 2.1*3 Two small farmsteads and a one-room schoolhouse are located in a small valley in the Deer Creek arm above the multipurpose pool elevation of the proposed reservoir. These structures date from about 181*9. Use of these structures for project purposes and the addition of other cultural assets of the project are discussed at length in Section IV of this statement. 2.1*1* The Hildebrand Ranch is one of the two farmsteads. It is located in a meadow on the north bank of Deer Creek, midway betweem the Rocky Mountains and Deer Creek's confluence with the South Platte River. This ranch has been nominated to the National Register of Historic Places. The significance of this ranch lies in three areas: (l) its early establishment marks it as one of the first attempts at domestic agriculture in the Rocky Mountain region, coming prior to the advent of the trans continental railroad and at least a full decade ahead of the buffalo slaughter and the subsequent "beef bonanza"; (2) since its establishment, it has been owned and operated by a single family for well over a century, a remarkable occurrence in view of our highly mobile society and propensity for urban migration; and (3) with the exception of occasional improvements, the buildings have survived with remarkable integrity from their 19th-century origins. 2 . 1*5 The 19 February 197** issue of the Federal Register and subsequent monthly supplements have been consulted in the preparation of the final statement. These issues have not revealed any new additions to the list of historic places. 2.1*6 Scenery. The project area is situated just east of the Front Range of the Rocky Mountains with a view of some of the highest peaks of the Rockies in this area. 2.1*7 Land use and population growth. Present land use adjacent to the Chatfield Lake project includes recreational, residential, industrial, and agricultural or open areas. The category of agricultural or open space areas is the largest; about 60 percent of the land still falls in this category. Recreation is the smallest of the uses of lands adjacent to Chatfield. Only a small portion, less than 5 percent, downstream from the dam on the right hank of the South Platte River falls in this category. Industrial areas account for perhaps 20 percent, and residential areas account for over 15 percent of the remaining land adjacent to the project. 2.1*8 An estimated growth plan for the Denver metropolitan area has been plotted. This plan shows significant population den sities extending to the northern boundary of the Chatfield proj ect site by the year 1980. By the year 2000 this expanding population is expected to reach nearly to the southern tip of the Chatfield project, thus surrounding most of the site. WATER QUALITY 2.1*9 The Colorado Water Quality Control Act of 1973 extends the water quality management authority of the State, by providing the enabling legislation to ". . . protect, maintain, and improve the quality thereof for public water supplies, for protection and propagation of wildlife and aquatic life, and for domestic, agricultural, industrial, recreational, and other beneficial uses; ..." It creates the Water Quality Control Commission, basically similar to the Water Pollution Control Commission created by the 1966 Act. It also outlines the duties of the Division of Administration of the State Department of Health . . . which are generally to administer and enforce the provisions of the Act and the water quality control programs adopted by the Commission. 2.50 The 1973 Act changes the number of water quality standards adoped in 1967 from four to two: Class A^, and A„ waters These waters are to be suitable for all purposes, including primary contact recreation. Class B., and B., vaters ------1 -----2 ------Waters of class B^ and B^ are to be suitable for all purposes except primary contact recreation. 2.51 Chatfield lake is located in the South Platte River reach classified B^. The reach extends from the source above Fairplay • to Exposition Avenue in Denver and includes all tributaries and standing bodies of water on the main stem. 2.52 Table 3 presents.the summary of State water quality standards. The standards for lakes and streams differ in the maximum phosphorus level allowed. 2.53 Potential problems in wastewater treatment will arise as the planned industrial area is developed along Plum Creek at Louviers. Currently, the city of Littleton does not accept industrial waste. An existing city ordinance prohibits raw industrial waste in the collection system and requires that all waste from industrial customers, not classified as domestic waste, have pretreatment. Water quality standards applicable to Chatfield Lake may require treatment at a higher level and cost for the planned industrial area than would be needed under the "without dam" condition. 2.5^ Temperature. Water temperatures in the South Platte River at the Chatfield Lake site range from about 39•2° F in January and February to approximately 6U.L° F in July and August. Some water has been impounded in the lake area because of construc tion of the embankment. Sampling of impounded water on 1 September 1971 gave a temperature reading of 77° F. The air temperature at this time was 86° F. Sampling was done again on 8 and 9 August 1972. Water temperature readings were 62.8° F and 62.9 F, respectively, while the air temperature was 72° F both days. 2.55 Turbidity. Turbidity readings were taken at the intake of the Kassler plant prior to treatment. Most of the readings for turbidity have been in the range of 2.0 to 10.0 Jackson Units, with an occasional reading as high as 25.0 Jackson Units. The lower readings are by far the most common, and this means the water is quite clear. 2.56 Flows. Flows are seasonal on the South Platte River and Plum Creek. Records are published by the U.S. Department of the Interior, Geological Survey, in cooperation with the State of TABLE 3 SUMMARY OF STATE WATER QUALITY STANDARDS CLASS CTivriion A 1 A 2 B 1 B 2 Settloablc Solids Essentially Free Essentially Free Essentially Free Essentially Free Floating Solids Essentially Free Essentially Free Essentially Free Essentially Free Taste, Odor, Color Essentially Free Essentially Free Essentially Free Essentially Free Italic Materials Essentially Free Essentially Free Essentially Free Essentially Free Oil aid Crease Maximum - 10 mg/1 Maximum - 10 rrc/1 Maximum - 10 mg/1 Maximum - 10 mg/1 Drinking V.’ater Drinking Water Drinking Water Drinking Water Radioactive Material Stanlards Standards Standards Standards At or Lelcw present At or below present At or below present At cr below present Sal in it*/ levels levels levels levels Gearotric Moan of Gecmetric i-*aan of Geometric Mean of Ckaiotric .'Vaan of . Fecal Colifom Bacteria 200/10Qml fran fiv e 200/lGCfr.l frem fiv e lOOO/lOOml fran fiv e lOOO/lOOml from fiv e sair.ples in 30-day per. sea-pies in 30-day per. samples in 30-day por.R.'imnle3 in 30-day per. No increase of more Uo increase of more No increase of more lio increase of mere Turbidity than 10 J.T.U. than 10 J.T.U. than 10 J.T.U than 25 J.T.U Dissolved Oxygen 6 mq/1 minimum 5 mg/1 minimum 6 mg/l minimum 5 mg/1 minimum Maximum of 110% of Maximum of 110% of Total Dissolved Gas Pressure atmospheric pressure atr.ospheric pressue PA 6.5 - 8.3 6.5 - 8.3 6.0 - 9.0 6.0 - 9.0 Maximum 63°F. Maximum 2QSF Maximum 68°F. • Maximum 90°F. Tcsrpcrature Maximum Change 2°F. Maximum Orange: Maximum Change 2°F. Maximum Change: Streams - 5°F. Streams - 5°F. Takes - 3°F. lakes - 3°F. Streams-max. 100 ug/1 Streams-max. 100 ug/l Streams-max. 100 ug/1 Streams-max. 100 ug/1 ; Phosphorus as P InV.es -max. 50 ug/1 lakes -max. 50 ug/1 lakes -max. 50 ug/1 Lakes -max. 50 ug/1 Monthly average of Monthly average of Focal St-it.( uxx>ceus 20/10Qml fran five 20/lQQml fran fiv e — — samples in 30-day per. samples in 30-day per. Colorado. The following. information is "based on records for recent years from cages on the South Platte River at Littleton, Colorado and on Plum Creek near Louviers, Colorado (7.5 miles from the mouth). 2.57 Maximum and minimum flows of record for the two streams are as follows: South Platte River at Littleton, Colorado Maximum: 110,000 c .f.s ., l6 June 1965 Minimum: 7.2 c .f .s ., 2 October 1956 Plum Creek near Louviers, Colorado Maximum: 15^,000 c.f.s., l6 June 1965 Minimum: Ho flow 2.58 South Platte River flows are normally low from August through April; however, occasionally a rainstorm or the melting of a plains snow cover has occurred and resulted in significant runoff. Maximum annual flows usually occur from May through July and are the result of mountain snowmelt runoff. These flows are often augmented by rainstorms which occur during this season. Plum Creek flows are usually low throughout the year, since very little mountainous area is drained by this stream. High flows occasionally occur as a result of rainstorms or low elevation snowmelt. These high flows are usually of very short duration and are most lik e ly to occur in May and June. 2.59 pH.. The pH of the South Platte River wrater in the Chatfield area is within the limits set for a potable water supply. At the Kassler Mater Treatment Plant • intake, pH readings are typically 7.5 to 8.0. 2.60 Ammonia (NIL.). Concentrations of ammonia in the South Platte River waters above Chatfield, based on tests conducted by the Denver Board of Mater Commissioners, range from a low of zero to a maximum of less than 0.001 milligrams per lite r (mg/l). This is considerably below the Public Health Standard and the Denver goal for a potable water supply. . 2.6l Nitrate (IIO^). Reported combined concentrations of nitrates and nitrites in the South Platte River upstream from Chatfield averaged 0.10 n g / l d u rin g th e p a st 2 y e a rs . The maximum record ed during this same period vas 0.20 mg/1. This is within the Public Health Standards and the Denver goal, both of which specify a maximum of 10.0 mg/1. They are also within the lim it of 0.30 mg/1, which is accepted as the maximum allowable concentration over which nuisance algae growths can be expected. 2.62 Phosphates (P0j(). Concentrations of total phosphorus in the South Platte River waters for a 2-year period averaged 0.05 ng/l. The maximum recorded was 0.30 r;'T/l. The Denver goal is to reduce phosphates to 0 .5 0 mg/1 for finished water supplies. The commonly accepted standard for phosphates, over which nuisance algae growths can be expected, is 0.02 mg/1. 2.63 Dissolved oxygen. Dissolved oxygen levels at Kassler and in samples of water presently impounded in Chatfield have ranged from 7.9 to O.lj mg/l. 2.6^ Algae. Host of the algae reported in the Kassler plant are filter-clogging diatoms. Other species with potential for causing odors have been noted; however, these algae have not reached con centrations that could be considered a problem. Generally, con centrations of less than 500 organisms per lite r of water cause no trouble and 500 to 1,000 organisms cause little or no trouble. In a ll but 2 of the 2h-month period from Kerch 1970 to I-'arch 197^, the average con centrat ion s were below 500. Even though no serious a,lgac problems have been noted in the South Platte River, this does not mean that problems could, not develop in Chatfield lake. Since the lake w ill act as a nutrient trap, nutrients w iil be recycled through the lake food web, thereby concentrating them in the lake water. This is normally a slow process and with the high quality water of the Couth Platte River, it is anticipated that considerable time w ill pass before nuisance algae growths occur. This would be on the order of 20 to 30 years or more. The likelihood of problem algae growths occurring w ill increase as the area surrounding Chatfield Lake become developed. This is due to runoff from these developed areas which w ill contain chemicals (plant nutrients) that can stimulate aquatic plant growth.. For the present, however, the Couth Platte River water is of sufficiently high quality to offset local runoff problems. 2.65 bacteria. At the Kassler plant, coliform counts show seasonal fluctuations, with the highest readings in late summer (August). The number of total coliform organisms per 100 m illi lite rs (ml) of water typically varies from 2.0 to 3.0 during the winter months to from 200 to 300 during July and August. Fecal colifom readings are 0 or close to 0 for 5 or 6 months of the year; the August 1971 high vas 8.8 organisms per 100 ml. The State of Colorado Standards for coliform bacteria are shown in table 3. TIT. RFLATIORGHIP Qv TTTD PROPOSED ACTION TO LAND UCTl PIARS FOTEIiTIAL IMPACT AREA 3.01 Figure 1 shovs the area upstream from Chatficld Lake; it is assumed that the lake w ill have potential impacts on this area. The following discussion centers on the secondary impacts of the lake on the study area. PCFJLATTO:; CROUTH AID LAID UGE 3.02 Figure 2 is a sim plified land use suitability nap prepared for the Denver Regional Transportation D istrict (RTD) in the publication An Ecological Planning Gtndy, January, 1972. The figure shovs the study area is located in an area moderately suited to urbanization and pasture!and. The foothills to the vest are unsuited for urbanization while the areas to the north and east are good urban and good agricultural land. These factors show a significant preferability for urban growth to the southwest Denver area. 3.03 The Denver R e g io n a l C o u n c il o f Governments (RRCQG) adopted plan policies for the metropolitan area in June 1973 in which the following statement is made: "Many of the studies conducted by the Joint Regional Planning Program taken as a whole, suggest that new development should essentially be discouraged from a northeasterly direction. Much of the region's major air pollution is found in the Platte Valley to the north of the Region. Major amounts of the best agri cultural soil in the Region also exists in the Fortheast sector of the Region. Major flood plains and aquifer recharge areas also exist in that area. "Major development is also to be discouraged in the direct westerly direction from the Metropolitan Area. Areas of extremely high winds exist along the foot h ills areas, as well as slope conditions not pro pitious for large scale residential development. VJater, sewer, and other community services are hard if not impossible to provide. The foothills and major mountain areas of Colorado exist as one of the most beautiful amenities in the Region. They should be kept in a natural state. "Development should remain contiguous vith existing urban areas to minimize disjointed and scattered public facility costs and development. Haphazard development in areas several miles from the fringe of existing urbanization although initially cheaper for the developer and buyers, ultimately must be provided vith urban facilities and amenities that cost more to provide over a large area. That cost is ultimately absorbed by public funds. "Development in a non-contiguous and haphazard manner makes the provision of public transportation facilities difficult and costly, adding to the number and length of auto trips from those areas. The lengthening of these trips causes increased levels of air pollution as veil as increased investment in public roads." The area that meets the dual requirements of suitability and contiguity is located in southvest Denver. Current trends indicate that thi3 area is one of the fastest growing areas in the region. The study area is located in three DRCOG dis tricts. The 1970 population in these districts was 8,71^. DRCOG projects a 2010 population for these districts of 32U,U57. 3.0^ Figures 3 to 6 present facilities to accommodate growth in the area. Gas and electric lines, water and sewer service areas, transportation and transit plans, and employment centers indi cate the extent to which the area will be urbanized in the future. 3.05 Although the study area (Chatfield Lake project) will have an impact on growth in southwest Denver, the natural and planned growth of the area, sewer, water, and transportation facilities, and employment centers, are presently causing growth on a larger scale. Growth of the study area is minor in comparison. The recreation area creates open space in an urbanized area and is consistent vith regional and local plans. . AUTHORITY TO CONTROL GROWTH 3.06 The authority to control growth is significant, mainly in those areas unsuited for urban development. The foothills on the vest side of the study area have mostly unsuitable soils. They are rocky or gravelly on the hogbacks, mesas, and flats. In many places the soils are characterized by swelling clays. Clays and mudstones are exposed in the gullies that dissect the foothills region. 3.07 Unsuitable areas in the south and east portion of the study area are located in the flood plain. The remainder of the area is suited to urban development and pastureland. Authority to control growth is primarily the responsibility .of local govern ments and, in selected instances, the State government. HB 10^1, passed by the Colorado Legislature in 197^*» enables State financial assistance to be given to local governments for the purpose of designating and policing hazardous areas. Where a "State interest" is involved, development may not be permitted by local government. "State interests" include flood plains and areas of potential instability. 3.08 The unsuitable land on the west side of the study area lies in Jefferson County. Most of this land is located in three large tracts, Pike National Forest, the Martin-Marietta Corporation, and the Ken Caryl Ranch development, shown in Figure U. Pike National Forest will act as a barrier to urban development on the southwest side of the study area. The tract on the west side of the study area is owned by the Martin-Marietta Corporation and is used as a manufacturing and testing area. The plant is shown on land use maps as an employment center while the remainder of the property is shown as open space. The area to the northwest of the study area is the Ken-Caryl Ranch, a 10,000-acre planned unit development owned by Johns-Manville. The master plan for the ranch was approved in October 1972 and is an example of Jefferson County's future action with respect to development in the foothills. 3.09 The approved land use plan included in the Planned Development District limits the reach to 5,500 dwelling units, with a density of less than 0.60 units per acre. This would generate a population at full development of about 17,800. Current development plans, which extend through 1985, limit the development to approximately 1*,000 dwelling units, with an estimated population of less than 13,000. 3.10 Johns-Mnnsville will have two corporate facilities located on the southern portion of the ranch, near Deer Creek Canyon Road. A research and development center is to be located east of the hogback ridge and Johns-Mansville's Corporate World Headquarters, which will be located in the valley, is scheduled for completion in 1976. In addition, a portion of the area east of the hogback has been zoned for office, professional, and other business uses. 3.11 Jefferson County is attempting to control growth through zoning. The use of zoning laws combined with 113 10*41 is currently controlling development impacts of the lake in unsuitable areas and should be adequate in the future. 3.12 The flood plains in the south and east of the study area in Douglas County have controlled development through the adoption of flood plain standards. Under the standards the specific design storm is designated. This designation is used by subdividers and the county in determining areas where flood plain restrictions apply. 3.13 There is nothing in the Chatfield Lake project which is in conflict with these existing plans. In face, the project has two factors which give it special compatibility vith the existing land use plans in the area. These are the recrefation opportunities and the open space which will exist in n.n area which is scheduled for urbanization. IV. THE ENVIRONMENTAL IMPACT OF THE PROPOSED PROJECT ENVIRONMENTAL IMPACTS - provide flood control - increase recreation opportunities - maintain open space - lead to changes in water quality - change fish and wildlife populations - change rates and overall amounts of sand and gravel extrac tion within project boundaries provide scientific and educational opportunities - disrupt existing scenic resources - loss of existing riparian vegetation - loss of agricultural production - temporary loss of tax base - loss of hunting opportunity BENEFICIAL IMPACTS DISCUSSED lt.Ol Flood control. The flood history of the South Platte River in the Denver metropolitan area includes 21 floods since 1814U. Because of channel improvements in some reaches and major changes in the economic characteristics of the flood plain during Denver's more recent history, most of the historical floods are not indicative of the current flood damage potential. The 1965 and 1973 floods, however, are indicative of current flooding potential. The 1965 flood resulted from high-intensity, short-duration rainfall cn only a few tributaries. The 1973 flood, in-contrast, resulted from longer duration rainfall, plus runoff from snowmelt. The 1973 flood generally stayed within the banks through Metropolitan Denver and caused a minimum of damage there. The 1965 flood, on the other hand, is the flood of record in Denver on the South Platte River; it caused exten sive damage. As a result of the 1965 flood in the Denver area, 13 human lives were lost, 2,033 homes were damaged or destroyed, 612 business establishments were damaged, and 167 mobile homes were damaged or destroyed. Total damages were estimated at more them $325 million. It.02 The Chatfield project has been designed to prevent such an event from recurring on this reach of the South Platte River or on Plum Creek. It was developed primarily for flood control. The Chatfield project was designed for much more severe flood conditions than those of the 1965 flood. The average annual benefits attributable to the Chatfield project are $21,1+29*600. This includes $19»39**,600 for flood control and $2,035*000 for recreation. Average annual benefits are for the damages which the project would prevent in Denver over the economic life of the project, as expressed on an annual basis. There is also the unquantified benefit of diminished mental anguish associated with the decreased flood threat. 1*.03 With the Chatfield project in operation there still will exist the possibility of flooding within the downstream channel area between Chatfield Dam and Denver. This flood potential is due to tributary inflow within this reach which is not controlled by Chatfield Dam. The proposed downstream channel project, which is currently undergoing restudy, and which will be discussed in a supplemental environmental statement, would alleviate this flood potential. 1+.0U Recreation and scenic attractions. The Denver metropolitan area is deficient in water-based recreation space and facilities. The Chatfield project will fill a portion of the area's recrea tion needs. The 1,150-acre reservoir will provide opportunities for swimming, water skiing, boatingi and fishing. Facilities such as a swimming beach, boat dock, and a marina will be provided for public use. The Chatfield project will also include 5*769 acres of land surrounding the multipurpose pool limits. Much of this land will be developed for outdoor recreational uses. These uses include camping, sport shooting facilities, picnic shelters, hiking, bicycling, and horse trails. 1+.05 Initial visitation is expected to accelerate rapidly during the first years of operation, reaching 1,1+00,000 visitors annually by the year 1978. A maximum saturation point of 2,000,000 visitors anually is expected to be reached approximately between the years 1985 and 1990. 1*.06 As local sponsor, the State of Colorado will be purchasing the water for the lake. The State legislature has appropriated $3 million for this purpose. There is a contract in force between the State of Colorado and the Denver Water Board for $2.9 million for initial filling of the lake. The contract also contains provisions for the Denver Water Board to make up evaporation losses from the lake. Because of the mountainous setting, good water quality, and the expected access facilities, much fishing for largemouth bass, bluegills, erappies, and trout can be expected. It is estimated that about 75,000 man-days of fishing annually will occur on the lake. This contrasts with an estimated 200 man-days which could have occurred annually on the streams that are being inundated by the project. U.07 Open space. In an area that is rapidly developing, the project has created an open space area which will now be pre served as such for future generations. 1*.08 Changes in water Quality. As water enters the lake during times of runoff, its velocity will be reduced and the sediment will settle. This will result in clearer water being released downstream than presently occurs during periods of runoff. I4.O9 The normal operation of the dam, with regard to water releases, is that outflow will equal inflow, up to a maximum of 5.000 c.f.s. During low flow conditions, the rights of down stream water users will be filled on a priority basis. Following flooding conditions, releases will be restricted to a maximum of 5.000 c.f.s. No specific provision has been made for minimum releases. U.10 It is possible that C'hatfield Lake will thermally stratify during the early years of the project. The tendency for thermal stratification of this lake, however, will be negatively influenced by several factors. - The lake is located in a geographic area of dimictic (having two periods of circulation per year) temperature regimes. This will limit the time of development of thermal stratification to the spring and summer months each year. - The lake's physical dimensions, particularly its large surface to small volume ratio, will depress the tendency for thermal stratification. - The cool South Platte River inflows, nixing with the upper lake waters, will reduce the thermal differential between the lake water layers. Jt.ll Eventually the ongoing sediment depletion of the multipur pose pool will reduce the lake water volume and depth to such an extent that the capability of the lake to thermally stratify will be totally eliminated. h.12 Fish and wildlife habitat. In place of inundation of 13 miles of deteriorated stream fish habitat, the Chatfield project will create a permanent pool of 1,150 surface acres, with an average initial depth of about 17*5 feet. Because of.the moun tainous setting, good water quality and reasonably good fish habitat will exist. Species such as largemouth bass, bluegills, crappies, and trout are expected to survive quite well in the lake. U.13 Gravel resources. Ongoing gravel extraction will result in a deeper pool for Chatfield Lake. This means cooler water and potential for a greater-diversity of habitat for fish. A deeper lake will also mean more volume for sediment reserve, thereby increasing the effective life of the lake for recreation. It.lU As stated in Section I, the purpose of gravel extraction in the upstream end of the project is to permit removal of this valuable resource. A side benefit is the creation of additional fish and wildlife habitat. Present plans specify the eventual excavation of nine ponds, varying in size and shape. The area where excavation will take place is shown as a shaded area on plate 5. Estimates of the amounts of gravel to be removed vary widely, but the amounts are substantial. U.15 The ponds that will be created by this gravel extraction will provide additional habitat for fish and wildlife. They will all be located within the nature awareness and environmental study area of the project. No boating will be allowed in these ponds and access to the area will be by trails only. It.l6 Educational opportunities. The Denver Botanic Gardens plans to establish an arboretum and an Americana exhibit in the Deer Creek drainage area. The Americana exhibit will include the Hildebrand Ranch and a one-room schoolhouse. This will provide a link to the past and also provide city children an opportunity to view farming practices and farm animals in a close-in situa tion. The facility would be available for use by individuals, schools, civic clubs, and similar groups as an educational tool. U.17 The nature study and environmental awareness area will be established in the southernmost reaches of the project area. This will give schools, ecology clubs, and interested citizens an opportunity to view nature in a relatively undisturbed setting close to a large metropolitan area. DETRIMENTAL IMPACTS DISCUSSED b.l& Loss of vegetation. The filling of the permanent pool will result in the loss of a number of trees, in particular the large grove of cottonwood trees-containing the heron rookery. Some additional 5,000 acres, which are within the flood control pool, are subject to periodic inundation. The grasses and forbs on these acres probably would not suffer permanent damage from periodic inundations. However, some trees, such ns pines, cannot tolerate extended periods of flooding and would die within a short time. Other trees are more tolerable of minor flooding and may not be permanently harmed during the projected short periods of inundation. 1».19 Recreation. Detrimental aspects of recreational use of the area include the impact of humans, vehicles, and recreation facility construction and operation on the natural environment. ^ .20 Water quality. Impoundment of water in Chatfield Lake will result in changes in water quality in the lake. There are two possible exceptions. One is related to reservoir operation and pertains to a statistical possibility of downstream water quality degradation. Normal operation makes no provision for downstream water quality releases; outflow will equal inflow up to a maximum of 5,000 c.f.s. The pool will be allowed to fluctuate between elevations 5^26 feet m.s.l. and 5^30 feet m.s.l. Average yearly evaporation from the pool is calculated to be about 2 feet. Thus, if the pool were maintained at elevation 5^30 feet m.s.l. at the beginning of a particular year and the evaporation was normal, the pool would still be 2 feet above the minimum eleva tion of 5U26 feet m.s.l. at the end of that year. If during an extended dry season the pool would fall below elevation 5^*26 feet m.s.l., the State of Colorado is to supply the water necessary to replenish the pool to elevation 5^26 feet m.s.l., and also supply any water guaranteed to downstream users. If for some reason this is not physically possible, there would be an evapora tion deficit downstream and water quality would be degraded. Technically, such an occurrence can be linked directly to the lake • and to the increased evaporation loss. However, it is anticipated that such occurrences will be infrequent and will not create conditions significantly worse than what has historically occurred during extended periods of low flows. It.21 The other possibility for water quality degradation is eutrophication, which is also discussed in Section II and earlier in this section. Eutrophication, a natural aging process of lakes, could be accelerated in Chatfield Lake by future development in the drainage area above the lake. Runoff from such development could contaminate Chatfield Lake and lead to abnormally heavy growths of aquatic plants. This, in turn, would lead to a degradation of water quality in the lake and also in the channel downstream. The lake will reduce the velocity of flows of the entering water and, thus, allow deposi tion of sediment. Release of this water from the lake will have a tendency for increased erosion of the downstream channel. Erosion due to this factor will occur until the released water has again picked up its normal sediment load. At this point downstream channel erosion will approximate natural conditions. h.22 Following flooding conditions, releases from the lake will be restricted to a maximum of 5>000 c.f.s. Even prior to reaching this magnitude of flow, however, severe erosion of por tions of the downstream channel could result because of insuf ficient capacity and deteriorated bank conditions. Because of this potential damage, certain alternative solutions are being examined during the study of the downstream channel project. These alternatives are listed in Section VI of this statement. They will be examined in detail in the downstream channel environmental statement supplement which will be prepared after the study is completed. 1».23 Fish and wildlife. The Chatfield project will inundate permanently or intermittently 13 miles of poor stream fish habitat of the South Platte River and its tributaries. The project will inundate permanently or intermittently 13 miles of riparian wildlife habitat. Portions of the 1,150 acres which will be permanently inundated currently have some value as wildlife habitat. Recreation use and development induced by the project will reduce the value of lands upstream from the multipurpose pool for wildlife habitat. U.2k The heron rookery described above will be flooded by the multipurpose pool and will, in time, be permanently lost. The flood plain cottonwood forest in which this rookery is located is also the home for dozens of species of birds and many other animals. The loss of this forest will reduce the numbers of wildlife in the area since they cannot exist without habitat. U .25 Unless specifically prohibited by local authorities, there would be an ultimate loss of downstream open space, wildlife, and wildlife cover, heretofore protected by the periodic flooding of the South Platte River. This would result from pressures for urbanization and other types of development which would probably increase as the Chatfield project becomes operational. With the Chatfield project operational, the existing flood threat would be reduced. U.26 Gravel resources. One detrimental impact associated with gravel resources in the multipurpose pool area is the cessation of gravel removal once the pool begins to fill. Any gravel that remains after the pool fills will not be available for future use. Many feet of sediment are predicted to be deposited in Chatfield Lake over the next 100 years. This sediment would further reduce the chance of utilizing any remaining gravel reserves in the pool area, even after the useful life of the project is past. 1* .27 Other possible detrimental impacts of gravel operations are disturbance of the heron rookery, stream pollution, disturb ance of the riparian ecosystem of the South Platte River, safety hazai'dc, erosion, and building of haul roads to transport gravel away from the excavation site. At this point, disturbance of the heron rookery and stream pollution do not appear to be problems, although this situation could change in the future. U .28 Secondary scenic impact. The source of rock riprap for the upstream face of the dam is located approximately 25 miles north of the project area. Mining operations will result in a scar on the east face of the hogback. b.29 Loss of agricultural production. The major portion of land within the project boundary was used for agricultural purposes at the time project construction began in 19^7. In the interim, agricultural uses have been phased out as lend was needed for construction purposes. Ultimately, upon project completion, all project lands will be dedicated to project operational and recreational use. 1».30 The detrimental effects associated with completion of • construction are air pollution, fuel consumption, possible water pollution, and the redesign of one public use area. It is pointed out in Section VI of this statement that the alternative of suspending construction is not a viable alternative. Air pollution and fuel consumption, therefore, will not be considered further since they are necessary secondary effects of the deter mination to finish the lake. They are recognized as being significant but little or nothing can be done to alleviate their effects. It.31 The plan for facilities development, if implemented, will lead to adverse changes in vegetational patterns and adverse runoff possibilities following precipitation. Facility develop ment will also lead to other problems in waste collection and disposal, road maintenance, and facilities upkeep. The higher the level of development, the greater the inpact on the natural environment and changes in drainage patterns. This would be due to roads, parking areas, and similar developments. b.32 Loss of hunting opportunity. Public hunting will not be allowed within project boundaries after the project is completed. This policy is being implemented for the safety of the general public at the site. Since hunting was limited to a small por tion of these lands, the hunting restriction could be considered a minor detrimental impact. ^.33 Potential tax loss. There are two schools located in the immediate vicinity of the Chatfield project. These schools are the Plum Creek School, located just outside the east abutment, and the school located in the Columbine Hills addition Just west of the spillway. Although these schools are not within the taking area, they probably were affected when the lands required for the project were removed from the tax records. There undoubtedly were students attending these schools that lived within the project area, although this was never investigated. Concern was expressed about the adverse effect of the project on the expansion plans of one school. It is realized that this may be true during the first few years after development of the project. It is believed, however, that as soon as the recreational potential of the project is realized, the surrounding area will become developed at a much faster pace than would have been experienced without the dam. This is evidenced by the many private developments that have sprung up around the Cherry Creek Dam and Reservoir which is located a few miles southeast of Denver. U.35 Effect on urbanization. It is likely that Chatfield Dam will have some effect on future development in the flood plain downstream from the dan and in the area upstream from the lake. As pointed out in Section III of this statement, however, there are many factors which show a significant preferability for urban growth to the southwest Denver.area. Many facilities already exist even beyond the project boundaries and, currently, this is one of the fastest growing areas in the region. The presence of Chatfield Lake is expected to have only minor effects on overall growth in the southwest Denver area. 1*.35 Effect on archeological resources. As pointed out in Withers’ report, Appendix II, some of the known archeological sites are in the multipurpose pool area. These sites will be inundated when the pool fills. The degree of adversity of this inundation depends on the significance of the sites which will be affected. Further investigation of certain sites was recom mended in the report, although the overall yield of artifacts thus far has been quite low. In addition to the sites which will be inundated, it is probable that the project will adversely affect, in some way, the remaining known sites which are not subject to permanent inundation. REMEDIAL, PROTECTIVE, AND MITIGATIVE MEASURES U .36 Loss of vegetation. The project is destroying much of the natural vegetation; this is due to clearing, inundation, and recreational development. To mitigate at least some of this loss, a vegetative management plan was initiated early in the planning process. The purpose of this management plan is to set forth recommendations, procedures, estimated costs, end a sequence for the establishment of a permanent vegetative cover within the boundaries of the Chatfield Lake project, with a few exceptions. The exceptions are the Deer Creek valley, highway beautification, and the landscaping of certain major capital improvements, such as the entrance station, fish hatchery, and the Corps' headquarters facilities. Special emphasis is placed on establishing vegetation which is compatible with heavy outdoor recreation use and consistent with the ecological composite of soil, climate, fauna, flora, and man. This plan is to be used as a guide by the forester for the establishment, improvement, and maintenance of the vegetative cover. The forester or technician referred to is the Regional Forester, Rocky Mountain Region of the USDA, Forest Service, or his designated representa tive. L .37 The vegetative management plan provides a review of • existing natural resources, such as flora, fauna, and geology. It also recommends specific planting prescriptions and designs for various parts of the project and for recreation facilities such as camping units, comfort stations, spot shade and screening, wildlife, and picnic and group shelters. 1<.38 The plan is comprehensive in that it specifies planting for all of the areas of the project on a systematic basis. It also describes the periodic maintenance to be carried out to insure planting success. An example of its implementation was the cutting and clearing of many large cottonwoods in the pool area. These were chipped and the voodchips were stockpiled for later use as an organic mulch, as dressings on bike and foot trails, and as a base for picnic areas. Also, in the vegetative management plan, it was recognized that the heron rookery would be flooded and that the resident birds would eventually require a place to relocate. Therefore, a grove of disease-resistant cottonwoods was planted some 300 yards away. It is anticipated that the herons will move to this new grove when the trees in their present rookery fall. It.39 A space of some 30 acres vas devoted to a "holding area" for native species of trees. One hundred seedlings each of 30 dif ferent species of trees were planted in this space. When these trees grow larger, they will be used as replacement stock. It is thought that such trees should have a high survival rate since they would become acclimated to the area before they are placed in a permanent location. It.1*0 A problem was encountered during the summer of 1973 in implementation of the vegetative management plan, particularly as it applied to the tree holding area. Infestations of rodents, especially the northern pocket gopher (Thononys talpoidcs), were causing serious damage to trees and shrubs. Methods for control of these rodents considered were: (l) controlled underground application of low concentrations of strychnine; (2) relocation of tree holding beds to other areas within the project limits; (3) abandonment of the tree holding areas; (k) the use of indi vidually placed traps; and (5) purchase, on an as needed basis, of replacement stock from nurseries. Other control methods were considered but were deemed infeasible for economic or other reasons. 'These included: (l) the placement of cyanide pellets in burrows; (2) biological controls or deterrents; end (3) no control. U .1*1 Although qualified approval was given to the use of strychnine for control, the Colorado State Forester, upon reevaluating the problem decided to try trapping. About 1*5 traps vere used and over 100 gophers vere killed during 1973. The greatest degree of control vas exhibited in areas where only a few burrows vere detected. In most cases the few gophers involved vere eliminated and the area vas not reinvaded. Even . in areas of heavy infestation, however, control vas successful enotigh to justify the continued use of traps. A biological con trol, which vas tried with unknown success, vas the erection of artifical perches to attract hawks. A few hawks have been observed on the perches, but no evidence of them taking gophers has been recorded. Trapping is planned for 1975> as needed. The use of strychnine has not been ruled out, especially if trapping does not provide sufficient control. h,b2 The vegetative management plan was augmented by the architectural theme recently developed for the Chatfield Lake project. The lake rests in a naturally green river valley with a mountain backdrop. In this setting, building structures are a small part of man's relationship to his environment. Consequently, the overall theme and vegetative plan which developed was "to reduce man's impact on the Chatfield environment so as to con serve and not destroy a natural resource for outdoor recreational use". This theme suggested that the architecture for the project should be "recessive" in character. Since the marina facility is the focal point of the Chatfield project, it was considered to have the theme based on that area. 1* .1+3 The theme recommends maintaining the plains character of the site. It will not be overplanted with trees, but rather, earth sculpturing will be used and the area will be planted with indigenous grasses for screening and shelter. Movement of vehicles will be controlled and sufficient pedestrian pathways will be provided in order to provide the natural grasses with the greatest opportunity to survive. All building structures will be recessive to their immediate surroundings and environment. Roads will be kept at a minimum to limit vehicular traffic, and entrances and through roads will also be limited. U.I4U To help withstand anticipated heavy pedestrian traffic, permanent irrigation will be used to establish turf grasses at sites where heavy use is predicted. Adapted native sod forming grasses (cool and ■warn season) will be used on the balance of lands, possibly using temporary irrigation until they become established. I4.I45 The Deer Creek area will be developed into a regional arboretum where plant breeding will take place and introduced plants will be tested for their ability to survive and grow in this area of Colorado. 1*.1*6 Certain areas, such as the southern portion of the project area, will be preserved intact as nature awareness areas. Minimum development will be allowed so as to preserve the natural character of these areas. 14.1*7 Water quality. Should thermal stratification of the lake begin to develop, the need for mitigating possible adverse effects of it has been recognized. In 1971* the Omaha District made the decision to maintain a pumping device at the site; it would physically translocate bottom waters to the lake surface. In addition, the District agreed to install thermal indicators on the intake structure as an alternate to a multilevel outlet. 1*.1*8 Storm sewers. Storm and combined-sewer overflows can be a source of significant quantities of pollutants. Demonstrated technology to control storm sever discharges does not exist. Efforts are being made to quantify the problem and identify the effect on receiving waters. I4.I49 The combined-sewer overflow problem is better quantified, and FPA research has demonstrated many types of control and treat ment techniques. The techniques fall into five categories: (l) separation of sewage and storm collection systems; (2) opera tional control of the existing system; (3) storage and subsequent treatment; (1*) dual use; and (5) direct treatment of overflows. Combinations of the techniques often result in the most cost- effective solutions, as has been demonstrated in Atlanta, Georgia and Eucyrus, Ohio. U.50 Pollution abatement. Essentially two alternatives exist for the control of urban storm runoff pollution; (l) the con struction of holding facilities for temporary impoundment of storm water overlows; and (2) prevention of pollution at the source. 1*.51 The first choice, construction of holding facilities, is extremely expensive in established areas. For new developments, where runoff holding facilities can be integrated with ongoing development, the cost should be substantially less. U.52 The second alternative of prevention at the source is the less costly effective solution. This alternative involves the use of effective street cleaning operations raid the elimination of catch basins. A combination of education and regulation could prevent pollution caused by the practice of depositing grass clippings, lawn chemicals, grease, and salt where they can be carried away by storm runoff. An interim response which vould be of considerable value in most communities would be to clean out dirty catch basins on a regular basis. This would be particularly effective if they could be cleaned just before periods of major rainfall. U.53 These paragraphs on storm sewers and pollution abatement are included to give an idea of the state-of-the-art with respect to controlling non-point urban runoff. Actually, these problems will result from the rapid urbanization in the southwest Denver area which has been identified as being affected only slightly by the Chatfield project. The ultimate responsibility for controlling this runoff will reside with State and local governing bodies rather than with the Corps of Engineers. U.5U Fish and wildlife. The planting of the cottonwood grove, discussed in Sections II and IV, was done in an attempt to miti gate the loss of the grove presently being used by great blue herons. Ey the tine the trees in the present grove fail to support the rookery, the new grove will he ready for occupancy. Past experience in other states has demonstrated that herons will, indeed, make such a move. Wildlife experts and concerned groups are reasonably confident that the Chatfield herons will make the adjustment when the time comes. 1*.55 The nature study areas in the South Platte River and Plum Creek flood plains will offer significant wildlife habitat. These areas will not be developed for recreational uses other than nature enjoyment. They will be left as is with a minimum of service roads and trails. H .56 The arboretum to be established west of relocated Highway 75 will eventually provide habitat for wildlife. After the vege tation becomes well established, it will naturally attract many birds and other animals to replace those lost during construction. U.57 The lake fishery created by the impoundment will signifi cantly increase the opportunity for development of fish habitat within the project boundaries. • H .58 In the vicinity of the heronry, it will be necessary to curtail gravel extraction during the prenesting and nesting period (March through September), because the herons are very- sensitive to noise during this period. Observers have noted agitation at the arrival of only a few vehicles. The rookery will be surrounded by water and only motorless boating will be permitted in this area of the lake. The new nesting site, which is being readied for the herons, will have no vehicle access roads leading into it. If curious people cause problems in the future, all access to the new rookery may have to be regulated during the nesting period. GRAVEL 1*.59 Existing; resources. Gravel extraction operations within the lake area are, in themselves, a mitigation of a resource that will be lost vhen the lake fills. The upstream extraction is less of a mitigative measure, since the gravel reserves there would not be directly affected by the project. In this upstream region, specific areas have been established for gravel removal. Plans call for an estimated 950,000 tons of gravel to be removed. Should the need exist, the Corps would authorize additional extractions to complete a nature study or environmental area objective. All removal will have to be completed within the next 5.5 years. ^.60 Extraction operations. Several adverse impacts associated with the extraction operations were discussed earlier. Several things are being done which will mitigate the impacts. It.6l Topsoil stripped from areas where extraction is to take place will be stockpiled for later use within the project areas. h.62 The contractors will not be allowed to pollute the stream; they must provide an operational plan which will cause suspended matter to settle out of water before it reenters the South Platte River or its tributaries. U .63 No gravel operations may be closer than 900 feet to the heron rookery during the period of March through September. At no time will gravel removal be permitted within the heron rookery. Other restrictions placed on the contractor are that he must fence the area in which he is working, only certain areas may be used for temporary stockpiles, and haul roads will be restricted to certain areas. The contractor is also required to stay at least 25 feet from any trees and to shape a 50-foot edge of the excavation to a 1 vertical on 5 horizontal slope after operations are completed. Excavation of a particular pond will proceed in an orderly manner, from one side to the other. Seeding specifications, which specify a mixture of wheatgrasses, have teen included in the agreement between the contractor and the Government. U.6U Scenic. To minimize the visual intrusions of the embank ment, the upstream face of the dan is being riprapped with rock of uniform color. The color of the cement used in the intake structure was changed from white to gray to minimize visual con trast with earth, stone, and vegetation colors. k .65 Preservation of open snace. Real, estate purchases for the project included more than 3,000 acres of unimproved rural land. These acres include land with subdivision potential, rural farm land, and creek bottoms. Without the project, the land with sub division potential and a good share of the rural farmland would eventually have been developed for subdivision. With the project, this land will be used for recreational purposes and will con tribute open green spaces for the enjoyment of the public for years to come. h . £ 6 Mining Operations. Control of mining operations for riprap and subsequent reclamation procedures is the responsibility of the Colorado Bureau of Mines. Such measures will include erosion con trol during mining operations, control of rock slides, and slope protection. Reclamation procedures would insure that slopes are graded to approximately the same contours as prior to rock extrac tion and would also specify reseeding where appropriate. U .67 Archeological resources. If interest in the known archeo logical sites at the Chatfield project remains, it is recommended that the University of Denver, and other groups interested in archeological and paleontological resources, strive to complete investigations of the known sites. It does not appear probable that any of the sites are critical enough to warrant special protection upon project implementation and operation. Therefore, it appears that interested organizations should act now to com plete their investigations of these resources. V. ADVERSE ENVIRONMENTAL EFFECTS WHICH CAHKOT BE AVOIDED SHOULD THE PROJECT BE IMPLEMENTED 5.01 All of the riparian vegetation along the streams to be inundated by the multipurpose pool will be lost. Wildlife habitat losses will parallel vegetation losses. 5.02 Thirteen miles of stream will be permanently or intermittently inundated by lake waters. 5.03 There could be an ultimate loss of downstream open space and wildlife habitat without preventative control by local govern ment. 5.0U Water evaporation from Chatfield Lake will amount to approximately 2,500 acre-feet per year. 5.05 There will be some air pollution and fuel consumption associated with completion of the project which cannot be mitigated or prevented. VI. ALTERNATIVES TO THE PROPOSED ACTION ALTERNATIVES 6.01 Operate an a dry dam. Instead of filling the multipurpose pool or allowing it to fill, the project could he operated as a flood control project only, with a dry pool. The dam would he allowed to impound water temporarily during flooding conditions and the water would he released as soon as possible. The low level intake is located at elevation 5335 feet m.s.l., while the channel bed is near elevation 5380 feet m.s.l. Therefore, there could he a small permanent pool of water remaining above the dam. Eventually, this would probably silt in and there would be essentially no pool following release of floodwater. The alternative of a multipurpose pool and associated recreational development would remain open for the future. 6.02 There would be no initial development of a lake fishery resource with this alternative. If gravel extraction were allowed to proceed upstream as planned, the gravel reclamation ponds would fill even though the lake was nonexistent. Filling of these ponds would result from seepage from the high vater table adjacent to the river and from occasional high water during flooding condi tions. These ponds would give the project some fish and wild life benefits even without the main lake. These would diminish in time as they would fill with sediment from high flows during flooding conditions. 6.03 Since most of the planned recreational development centers around the proposed lake, the absence of a permanent pool • would greatly curtail recreational activities at the project. Activities that would remain include hiking, biking, horseback riding, and nature study. Recreation benefits from these remaining activities would be only a fraction of the benefits of a completed lake project. 6.0U Although the lake would be operated as a dry pool under this alternative, it would not be advisable to plant permanent woody vegetation in the pool area. . The water from a large flood may not recede for several weeks. Most woody vegetation would die within this time span. Therefore, a cover of grasses and perennials would seem to be the best interim cover for the pool area. Even these may have to be largely replanted following flooding conditions. 6.05 This alternative would not be fully responsive to one of the authorized purposes of the project, recreation. It would not relieve a significant portion of the area's water oriented recreation demand. This would be a significant adverse effect. 6.06 If small ponds of water remained in low spots following catchment of floodwaters, these could become breeding places for insects. In order to avoid this condition, the pool area would have to be graded to provide proper and complete drainage to the intake structure. 6.07 Operate the project for flood control and water supply. The embanlanent and spillway would be completed, and the pool would be filled to the normal operating level for this alterna tive. This pool would then be used for municipal and industrial water supply in lieu of recreation. This would mean that initially up to 2U,000 acre-feet of water would be available for such use. There are some problems with such an alternative. The volume of available water is not large and will decrease as incoming sediment displaces the water. It is not possible to increase the storage capacity without infringing on the flood control storage and thus reduce its effectiveness for this pur pose. Storage capacity would have to be increased by constructing a new dam if the underlying strata could support it. Such an alternative would not be responsive to the increasing need for public recreation facilities, particularly in this part of the Denver area where rapid urban development is expected. Another factor which must be noted is that the substitution of water supply for recreation would have to be authorized by Congress and could not be done without special studies to show that such use would be in the best public interest. Since there would be no development of recreational facilities, very little or no recreation activities would occur there. Most of the recreation benefits, which amount to $2,035»000 annually under the alterna tive being constructed, would not be realized under this alter native. All, or essentially all, of the costs of recreation development would be saved. 6.08 A decision would have to be made concerning implementation of the forest management plan proposed for the project. A portion of this is designed to improve and enhance the various recreational and comfort features planned for the project. This portion would not be needed if recreation development was not implemented. Certain other portions of the plan are mitigative in nature and could be put into effect whether recreational development was implemented or not. 6.09 It is questionable whether or not this alternative would allow the developnent of a lake fishery. Although the water would be available, its use for water supply nay preclude its use for fishing, both because of quality and quantity conflicts. At this point in project construction, public awareness is such that it would be extremely difficult to keep recreational uses from occurring on project lands. Practically speaking, there would be other adverse impacts to this alternative. It can be supposed that the public would attempt to make trespass-use of the land and water resources of the project. Without proper health and safety facilities, such use would be extremely detrimental to project resources. In addition, the health and safety of the users could be in Jeopardy unless the proper precautions and safeguards were provided. 6.10 Do not finish construction. Under this alternative all remaining construction would be suspended. Construction of recreation facilities and the relocations would remain uncompleted. 6.11 Construction of access roads and certain facilities could be suspended without irreparable harm resulting to the downstream areas. Although this construction might more properly be con sidered under one of the above alternatives, it is a part of the initial project. Providing access without providing roads and facilities to control use would result in obvious environmental damages; these damages would be caused by the type of vehicle movement and recreation activity that occurs in uncontrolled recreation areas. There ore a number of relocations of utilities that are 3till under construction. To cease work would, no doubt, cause some disruption of public services and would result in public outcry. 6.12 Although removal of existing construction is technically possible, the Corps would not fulfill the obligation that Congress has directed; this obligation is to provide flood control and recreation to the residents in the South Platte River basin. In addition, the money already spent and the money required to remove the existing construction would be lost. Although the land could be returned to private ownership, it is unlikely that such action would result in any environmental savings. In fact, there is no reason to assume that the returned land would not be converted to some urban use from its present open space and agricultural use. All of the uniqueness of the area would be lost, including the heron rookery. Under such an alternative, essentially all of the economic benefits of the project would ■be lost and there would be no long-term environmental or social gain. 6.13 Other alternatives not currently under consideration. The above four alternatives represent the current alternatives available for consideration. Several alternatives which were available for consideration prior to the beginning of construction are listed here for information only. For one reason or another, none of them are currently viable. 6 .lU Alternate dansites both upstream and downstream from the Chatfield site. These included the Bureau of Reclamation’s Two Forks site and various combinations of the Chatfield site and one or more other sites. 6.15 Development of sites farther upstream would have required multiple embankments, would have been more costly, and would have controlled a smaller portion of the drainage basin. For these reasons, such alternatives *; -e discarded. 6.16 Two possible sites farther downstream from Chatfield were analyzed. Both sites would have required an embankment greater than twice the length of the chosen site. More urban area, more railroad line, more miles of highways, and higher value agri cultural lands would have been involved. Problems of higher costs, extensive relocations, and additional engineering problems precluded further consideration of these two sites. 6.17 Downstream channel modifications. Basically, this alterna tive proved to be economically infeasible. Structural costs alone for a project which would provide adequate flood protection to Denver would have been greater than for the selected alterna tive. When other costs such as relocations, lands, bridges, interior drainage, and additional miles of unlined channel were added, the costs were clearly not Justified when compared to the benefits received. In addition to the high costs, such a project would merely have transferred the flood problem downstream from Denver. 6.18 Evacuation of the flood plain downstream from the Chatfield site. Because of the high degree of development in the flood plain of the South Platte River, the costs of evacuation would have far exceeded the flood control benefits to be gained. For this reason, plus the obvious political problems which would have been involved, this alternative was not given further con sideration. 6.19 Flood proofing of structures and bridges in the flood plain downstream from Chatfield. For reasons similar to the evacuation of the flood plain downstream from the Chatfield site, thi3 alternative would have been economically infeasible. Due to the great number of structures in the flood plain, flood proofing of all of these would have been a monumental task and may not have been entirely adequate. For these reasons, this alternative was not given further consideration. 6.20 South Platte River, Chatfield to Denver. The information presented in this section will be discussed in greater detail in a future supplemental environmental statement. 6.21 The embankment of Chatfield Dam was completed in 197*<. Consequently, the Chatfield Lake project is not structurally capable of becoming a fully operational flood control reservoir. The presence of this project will have notable effects on the downstream channel and the flood plain of the South Platte River. Although Chatfield Dam has removed the threat of the more severe flood,events which have been experienced in the past, problems of flooding and potentially serious erosion still remains for this stream reach. 6.22 Normal operational functions for the flood control aspects of Chatfield Dam will be accomplished by the Corps of Engineers in conjunction with the Colorado State Engineer. When inflow conditions are such that the pool level is within the multipur pose pool elevations, the mutually agreed upon operation calls for inflow to equal outflow up to 5>000 cubic feet per second (c.f.s.). The Colorado State Engineer will provide guidance during this normal operating situation to satisfy the rights of downstream water users. No specific provisions have been made for minimum releases. The H-foot buffer zone in the multipur pose pool, however, could conceivably be used for lov flow augmentation if minimum releases were desired. Floodvaters, which would result in outflows in excess of 5,000 c.f.s., will be stored in the flood control portions of the reservoir and released at a Jater date. 6.23 Flooding between the Chatfield Lake project and Denver can result from the operational releases from Chatfield Dam or from • runoff entering the river downstream from the dan. At several locations,- the existing channel capacity is less than the maximum operational flows which can he released from Chatfield Lake. Less frequent, but flow's of greater magnitude, can be experienced from runoff originating downstream from the dam. 6.21* Prior to construction of the Chatfield project, stream- borne sediments from the upstream portions of the basin provided somewhat of a balance by replacing bed and bank materials lost due to stream erosion. This natural process of transporting alluvial materials was interrupted with the closure of Chatfield Dam. Water released from the Chatfield Lake will be essentially sediment free and will have a tendency to pick up a sediment load from the existing streambanks and streambed. Most of the natural banks consist of an easily erodable mixture of sands and gravels. Bank-full stages have produced severe bank erosion at some locations. High sustained flows will be experienced during periods of flood pool evacuation of the Chatfield Lake project. The combination of sediment-free stored waters and longer periods of high flows will predictably cause greater erosion problems than have been experienced in the past. 6.25 Experience at similar projects demonstrates that such flood and erosion hazards are generally disregarded if not taken into account early in the project life. If these hazards are disregarded in this case, existing property in the flood plain could ultimately be damaged. Alternative actions are presently being examined for the South Platte River between Chatfield Lake and Denver. These alternatives are being presented to affected local interests to obtain their value Judgements regarding the concepts. The alternatives currently under con sideration are: - No action. This alternative assumes no structural measures or flood plain regulations to reduce existing and future flood and erosion losses. - Flood plain acquisition. This alternative would include the acquisition of all land and development within the 100-year flood plain. - Channel enlargement. Three design capacities are under consideration: 5.000 c.f.s., 100-year dis charge, and standard project flood discharge. - Standard project flood levee. This alternative would include channel enlargement and levee con struction to control the standard project flood. “ Intermittent standard project flood levees. Levees would be constructed to protect existing develop ment from a flood of standard project flood magnitude. - Flood plain regulations and insurance. This alter native would be consistent with the requirements of the Flood Insurance Act of 1973. - Flood proofing. Existing and future development would be flood proofed to prevent damage from channel erosion and flooding. - Combination of measures. This alternative would consist of two or more of the measures presented above. Such an alternative could include flood plain acquisition, channel enlargement, and levees. 6.26 As previously mentioned, these alternatives will be fully discussed in the supplemental environmental statement on the downstream channel project. All known impacts, detailed descriptions, and pertinent economic data will be presented in that document. V I I . LOCAL SHORT-TERM USES OF MAN'S ENVIRONMENT VERSUS THE MAINTENANCE AND ENHANCEMENT OF LONG-THU-! PRODUCTIVITY 7.01 Project lands total 6,919 acres. About 2,1+50 acres had potential for gravel extraction and about 3>500 acres were devoted to agricultural uses, or were in river-bottom land. Without the project, these land uses would have remained about the same for some time. There would have been a gradual decrease in the acreage of agricultural land and a corresponding increase in land developed for residential and commercial uses. Gravel extraction would have continued to take place and would have increased in activity a3 the needs of the metropolitan area grew. The Chatfield area seemed to be quite productive with respect to this resource. 7*02 Since this project is located adjacent to a large metro politan area, anticipated long-term uses are mostly socially and economically oriented. Exceptions are the heron rookery, which would continue to be utilized for come indefinite period, the riparian woodland at the southern end of the project, which would remain rich in plant and animal species, and the streams within the project area, vhich would retain their stream character until development overtook them. With the project, all of these will change to some degree. The present heron rookery will cease to exist within a few years as the inundated trees fall. If things work out as planned, the herons will move to a new grove of trees which is being established nearby. If the herons choose not to relocate to the new grove, this resource will be lost. This would be the loss of a potentially long term resource for a short-term flood control benefit. The riparian woodland at the southern end of the project would not be greatly affected by the completion of the Chatfield project, if access to the area is restricted. With a minimum of disturbance, this area could remain productive for a period far beyond the expected economic life of the project. 7.03 Without completion of the project, or more precisely with removal of completed construction, the various streams of the project area would not be inundated with reservoir waters. They would retain their stream character well into the future. Further economic development of the area within the Chatfield project boundary could alter water quality and riparian habitat. Ever, then, however, the basic stream character would remain. With completion of the Chatfield project, approximately 13 miles of stream would be lost forever. VIII. IRREVERSIBLE AND IRRETRIEVABLE COMMITMENTS OF RESOURCES WHICH WOULD BK I SOLVED IN THE PROPOSED ACTION SHOULD IT BE"iMPLnffiHTED 8.01 The lands on which the embankments and spillway are located, and those lands which are being need as sources of borrow mate rials,. could not be returned to preproject conditions at a later date. The 1,150-acre sediment pool will be filled with as much as 20,000 acre-feet of sediment by the time the project's 100- year economic-life has been reached. This area could not be returned to preproject conditions at that time. 8.02 The trees comprising the Great blue heron rookery are located in the upstream end of the proposed lake. These trees are expected to die sometime after impoundment, and to fall within 10 to 15 years thereafter. 8.03 Also committed to the project are the 13 miles cf stream fish habitat, which will be inundated by the reservoir, and the 13 miles of riparian wildlife habitat adjacent to the streams. 8.0U The labor and material resources which arc being used to finish construction of the embankment, the spillway, and the other permanent structures of the Chatfield project will be lost. 8.05 Water evaporation from Chatfield Lake, which will amount to approximately 2,500 acre-feet annually, will be an irretriev able loss associated with the project. 8.0o Unless specifically prohibited by local authorities, there will be sn ultimate loss of downstream open space and wildlife heretofore maintained by the periodic flooding of the South Platte River. Completion of the Chatfield Dam ’would remove restrictions imposed hy the existing flood threat and, thus, allow this loss to occur. IX. COORDINATION WITH OTHERS PUBLIC PARTICIPATION 9.01 A public hearing was held at Denver, Colorado on 29 October 1956 in connection with an investigation for flood control and related water resource development in the South Platte River basin. A complete transcript of the testimony presented at the hearing is on file in the office of the District Engineer, Omaha District, Corps of Engineers. 9.02 The total registered attendance at the hearing was 8l per sons, consisting of farmers, ranchers, and landowners of the basin, representatives of the interested towns and counties, the State of Colorado, regional development associations, industry, the Bureau of Reclamation, the Soil Conservation Service, the Bureau of Public Roads, and the U.S. Fish and Wildlife Service. 9.03 The District Engineer, Omaha District, Corps of Engineers, conducted the hearing. He opened the proceedings by reading the authorizing resolution, summarizing prior reports, reviewing the provisions of legislation pertinent to flood control and other - water resource development, and explaining the scope of the cur rent investigation. The hearing was then opened to the presenta tion of testimony by these present. 9.024 Oral statements were made by 26 persons and 31 written statements were submitted. In addition, nine photographs of flooding in the Sand Creek-Toll Gate watershed were furnished. Without .exception, all written and oral statements expressed a strong belief in the necessity for immediate flood and water resource investigation and planning.' The predominant statements showed a majority favor flood control only as it can be inte grated or correlated in overall basin development for all other water uses. Due to the divei’se geographic and economic nature of the flood problems, as well as the competition for water resources, there was no unified agreement as to the type of improvements desired. There was sentiment expressed for flood control reservoirs on the tributaries to serve nultipurposes: for irrigation impoundment, the storage of water for winter power development, municipal and industrial water supply, fish and wildlife use, and for recreation. There were other state ments that expressed a desire for local levees, channel improve ments, and the delineation of the flood plain so that zoning could be considered. 9.05 It vas feared that since most upstream reservoirs had been filled to capacity, a repetition of the 1957 flood conditions vould bring a major disaster. During 1957, flood damages had been considerably mitigated by the ability of these reservoirs, relatively empty from drawdown during the preceding drought, to contain much of the runoff. Consequently, the consensus of those present at the hearing vas that immediate action vas desirable. Complete cooperation vas offered by all Federal, State, and local organizations. 9.0o The Colorado V/ater Conservation Board chaired a public meeting in Denver on 19 Uovember 19b5; the Corps of Engineers vas invited to make a presentation. At this meeting, the District Engineer outlined the Corps' propospj.s for flood control in the South Platte River basin, specifically addressing the Chatfield project. The primary purpose of this meeting vas to explore public opinion on construction of this project. There were over 600 persons in attendance, including congressional representatives, landowners, citizen groups, businessmen, and other interested groups and citizens. There were perhaps 80 to 100 statements presented in support of Chatfield Dan. In addition, there were 12 petitions, containing 150 signatures each, presented in srip- port of Chatfield Dam. These petitions cane from various parts of the State. There vas only one krovai person, a landowner, against the project. Fore detailed information concerning this meeting can be obtained from the archives of the Colorado Y'ater Conservation Board. 9.07 A result of this and other meetings sponsored by the Colorado Y/ater Conservation Board has been an attempt to pre serve the open space concept of the 2 miles downstream from Chatfield Dam. This attempt also includes landscaping to make the channel more attractive. Overall, a good rapport has been estab lished between the Corps of Engineers, the Colorado Y’ater Conservation Board, and the local citizens. 9.08 A public landowners' meeting concerning the Chatfield project vas held on 10 January 19t>7 near Littleton, Colorado. The lands required for the project, methods of dealing with landovnerp, how prices are determined, and other similar items were discussed at this meeting. 9.09 A public information meeting vas held in Denver, Colorado in the Vyer Auditorium of the dovnto’/n public library on 16 i'ay 1972. The D istrict Engineer explained the proposed recreational development at the Chatfield project. Approximately 250 persons were in attendance. The public was invited to ask any questions that were appropriate at the end of the presentation. Typical questions pertained to the Corps' policy of tree removal within the limits of the pool and the quantity and quality of recrea tional development. Members of a special interest group repre senting the sailboat enthusiast presented several suggestions on facilities to be used by them. Their remarks vrere accepted and, wherever possible, vere incorporated into the project's recrea tional master plan. No detrimental opposition to the master plan was in evidence, and the meeting was adjourned in harmony. GOVERNMENT AGENCIES 9.10 The draft environmental statement was sent to the following governmental agencies, and their views and comments were requested. Their comments are summarized below and copies of their replies are attached to the statement as Appendix III. Denver Regional Council of Governments Colorado Department of Highways Town of Columbine Valley, Colorado Division of Wildlife, State of Colorado U.S. Department of Agriculture, Soil Conservation Service Department of Transportation, Federal Highway Administration Colorado Division of V/ater Resources Colorado Water Conservation Board U.S. Department of the Interior, Missouri Basin Region Colorado Division of Planning Department of Housing and Urban Development U.S. Department of Agriculture, Forest Service City and County of Denver U.S. Environmental Protection Agency 9.11 Denver Regional Council of Governments. Comment♦ The proposed land use for the Chatfield Lake area is shown as public access on the Council's Regional Land Use Plan. Response. This is interpreted to mean that the Chatfield Lake project is in consonance with the Council's land use plans; no other response is necessary. 9.12 Colorado Department of Highways. Comment. The environmental statement should discuss the demand placed upon the area's transportation system and the capacity of the system to handle this demand. Response. It is agreed that the project vill increase the traf fic volume and change traffic patterns in the project area. The existing system, hovever, appears to he adequate to handle the anticipated changes. The present system is as follows. Trans continental access is currently provided hy east-vest Interstate 70 and north-south Interstate 25, both of these traverse within 15 miles of the project. A future bypass interstate route, Interstate 470, will be located along the north boundary line of the project; it will connect the two transcontinental routes and provide excellent access to the project. Local access routes consist of U.S. Highway 85, paralleling the eastern boundary of the project, and Colorado State Highways 121 and 75, serving the westerly portions of the project. Highways 85 and 121 are two-lane end hard-surfaced; Highway 75 is a four-lane, ninimum- access type road. All are considered to be adequate for the life of the project. Titan Road and Roxborough Park Road vill provide less than desirable access routes to the project during the initial public use period of project operation. Titan Road is two-lane and hard-surfaced; hovever, Roxborough Park Road is only gravel-surfaced at the present time. It is anticipated that as public use increases, Roxborough Park Road must be hard surfaced in order to provide a safe, dust-free access route; this must be accomplished by local interests. Comment. There is concern that the development of Chatfield Lake will induce secondary impacts of increased residential and com mercial development in proximity to the lake. Response. The Corps shares this outlook and this secondary impact has received some attention in the final statement. Comment. The Corps is encouraged to select the alternative that would maximize the recreational opportunities for the region's citizenry. Response. The exact meaning of this comment is not known. The Chatfield project is designed to provide diverse recreational opportunities for an ultimate annual visitation of 2,000,000 people. The development of facilities at the Chatfield project took into account the present population, population or growth trends, needs of the area, and types of recreation most suited to the site. The proposed recreation development is believed to be the best use of the project based on present conditions. 9.13 Town of Columbine Valley, Colorado. Comment. The Board of Trustees of the Town of Columbine Valley expresses concurrence vith the statement. Response. None necessary. 9.1^ Division of Wildlife. State of Colorado. Comment. Although the opportunity for public hunting was minimal on private lands prior to the project, it is felt this opportunity could be significantly increased with controlled hunting after project completion. Response. As stated in the Master Plan for the Chatfield Lake project, a policy of no hunting has been established on project lands. This action is taken in the interest of public safety and in accordance with Title 36 of the Federal Code of Regulations. Wildlife propagation programs, such as wildlife cover plantings and feeding areas, will be developed to encourage wildlife species to find refuge on project lands for the enjoyment of the visiting public. It is still maintained that the loss of hunting opportunity is one of minor proportion. 9.15 U.S. Department of Agriculture, Soil Conservation Service. Comment. On pages 1—1* and 3-15 of the draft statement, it would be better to use the term adapted rather than native grasses for revegetation. Response. This is a valid comment. Since in any case we prefer to use native grasses for revegetation, the term has been changed to adapted native grasses. Comment. In reference to rare or endangered species of fauna, it is requested that the source of the status be given. Response. This is also a valid comment. Not only is the source of the status given in the final statement, but the list has also been updated. 9.16 Department of Transnortation. Federal Highway Administration. Comment. On page 3-2 the statement mentions annual flood control benefits of $17,891,000; it is assumed that this includes some mitigation of damages to roads and bridges in the present flood plain. Response. It vould be more correct to say that this figure includes protection of roads and bridges in the flood plain.. Comment. The bridges through the Denver area should easily handle 5,000 c.f.s.; never structures are designed for 9,000 c.f.s. with freeboard. Response. The 5,000 c.f.s. fig u r e is the maximum planned release from Chatfield Don. However, the discharge from a 1-percent flood occurring downstream from the dam is approximately 17,200 c.f.s. at Hampden Avenue. This w ill be discussed more fu lly in the South Platte River, Chatfield Dan to Denver Supplement to the Chatfield Lake statement. Comment. The statement should address bank erosion problems along the Platte River Drive, South Santa Fe Avenue, and the Valley Highway. Response. These erosion problems w ill be discussed in the environmental statement supplement mentioned previously since they apply more directly to that portion of the project. Comment. The statement mentions estimated visitation of l",V00,000 by 1978 and a peak of 2 ,0 0 0 ,0 0 0 between 1985 and 1990 which could have a significant impact on the approaching road system . Response. Thi,s is a valid comment. The potential impact on area roads has been evaluated. Results of this evaluation indi cate that a ll roads w ill be adequate for the life of the project. Fore specific discussion on a sim ilar comment from the Colorado Department of Highways can be found in paragraph 9.12 of this statem ent. Comment. The statement should, include the proposed transportation plan for the Chatfield Lake area and any impacts thin project would have on the transportation plan. Response. The transportation pattern within the Chatfield project boundary is addressed in detail in the Chatfield Raster Flan and does not present a significant impact. The impact of the project on major transportation routes in the area has been discussed in paragraph 9*12 and does not appear to tax their carrying capability. Finally, it does not appear that the project w ill significantly affect traffic in nearby residential areas. The basis for this belief is that the majority of persons visiting the project viii arrive via the major transportation routes vhich already exist and are located so that traffic patterns are from residential areas to the major routes and then to the project. At no point is there any significant increase in traffic on residential streets because of the project. 9.17 Colorado Division of Water Resources. Comment. In the discussion of gravel operations, it appears that a water surface of approximately 600 acres will be opened up over a 7-year period. This additional surface does not appear to be a part of the anticipated 1,150 acre recreational pool, and the additional evaporation loss does not appear to be accounted for in the projected evaporation loss of 2,500 acre-feet per year from said recreational pool. In short, it seems the addi tional gravel removal operation in the upper reaches of the permanent pool has the potential for damaging downstream water users through increased evaporation loss at least in the amount of 1,300 acre-feet per year. This amount of consumptive use could be very damaging in dry years and I feel the project should be prepared to make replacement for such losses. Response. It is acknowledged that the gravel reclamation ponds which will be created upstream from Chatfield Lake will add to the projected evaporation loss. As with the lake itself, however, the Federal Government is not liable for this loss. It is also pointed out that downstream water rights are a State responsibility; consequently, it is the State's responsibility to determine who is liable for such loss. In order to clarify the matter of pool filling and replenishing, paragraphs cn initial filling and sub sequent operation have been rewritten in the final statement. 9.18 Colorado Water Conservation Board. Comment. The State of Colorado has previously agreed tq.act as the sponsoring agency for the improvement of the South Platte channel below the Chatfield Dam, and has executed an agreement with the United States to this effect. * Response.* No response necessary. Comment. In connection with that stretch of the river from Chatfield Dam to Coal Mine Road, we have previously endorsed and continue to endorse your alternative described as the Littleton Plan. This is the only alternative which has been endorsed by the board. Response. No response necessary. Comment. In connection with that stretch of the river from Coal Mine Road to Vest Hampden Avenue, this hoard endorses your alternative No. U which provides for channel enlargement to accommodate an intermediate regional flood. It is the only course of action listed in this statement which is acceptable to this board. We do request, however, that this channel enlargement be coordinated with the plan3 of the city of Englewood to con struct a public golf course along that section of the river lying generally between Oxford Avenue and Hampden Avenue. Rptnonse. The coordination requested in this comment has been accomplished. 9.19 U.S. Department of the Interior, Missouri Basin Region. Comment. The statement recognises that severe erosion of down stream portions of the channel will result from releases following flooding conditions. The mitigative measures to reduce this impact should be an integral portion of the statement and not addressed in a "downstream channel environmental statement supplement". Response. The Corps acknowledges that the impacts of the required 5,000 c.f.s. discharge from Chatfield on the downstream area have not been addressed. The following decisions and events have led to the present position. It was the decision of higher head quarters to combine the discharge requirement of Chatfield Lake with those of a previously authorized flood control project on the South Platte River into a single project recommendation. However, realizing that this recommendation would be operation ally tied to Chatfield Lake, it was the decision of higher headquarters to prepare a single environmental statement. Subsequent delays were encountered in arriving at a recommenda tion for the downstream project. Consequently, at the direction of higher headquarters, the environmental statement was prepared addressing the impacts of the remaining lake construction and its operation and maintenance. This left the addressing of downstream impacts to the supplemental statement which will be prepared at such time'as a recommendation on that solution con be made. Comment. What flood control measures are contemplated between West Hampden Avenue and Fort Morgan? Response. The Omaha D istrict, Corps of Engineers, is currently involved in an overall study of water resources and wastewater management for the Denver metropolitan area. Part of this study w ill be directed toward exploring flood control alternatives for the portion of the South Platte River in question. Until the results of the study are known, no specific flood control measures are contemplated for that reach. Comment. Pertinent portions of the referred to Taster Plan for Chatfield Lake and the "vegetative management plan" should be incorporated into the statement. Response. Considerable data, os well as plates, were extracted from each of the documents in Question and inserted into the draft environmental statement. It is believed that sufficient pertinent information has already been extracted, even through this may not have been readily discerned by the reader. Comment. No established or studied units of the Rational Park System appear to be adversely affected by the proposal. Response. Hone necessary. Comment. The proposed does not appear to adversely affect any site registered as a National Historic, Natural or Environmental Education landmark, or any site listed as eligible for such registration. Response. None necessary. Comment. The final statement should reflect consultation with the Federal Register for 19 February 197^, which is a composite lis t of National Register sites up to that date, a r.d a ll subse q u e n t monthly supplements. Response. A paragraph lias been added to the fin al statement to reflect consultation with the 19 Febru ary 197^ Federal Register and the subsequent monthly supplements. Comment. _The environmental statement should establish whether the project w ill have an effect on a National Register listin g. Where this is found to be the case, the procedures relating to compliance with Cection 106 of the National Historic Preservation A c t o f 19^6 ( P .L . 89-665) and Executive Order 11593 become o p e ra tiv e . Response. Five separate cites located on project lands and one site located adjacent to project lands contain single buildings or groups of buildings which appear to have historic significance worthy of future preservation and possible interpretation. A ll sites and buildings which possess apparent historical value have been submitted to the Colorado State Historian in accordance with P.L. 89-665 for possible confirmation and inclusion in the National Register of Historic Places. In the event the State of Colorado Historical Society designates any or a ll of the five proposed historical sites for future preservation, appropriate enhancement features, such as interpretive signs, \n_ll be in s t a lle d . Comment. The statement does discuss archeological, historical, and paleontological surveys made some years ago. It should indi cate what further surveys are contr."-plated in advance of activities which irretrievably commit resources to implement the Chutfield Late project. There have been advances made in the techniques used to study lands possessing potential cultural resources. The statement should also indicate what action w ill be taken to salvage any significant remains found once the project is started. Response. No further surveys are contemplated at the present time or in the near future. Previous surveys did not seen to indicate major finds in the reservoir area and the known sites have been carefully examined. If any significant finds are made before the project is finished, work w ill temporarily be halted or diverted until the significance of the find can be assessed. Comment. Discussion of the cultural resources in the Chatfield Reservoir area is both inadequate and inaccurate. Response, ’dithers' 1972 report was consisted in preparing the final statement. This is the latest information available con cerning archeological resources of the Chatfield area. Comment. The statement does not discuss potential impact on the cultural remains; no m itigating measures are recommended, nor are any.irreversible and irretrievable commitments of the resources recognized. Response. The final statement reexamines a ll potential impacts and, where applicable. proposes remedial, protective, and m iti- gative measures to be tah.cn. Comment. There is concern that the "Criteria for Effect" established by the Advisory Council on Historic Preservation has not been applied to the Hildebrand Ranch. Response. The Hildebrand Ranch is located above the maximum flood pool level of elevation 5500 feet m.s.l. At one time it vas subject to possible attack by vandals; someone was appointed to watch the property for a time. At present the Corps is negotiating a lease vith the Denver Botanic Gardens for the care of the property and buildings. In the interim, the property seems to be in no immediate danger. It is not expected that this area will receive a high enough influx of people to endanger the buildings or their contents. Comment. The comprehensiveness and utility of the report (environmental statement) would be enhanced by appending to it the Bureau of Mines resource study, the referenced University of Illinois study, and the "gravel extraction plan", in addition to adding appropriate paragraphs to sections IV, VI, and VII. Response. The references to the University of Illinois study and the "gravel extraction plan" have been discussed in previous responses. The Bureau of Mines resource study vas consulted in preparing the final statement. However, none of the reports mentioned were appended to the draft environmental statement because it ’./as felt that the text contained enough of their significant detail. This position is still believed to valid. Comment. The statement does not discuss in detail the off-site impacts caused by construction. Response. The access roads, powerlines, pipelines, and other relocations necessitated by the Chatfield project have already been accomplished. It is the purpose of this statement and the intent of BETA to address the impacts of remaining construction, not actions which have occurred in the past. Comment. The main problem with this statement is that many areas are discussed in an "after the fact", manner. Response. As stated in Section I, this environmental statement will describe the remaining construction of the Chatfield Lake project, the impacts of this remaining construction, and the impacts of the operation and maintenance of the project on the environment. It will also list and evaluate the alternatives remaining open for consideration at this point in time. Comment. Pages 1-9- Gravel extraction does not seem congruent with the proposed heavy use recreation area nearby. There have, though, been extensive landscape, pond shape, end mining restric tions designed for this project (restrictions, 3-18). The nine resulting ponds will be in the flood plain and during high flows would be inundated. This will result in rapid siltation of the ponds resulting in a loss of their usefulness as fishing areas. They would remain as marshes suitable for wildlife habitat. Gravel mining restrictions and mitigation of damage must be strictly adhered to and a strengthening of these restrictions would better protect recreation interest, if the gravel must be mined. Response. The gravel extraction operations affect only a small portion of the project and will be for only a small period of the project life. Therefore, they should have little effect on adjacent recreation activities. Realizing that siltation would affect the useful life of the resulting gravel pit areas, no recreation benefits have been claimed for them. We concur that they will develop into marshes and become more suitable for wild life as time passes. Several meetings have been held with gravel extraction interests to insure that not only recreation interests are protected, but also environmental interests. Comment. The statement fails to dwell on the amount of water that will be available for use and reserve pending the projected increase in development along the site. Along this line, what are the projections for the water reserve utilization and surplus in regard to further development? In addition, will the ultimate growth projection create a problem insofar as availability of treatment and disposal of wastes? Response. The exact meaning of this paragraph is unclear. The possibility of utilizing Chatfield for municipal and industrial water storage is discussed in the final statement. If the meaning is something other than this, then this office has not provided an answer. Comment. The Department is unaware of any Public Health Standards for phosphates; the source of this data should be identified. Response. It has been verified that there are no Public Health Standards for phosphates. The final statement has been corrected to indicate this fact. Comment. Concern is expressed that the Corps is not consistent in stating reasons vhy Chatfield Lake will not become stratified. Response. To begin with, it was stated that thermal stratifica tion is possible. Several factors were presented which would negatively influence this phenomenon. At this point in time, the ultimate fate of the lake cannot be predicted with 100 per cent certainty. However, several indicators, which are presented in this statement, are known, and these form the basis of our current thoughts on the possibility of thermal stratification. Comment. With respect to the heron rookery and gravel mining, the present 900-foot buffer area around the rookery does not seem large enough considering the noise and disturbance caused by the heavy machinery used in gravel extraction. Response. This 900-foot buffer zone was determined by a com promise between those who wished to mine gravel and those people knowledgeable about the herons. Certainly a larger buffer zone would be appreciated both by the herons and by members of the Denver Field Ornithologists if it could be arranged. It is pointed out that the herons nested successfully in 197^ despite the gravel operations. Comment. Air pollution and fuel consumption, necessary secondary effects, should be given greater emphasis in the statement. Response. The final statement devotes somewhat more space to these topics, although it is still maintained that these effects are relatively minor in nature. Comment. Page 3-16, paragraph 1: It is stated that the water quality of the South Platte River is sufficiently high that nuisance algal blooma will not occur. If this is true, then adverse effects from thermal stratification should not occur and destratification, if it can be accomplished on a lake of that size, would be unnecessary. Destratification for the purpose of preventing hypolimnetic anoxia may cause an increase in primary production due to the introduction of nutrient rich bottom waters or increase turbidity by bringing up the bottom waters, which would be higher in suspended solids. An increase in the annual heat budget could also be expected; this would change the downstream fauna. Aeration of the anoxic hypolimnion would seem a better alternative should any measures need to be taken. Response. In 1971 the Omaha District, made the decision to main tain a pumping device at the project which would physically translocate the bottom waters to the lake surface. In addition, thermal indicators are to be maintained on the intake structure. These devices are to be alternates to m ultilevel outlets for the purpose of maintaining water quality downstream. Comment. The alternative of providing municipal and industrial water storage at Chatfieid Lake, end its relationship to the pro posed Two .Rorl’.s Reservoir, needs to be discussed. Resnonsc. This is a valid comment; this alternative is discussed in detail in the final statement. 9 .2 0 Department of Housing and Urban Development. Comment. The department offered several supportive comments concerning the flood control and recreation benefits of Chatfieid Dam as they related to IT'D activities in the Denver metropolitan a re a . Response. Do response is necessary. 9.21 Colorado Division of Planning. Comment. The relationship of the Chatfieid Dan to the Bureau of Reclamation's proposed Two Forks Dam and Reservoir must he more thoroughly assessed. Response. In light of several comments concerning the relation ship between the two projects, the fin al statement contains a discussion of this relationship. Comment. An assessment of alternatives concerning the down stream flood plain should he part of the draft environmental statement as the ’’Chatfieid project” includes the area between the dam and Hampden Avenue. The flood plain alternatives can not be assessed independently of the dam. Response. It is agreed that the two portions of the project can not be assessed or discussed separately. This is why it was decided to write a Supplement to the Chatfieid Lake, Colorado L’nvirortnental Statement. In effect, these two documents, although circulated separately, constitute only one environmental statement. The reason that these two documents are being c ir culated separately is to satisfy funding requirements for the lake portion of the project while reformulation of the plan for the downstream portion continues. Comment. The Clearinghouse supports the Littleton Plan proposal as it would be contributing to the multipurpose benefits and uses of the Chatfield Dam. Response. None necessary. Comment. An assessment of downstream flood plain alternatives is essential, particularly if there would be an ultimate loss of downstream open space, w ild life , and w ild life cover, heretofore protected by the periodic flooding of the South Platte River. Response. It is agreed that such an assessment is necessary. Cur regulations require us to conduct such an assessment of the effects of each alternative we consider. The Supplement to the Chatfield Lake Environmental Statement is the end result of this assessment. This document w ill be circulated for review by out side agencies in the near future. Comment. One of the detrimental consequences of Chatfield Dam and Lake w ill be increased pressures for urbanization downstream. One way to mitigate this detrimental effect would be to acquire the flood plain downstream, to prevent the encroachment that could ultim ately defeat the main purpose of the. dam. Response. Acquisition of the downstream flood plain is being analyzed as' an alternative to channel modifications. The cost of such acquisition is much greater than can be offset by benefits which could be derived from such action. Therefore, it is unlikely that this alternative w ill be recommended because the benefit-cost ratio is much less than unity. However, if the State or local governments choose to, they can exercise their authority and restrict development in the flood plain. ?!ore on this alter native w ill be discussed in the supplemental EIS. It is recog nized that Chatfield Dam w ill have some effects on urbanisation and development of the area. However, as Section III of the final statement points out, other factors already are responsible for significant growth in this area of Denver. The addition of Chatfield Dam w ill not significantly increase the growth poten tia l of the area. Comment. The secondary, or indirect, consequences of the Chatfield Dam and lake must be discussed. Response. It is recognized that the draft statement was weak in this area. The final statement dees contain discussions of the known significant secondary impacts of the project. Comment. The impact of the Chatfield Dam and Lake on "land use, water, and public services of the area in questioii" (CEQ guidelines paragraph 1500.fi, 38 CFR 20053) must be assessed. Response. These subjects have all been assessed in connection with the Chatfield project. Whether the results of these assessments appear directly in the environmental statement is related to their significance. However, more discussion was included in the final environmental statement on these impacts. Comment. The impact of the dan and lake on the Hildebrand Ranch is not assessed. The Corps of Engineers should notify the Advisory Council on Historic 1 reservation as required by the Historic Preservation Act of 1966 and Executive Order 11593 regarding measures to be taken to protect the Hildebrand Ranch and other historical and cultural resources affected by the dan and lake. Response. As mentioned on page'2-16, this ranch has been nominated to the Rational Register of Historic Places. In the interim, the resident engineer has arranged for someone to watch the farm and to try and keep vandalism at a minimum. Comment. How.were the benefits assigned to the dam project actually determined? Response. The wording on page 3-2 has been changed to make the meaning clearer. The benefits consist of the damages which the project would prevent in Denver over the economic life of the project. Through a statistical analysis, these are broken down to an average annual equivalent in order to compare them to average annual costs. Comment. The vegetative management plan mentioned on page 3-12 of the draft statnent should be appended to the statement. Response. Since the Forest Management Plan, as it is properly referred to, is some 150 pages in length, pertinent portions of it were referenced in the draft environmental statement. It is felt that this is sufficient also for the final statement. As a matter of fact, the Forest Management Plan is already an Appendix E to the Master Finn for the Chatfield project. To attach the Master Plan including all appendices to the environ mental statement vould make it an ungainly document. Comment. Where is the riprap material "being mined, and are any mitigative measures being taken in connection vith this mining? Response. All of the riprap material is being mined at the Specification Aggregate, Inc. pit, Golden, Colorado. The site is located in Section 15, T-^-S, R-70-W, Jefferson County, Colorado, At the time the nine vas first opened, the scar was visible. Since that time additional mining has proceeded further back into the hillside and is not visible from a distance. Thus, the initial opening of the mine caused a visual impact, but continued operation of the mine will not further degrade the area visually. Comment. Who are the "experts" anticipating that the herons will move to the new nesting area? Response. Generally, the people of whom we are speaking are the Denver Field Ornithologists and personnel from the U.S. Fish and Wildlife Service. In addition, our expectations are based on experiences with Great Blue Herons in South Dakota and in Montana. In Montana, for example, a heronry moved three times as a con sequence of timber cutting. Relocation always fell within a radius of 1,100 yards. In South Dakota, heronries were established in dead cottonwood trees. Comment. Will 900 feet be an adequate distance to buffer the heron nesting activities from the gravel mining operations? Response. A much greater distance would certainly be desirable in this instance. However, the 900-foot distance was chosen as a compromise between wildlife people and the gravel producers. It represents the absolute minimum distance although, as pre viously mentioned, greater separation from gravel mining opera tions vould be appreciated by both the birds and the wildlife personnel. It is again pointed out that 197^ was a successful nesting season for the herons. 9.22 U.S. Forest Service. Comment. On page 1-8, in the last paragraph, please change "... Forestry Department" to ". , . Forest Service ..." Response. This has been done in the final EIS. Comment. The $1.5 million non-Federal cost does not include the $3 million budgeted by the State of Colorado to fill the multi purpose pool and replace evaporation losses. This needed invest ment is directly related to recreation benefits. Response. This is a valid comment. Table 1 of the final environ mental statement includes the $2.9 million as a non-Federal con tribution. This figure is part of the total project cost. Comment. The effect of the Bear Creek project on South Platte River floods and the size of the multipurpose pool and recreation use capacity that could be maintained should be analyzed. Response. These factors have previously been discussed in the final environmental statement for the Bear Creek Lake, Colorado project. This statement vas filed vith the Council on Environ mental Quality in February 1972; it is currently being evaluated for possible update. Comment. Other recreation uses besides consumptive uses should be discussed in the statement. (Ref. page 2-13.) Response. This is not a valid comment since this section is a statement of without project conditions. Section h of the final statement discusses planned and potential recreational uses of the completed project. Comment. The provision of significant recreation opportunities so close to an urban area is favorable from the standpoints of energy consumption and accessibility for the economically dis advantaged. Response. We concur. Comment. On page 3-12, first paragraph, the last sentence should read "The Forester referred to is the Regional Forester, Rocky Mountain Region of the USDA - Forest Service, or his designated representative. Response. This has been noted in the final statement. Comment. Is it possible to modify project operations to protect downstream habitat from severe bank erosion and other adversities. If this is not possible, could project funds be used to armor the more sensitive locations? Response. There is a project proposed for the area downstream which, when completed, would provide flood and erosion protection between Chatfield Dam and Hampden Avenue. This is stated in the draft statement on page 1-2. The final statement has been expanded to more fu lly explain the operation of Chatfield Dam and its effects on the downstream channel area without the down stream project. Since the lake portion and the downstream por tion of the project are interrelated, the effects of the downstream portion w ill be discussed in a supplement to the lake statement when a fin al downstream project has been selected. Comment. It is fe lt that the statement could be strengthened by additional information relating to recreation planning for the general area affected by this project. Response. An attempt was made in the draft statement to provide brief but comprehensive coverage of the recreation planned for the project. This discussion has been expanded in the final statement to supplement this information without adding unneces sa ry b u lk . 9.23 Department of Planning, City and County of Denver. Comment. Section V of the statement discusses some side effects of operation of Chatfield Dam. Based on these comments, it is suggested that our department be given an early opportunity to monitor the development of the downstream channel supplemental environmental statement. Response. Your department w ill be given an opportunity for review of the draft supplemental statement when it becomes avail a b le . Comment. The department requests that up-to-date 100-year and standard project flood outlines and profiles be included in the final environmental statement. These profiles should describe in detail the flood threat below the dam u ntil such time as channel improvements, if any, are performed in the reach between the dan and Denver. ’ • Response. The requested flood outlines and profiles are not available at the present time. J'o plans for their immediate preparation exist since conditions are changing so rapidly on the South Platte River. Cur present plans do not call for any permanent impoundment of water in Chatfield u n til the spring of 1977, at the earliest. It is conceivable that construction of the downstream charnel project could begin in the fa ll of 1977. Based on this information, it would not be wise to expend large suns of money developing maps which would be applicable for only a few months. . 9.2U U.n. Environmental Protection Agency. Comment. The secondary impacts of the project on population growth, land use, u tility services, and environmental degrada tion in the drainage area above the dan have not been adequately discussed. The analysis and descriptions of secondary impacts must be expanded to present a general overview of such impacts on the drainage area above the (Sam. The FIB should analyze the adequacy of Federal, State, and local legal authorities and plans presently available to control secondary impacts. The FIS should detail the governmental actions which must he taken to adequately prevent and control adverse secondary impacts. Response. This was considered a valid comment. The fin al state ment includes an expanded discussion of secondary impacts as suggested. Comment. The EIS would be improved if there were a b rief, general discussion of the preventive and m itigating measures that might be utilized by governmental agencies in the long run to control non-point water quality impacts resulting from urban development in the drainage above the dam. • Response. This was considered a valid comment. Section IV of the final statement contains a brief, generalized discussion of some m itigative and preventive measures which can be taken to control pollution from urban storm runoff. Comment. Where and how w ill the State of Colorado obtain the water supply necessary to replenish the pool to elevation 5^26 feet m .s.l., and also supply any water guaranteed to downstream users? How w ill the reservoir be operated if Colorado cannot for some reason replenish the pool to elevation 5^26 feet m .s.l.? What flow w ill be released \inder this circumstance? Response. A contract between the ftate of Colorado and the Denver Board of Water Commissioners specifies how the pool at Chatfield w ill be maintained. The Denver Water Board w ill fur nish water from tine to time as may be necessary to replace evaporation losses. Come Couth Platte River water rights currently owned by the State will be conveyed to “’he Denver Water Board. Other water rights are already ownea or controlled by the Water Board. Under certain conditions the reservoir may be allowed to fluctuate as low as 18,000 acre-feet, or as high as 2^,000 acre-feet. As a result of severe and prolonged drought periods, the State may give its consent in writing to the Denver Water Board to some lesser storage for a prescribed period of time. In no event shall the contractor have the responsibility to replace evaporation in excess of U,100 acre-feet in any calendar year, As far as releases are concerned, they will equal inflow up to a maximum of 5,000 c.f.s. At the other extreme, if inflow falls to zero then no releases are planned for the period of zero inflow. Comment. Is there data quantification to support the statement on page 3-7 which says: "However, it is anticipated that such occurrences will be infrequent and will not create conditions significantly worse than what has historically occurred during extended periods of low flow"? Response. There are data to support this statement. Surface water data* are recorded from U.S. Geologic Survey stations at various locations on the South Platte River. Extremely low flows occur very infrequently. Another factor which helps to make such a prediction is the planned operation of the reservoir. These two factors considered together should mean that the volume of streamflow below the dam will not be significantly different from that which would occur without the dam. Comment. Your supplemental environmental impact statement dealing with the South Platte between Chatfield Dam and West Hampden Avenue should discuss the impact of various alternatives on waste water treatment facilities. Response. This is a valid comment. The draft statement will con tain some discussion of these impacts. CITIZEN GROUPS 9.25 The Corps of Engineers Colorado Citizen' Coordinating Committee on Environmental Planning (CECEP) has, since 1968, been involved in environmental planning on the Chatfield Lake project. Topics such as the fate of the heron rookery, recreation, architecture, fish and wildlife, vegetation mitigation and enahneement, sand and gravel extraction, and the embankment itself have been discussed and debated. Over the years, CECEP and the Corps of Engineers have worked together on problems at the Chatfield site and have come up with mutually agreeable solutions. Recently this group has undergone a reorganization and renaming; it is now known as the Corps of Engineers Colorado Citizens Committee (CE3C). 9.26 The following citizen groups have commented on the draft environmental statement. The 'Wildernecs Society Denver Field Ornithologists (Hugh Kingery) League of Women Voters Dam the Platte Committee 9•27 The Wilderness Society. Comment. It is suggested that the "open" sector for water use be relocated to the eastern third of the reservoir to eliminate two major drawbacks. These drawbacks are the two water boundaries to enforce, and audible and vave influence the present location would have. Locating the open sector in the eastern arm would affect the least amount of serainatural shoreline, dam construc tion could provide for minimal effect of wake generated by wave action, and the expected major boundary enforcement problem would be reduced by half. Response. This is a valid agrument, at least in pert. However, the relative positions of the three sectors were determined at an earlier stage in the construction of the project. Siting of the two marinas was based on borrow operations for the main embankment. The "open" sector was located in the middle of the lake for easy access to the marina site which was excavated previously. The "wakeless" sector was located in the eastern sector of the lake so as to be contiguous with the already excavated sailboat marina site. These sectors are, thus, firmly established. The boundaries are somewhat flexible, but it would take major action at this point to change their relative positions. Wave action generated by powerboat activity is not expected to affect the shoreline significantly more than wave action from wind alone. Boundary enforcement could prove to be a problem if boaters do not cooperate. If such a problem materializes, answers will have to be provided at that time. 9.28 Metro Denver League of Women Voters Comment. Are projected users of the Chatfield recreational facilities dependent on the proposed I-U70, a six-lane highway? Response. Since it is not known when or if 1-1*70 will be com pleted, this highway was not incorporated into our plans for the Chatfield project. This highway would improve access to the site but the project is not dependent on it. Comment. The League feels that the Joint Regional Planning Program maps should be included in the statement. Response. It is the opinion of this office that such naps vould norc properly be placed in the Denver metro study report since they are not related directly to the Chatfield project. Comment. The statement needs to explore alternative forms of transportation which vould decrease the impact on the area. Response. As mentioned in another response, it is our opinion that the area's transportation system is adequate to handle the increased load created by the project. In addition, the project will accommodate only so many vehicles and then further access ’would have to be curtailed. The predominant method of trans portation to the site will be the private automobile. Even if limited bus service served the project, the overall impact on the access roads and the.project roads vould be little changed. Comment. It is believed that the effect on air quality by visitors to the lake need be known. Response. It is assumed that the reference to air quality here is because of the increased vehicular traffic. This is perhaps a valid concern. However, initially this area may have better air quality than most of the Denver area metropolitan parks due to its location, and due to the fact that most of the planned recreation will be non-air-polluting. As urbanization gradually surrounds the site, air quality nay -degrade a a later date. At this time, the air quality is not expected to be bad enough to call attention to or to alarm a great number of people. Comment. It vould be advisable to do a complete environmental assessment of a larger area, and then to assess the overall impact on such an area. Response. The Omaha D istrict is currently involved in a •wide- ranging study of the Denver metropolitan area. It is known as the Urban Regional Study of Uater and Related Land Resources; it is scheduled for completion in December 1976. This study incorporates na.ny of the smaller Corps projects in the Denver area into a much broader concept. However, since the Chatfield project was underway before the urban study began, it was not included in the urban study as a needed item. The urban study does fu lfill the need for an overall environmental, social, and economic assessment as it relates to water resource needs. Comment. Since careful consideration must be given to using Chatfield Lake as a source of municipal and industrial water, the wisdom of continuing a recreational project which may have to be abandoned or destroyed due to incorporation of such changes is questioned. Response. From time to time throughout the history of the Chatfield project the subject of municipal and industrial water storage has been discussed. Ho decision to incorporate municipal and industrial storage at Chatfield has been made. There is built-in fle xib ility in the design of recreation facilities as presented in the "aster Plan for this project. Even so, a reallo cation to penr.it municipal and industrial water storage at Chatfield would have far-reaching effects on recreation currently envisioned at Chatfield. In addition, such reallocation would involve trade-offs between the Two Forks and Chatfield sites involving flood control, recreation, and municipal and industrial water storage. To answer the question of such reallocation of storage would involve a restudy of major proportions. This restudy would include a revised environmental statement. There fore, until such tine ns it is definitely decided that municipal and industrial water w ill be stored in Chatfield Lake, the project w ill continue to be developed as outlined in the ''.aster Plan and Section I of this environmental statement. Section I of the final statement contains a discussion of municipal and indus tria l water storage and relationships between tbe Chatfield and Two Forks projects. Comment. An overall viewpoint of the possible connection between Two Forks*or its equivalent, if developed, and Chatfield Lake appears to be essential. Response. This is a valid comment. For the purpose of this environmental statement, the previous response is considered adequate f o r t h is comment a ls o . Comment. The League believes it is essential to explore main taining a relatively natural setting at Chatfield Lake. This view is taken because the League also believes that long-range ecological values are to be placed above short-term solutions. Response. This is a valid comment and a valid concern. However, in this instance, a relatively natural setting at the Chatfield site does not appear likely. It is reiterated that the upstream end of the project will be designated an environmental study area and, thus, will receive a minimum of disturbance beyond that required initially for gravel mining. The balance of project lands will be devoted to intensive recreational development. Whether or not this is ideal from a long-range ecological view point is a moot at this time, since any changes in project pur poses would require major legislation. Another factor to be considered is the suitability of Chatfield as a natural area. Such an analysis would indicate that the land adjacent to the project is rapidly being developed and, with the exception of the upper reaches of the project, there is not much natural setting left to maintain. 9.29 Huah Kingery, Denver Field Ornithologists. Comment. Some minor criticisms were offered relative to the flora and birdlife information in the environmental statement which vas furnished to the Corps by Hr. Kingery. Response. The final statement has corrected all of these deficiencies where possible. Comment. There in concern that the present gravel mining opera tions are lowering the water table in the vicinity of the heron rookery. If a larg.e number of these trees die prematurely, it may have deleterious effects on the rookery. Response. A representative of the IJ.S. Forest Service escorted a multidisciplinary team, including Hr. Kingery, into the heronry area in June 197^ to assess the dead and dying cottonwood trees. As a result of their observations, it vas speculatively concluded that tree mortality vas the result of a lowered water table. They also stated that other factors may have been contributing to the tree mortality. Their recommendation was to mark the dead trees with flagging and then make another survey in late Hay of 1975 • Since future gravel operations are planned for the South Platte River flood plain, the Omaha District personnel want to insure that-a similar tree mortality will not occur. Therefore, • for all future -gravel mining in or near*the flood plain, more stringent reflations governing groundwater effects will apply. In addition, stringent nitigative measures ara specified’in all • _ contracts let for cravel mining. 9.30 Dam the Platte Committee. Comment. The comittee made a number of generalized statements siipporting the continued construction of the Chatfield Lake project. ' • Response. It is felt that none of the statements made'requires a specific response. Ccrr*e«t_. Statements were also made in opposition to certain nonstructural alternatives being evaluated as part of the down stream portion of the project. Response. Until that study is complete and'the supplemental EID is published, we feel it is inappropriate for us to address the above comment. FINAL ENVIRONMENTAL STATEMENT CHATFIELD LAKE, COLORADO APPENDIX I A Record of Field Observations of the Birdlife of the South Platte River, in the Vicinity of Vaterton, Jefferson, and Douglas Counties, Colorado GREEN RIBBON BIRDS A Record of Field Observations of the Birdlife of the South Platte River, in the vicinity of Waterton, Jefferson, and Douglas Counties, Colorado. by Hugh E. Kingery The green ribbon of the South Platte acts as a magnet for migrating, nesting, and wintering birds on the high plains near Denver. This area has enjoyed little disturbance by man, thus permitting a highly diverse avifauna. The wild character of the river bottom, with its natural stream, tall cottonwoods, wild plums, and tangled thickets, offers a variety of habitats to many different species of birds, filling the varied niches of this environment. Undisturbed by man, many species not ordinarily found close to the city find food and shelter. Listed in this report are 183 species of birds, identified along the river and the adjacent plains and foothills within 5 miles of Waterton. A special feature in this special place is the heronry, close to Chatfield Dam, now under construction. The Corps of Engineers, upon learning of the heronry, has developed a program for protecting it, even though its present location lies within the ultimate permanent pool. This report is prepared for the Corps, and for local ornithologists, as a reference to the diversity which the river habitat offers. DESCRIPTION OP STUDY AREA The South Platte River comes out of the mountains at Waterton and turns northeast on its way from the Rockies to the Gulf of Mexico. In the foothills, before it exits at Waterton, it courses through a canyon bordered by rocky cliffs, brushy hill sides largely covered with mountain mahogany (Cercocarpus montanus and an occasional Rocky Mountain juniper (Juniperus scopulorum), and gullies filled with scrub oak (Quorcus garnbclii) and a few cottonwoods (Populus angustifolia). Abruptly at its exit from the mountains, the river habitat changes into a plains river bottom, marked by healthy groves of cottonwoods (Populus sarpentii). Other significant trees include box elder (Acer ncgundo) and some willows (Salix sp.). Throughout its course, from the canyon to the Chatfield Dam area, it has a substantial undergrowth comprised of many shrubs; most noticeable are the wild plum (Prunus americnna). rabbit brush (Chrysothamnus nauseosus), currant (Kibes aureum), and various willows (Salix sp.). Adjacent to the cottonwood groves are scattered cattail and bulrush marshes, a high plains habitat, and some cultivated farmlands. One field on Titan Road, near Plum Creek, supports a huge prairie dog colony. The cottonwood biorae supports about 1*0 nesting species of birds; the density of breeding birds is very high, Judging by a Breeding Bird Census taken in 1971 in the heronry. The popula tion calculated from that study, 68k birds per 100 acres, equals that of the highest-populated habitats reported throughout the country. The Platte also attracts nany birds migrating across the arid plains. Spring migration produces an abundant variety of species, fall migration almost as many. During and after severe storms, it offers a sanctuary and food for both plains migrants and foothills birds unable to find food. After an early 18-inch snowstorm, the collection of birds around Waterton on October 5» 1969* was dramatic in both variety and numbers. The varied natural habitats provide nesting niche3 for the rich birdlife. The herons, owls, and hawks nest in the crowns of the cottonwoods. Yellow warblers, redstarts, vireos, and kingbirds nest high in the canopy of the trees. Orioles, goldfinches, robins, and pewees nest in the middle elevation of the forest. In the brushy areas and on the ground nest towhees, chats, MacGillivray's and Virginia's warblers, catbirds, and scrub jays. Pheasants and meadowlarks nest in the grassy areas. Hole-nesting birds (usually they use dead trees, but occasionally U3e live ones) include the flickers and dovaiy voodpeckers, chickadees, house wrens, starlings, and screech owls. Migrating birds have similar preferences, with many warblers, tanagers, and finches feeding in the upper reaches of the trees; sparrows, Juncos, and thrushes found in the understory, and along the river, ducks, geese, sandpipers, and the unique dipper (never found away from a running stream). The bird observations which comprise this report come from five years of field work by the author, plus additional observations provided by other local ornithologists. During 1971, four ornithologists, including the author, conducted a Breeding Bird Census using techniques prescribed by the National Audubon Society; this census appeared in the December 1971 issue of American Birds, published by the Audubon Society. FORMAT The format of the report presents the species listed in the taxonomic order of the American Ornithologist's Union. The thickness of the horizontal lines indicates the frequency vith which the bird-watcher can expect to find the species. The graph is divided by month, and the extent of the line shows the time of year the species has been-observed. COMMON— found on at least T5J® of half-day field trips in suitable habitat. FAIRLY COMMON— found on 25? to 75? of the half-day trips in suitable habitat. UNCOMMON— found on less than 25? of the half-day trips in suitable habitat. RARE— observed infrequently; each dot represents on observation, placed to indicate the time of year. Explanation of abbreviations in Denver area status; Seasonal Occurrence. PR-permanent resident, found throughout the year SR-summer resident, breeding in summer and migrating in fall, returning in spring SV-summer visitor, non-breeding WV-winter visitor, from outside area or other life zone in Colorado M-migrant visitor, transient moving through the area Acc-accidental, straggler out of its normal range Abundance scale AB-abundant, seen commonly in great numbers, 500 or more in a single day VC-very common, 100-500 in a single day C-comnon, 25-100 in a single day under proper conditions FC-fairly common, 10-25 in a single day at appropriate time and place Unc-uncommon, 3-10 in a single day and up to 25 per season R-rare, 1-5 in a single day, but no more than 5 per season VR-very rare, no more than 1-3 in a single day and season Ca3ual-seen but once every few years Irr-Irregular STATUS OF SOUTH PLATTE BIP.DS See attached DENVER AREA STATUS______Pied-billed Grebe Two seen in river 10/2/69 SR-FC Double crested Comorant Reported as nesting in heronry many years ago SR-FC Great Blue Heron Heronry occupied since 19th Century; 91 occupied nests in 1971 SR-FC Whistling Swan Pair observed on farm pond 3 mi. SE of Waterson, 11/6/71 M-UNC Canada Goose Hunting pressure must explain relative absence of geese and ducks in the face pp-c Mallard One or two pairs nest along the river PR-VC Gfdwe11 SV-UNC.WV-FC PintaI1 SR-FC,UV-UNC Green winged Teal SV-UNC.WL-FC Blue winged Teal SR-C Sm. Widgeon Found on ponds near the river SV-UNC.WV-FC Wood Duck A pair acted as if it were nest hunting, spring 1971, they nest ir bolls in trees PR-R [Redhead Observed in Chatfield Wash Area, 1971 SR-UNC [Lesser Sceup Observed in Chatfield Wash Area, 1971 SV-UNC,WV-FC Common Goldeneye j VJVC Bufferhead Observed only in Chatfield Wash Area, 1970 and 1971 \ WV-FC [Old Squaw Observed only in Chatfield Wash Area, 1970 WV-Casual ! Common Merganser ' w-C [Turkey Vulture M-UNC [Goshawk Seen once in foothills canyon WV-VR [Sharp-skinned Hawk These three "bird hawks" require dense cover for thei r .hunting, chWV-UNC jCooper's Hawk is usually done from a concealed perch in a tree iRed-tailed Hawk Two pairs of this species nested along the river in 1971. The j nesting birds fiercely protected incursims by man within PR-R j 100 yards of their nests (WV-C) jHartan's Hawk Broad-winged Hawk I An eastern bird which appears regularly in the spring M-R Swanson's Hawk A plains bird rarely coming this close to the mountains SR-FC Rough-legged Hawk Rough-legs may regularly be seen hunting over the open fields WV-FC Golden Eagle The eagle probably nests and winters in the foothills; it can often be seen soaring along the edge of the foothills, in Platte Canyon in times of quiet, and sometimes over the plains river bottom PR-UNC Bald Eagle This winter visitor occasionally soars over the plains. In the I most part it winters on the ice-covered reservoirs and the larse I mountain rivers WV-R Marsh Hawk I Frequently hunts, cruising over fields SR-FC Osprey An endangered species, an Osprey or two each year favors the Souti Platte for a waystop during migration. m -R Prairie Falcon Hunts over open fields, occasionally seen along the river PR-FC PeregnineFalcon Seen once on plains 2 - 3 miles from Waterton m -R Pigeon Hawk I A fast-flying falcon WV-UNC Sparrow Hawk A few nest in holes in trees along the river PR-C Ring necked Pheasant PR-C American Coot Found on nearby lakes and ponds PR-VC Ki 1 ldeer PR-C Spotted Sandpiper I Nesting along the mountain and prairie streams, some may nest I along the Platte SR-FC Solitary Sandpiper M-UNC Common Snipe PR-FC Greater yellowlegs M-UNC Ring-tailed gull The garbage dumps near Hampden Ave. attract thousands of these birds, and they frequently cruise along the river PR-C Franklin Gul1 M-AB Band-tailed Pigeon This species nests in the foothills and stragglers appear along the river bottom SR-UNC(fthi11s; Rock Dove Roxborough Park probably supports a roost of these birds, which range several miles from their roosts in order to feed. PR-VC Mourning Dove A common nesting bird; one nest hatched eggs on the late date of August 18, 1971- The flimsy nests are on the ground in bushes or in trees. SR-VC Barn Owl A dead bird which has been shot found near heronry 11/13/71 PR-VR Screech Owl Probably more common, but nocturnal and hard to find, as are most owls. PR-UNC Great Horned Owl Several pair nest along the river, beginning in February, includirg one in the heronry. PR-FC Pygmy Owl A sparrow-sized owl, rarely seen WV-Casual Burrowing Owl Summer resident in the prairie dog colony on Titan Road; seen once on river on k/2S/SS. SR-FC Long-eared Owl Difficult to find, like most owls. PR-UNC Short-eared Owl An owl of the open fields, not often seennear the city PR-R Common Nighthawk Common night feeder; sometimes found roosting in the cottonwoods SR-FC White-throated Swift Nests at Red Rocks Park and probably at Roxborough Park, and feeds on the river bottom. SR-FC Broad-tailed Hummingbird The males mate, then leave for the high country flowerfields; a few stay around to nest along the river bottom SR-UNC B. Kingfisher A few patrol the r'ver all year, nesting in holes in the stream banks PR-UNC Yellow-shafted Flicker One male of this eastern species wintered near Waterton 1970-71; hybrids between this and the next appears occasionally, including a female mated with a Red-shafted Flicker in 1970. PR-VR Red-shafted Flicker Even though flickers stay here throughout the year, a noticeable migration occurs in the fall; after a heavy snowstorm in 0ct.'69 70 were counted on one day. PR-C Hairy Woodpecker Nests in higher mountains, drops down to plains in winter WR-UNC Downy Woodpecker Many nest in the cottonwoods, in holes in trees. In 1971 a pair shared a nest tree with a pair of flickers and of House wrens PR-UNC Leurs's Woodpecker PR-UNC Yellow-billed Sapsucker One observed October 5* 19^9 M-R Eastern Kingbird A few nest in the cottonwood groves SR-C Western Kingbird SR-C Great Crested Flycatcher One observed 9/18/71 M-VR Say's Rhocbe n on open plains, where it may nest. SR-FC Empidonax Flycatcher Individuals of this genus are usually identified by sound; during migration the birds are usually silent. M-UNC Hammond's Flycatcher M-UNC Dusky Flycatcher M-UNC Western Wood Peewee The nasal call of this common nesting flycatcher is typical of the cottonwood groves in summer SR-FC Olive-sided Flycatcher M-UNC Horned Lark An abundant bird of the open short-grass prairie, but seen only ir small numbers close to the mountains PR-C Violet-green Swallow Substantial flocks of swallows migrate north along the river M-C Tree Swallow M-UNC Bank Swallow SR-FC Rough-winged Swallow SR-UNC Barn Swallow Nests in a variety of locations, particularly around barns and highway bridges SR-C Cliff Swallow Like the Barn Swallow, nests under bridges, although not in the Denver area SR-VC Blue Jay An eastern bird, the Blue Jay has in recent years become a nesting resident in Denver, and possibly may become more common along the Platte. PR-UNC Stellers Jay Common in the Ponderosa Pines of the foothills, it occasionally comes down to the Platte PR-C Scrub Jay Nests in the bushy hillsides upstream from Waterton; occasionally ventures down to the river cottonwoods PR-FC Black-billed Magpie A common, conspiuous bird of the plains and foothills. Its bulky nests are conspicuous in the winter cottonwoods PR-VC Common Raven The status of ravens is uncertain; the White Necked normally is WV-R White-necked Raven not expected in the Denver area, but it may be a regular visitan: Casual Common Crew Occurs in large flocks; on 12/3/67 350 flew up the river canyon in late afternoon, apparently to a roost. PR-UNC Pinyon Jay WV-Irregular Black-capped Chickadee Pairs occur along the river all year; they nest in holes in the cottonwoods PR-FC Mountain Chickadee Common in the Ponderosa Pine belt and above, this chickadee occasionally drops down to the plains in winter PR-C Common Bushtit A few flocks of the tiny bushtit range the brushy foothills in winter, and rarely venture onto the plains WV-UNC White-breasted Nuthatch This mountain bird ventures onto the plains only occasionally; however a pair has been in the heronry grove throughout 1971 PR-UNC Brown Creeper An inconspicuous mountain bird which occasionally feeds on the cottonwood boles PR-UNC House Wren An abundant nesting bird of the river bottom, nesting in boles in trees and among bushy and viney tangles SR-C Winter Wren A rare, difficult-to-see, tiny wren possibly more frequent than the listed observations WV-R Long-billed Marsh Wren WV-R Canon Wren A few frequent the rocky cliffs of Platte Canyon PR-FC Rock Wren A few spend early winter among the rocks and brush of the hills above Platte Canyon SR-FC Dipper A fascinating bird found always along running streams; it jumps off ice floes or rocks to feed cn the aquatic life, even in cold winter days. PR-FC Mockingbird Although it nests east of Denver, it rarely comes into the foothil s S -UNC Catbird Nests in the thickets and dense brush; calls like a cat and sings like a mockingbird SR-UNC Brown Thrasher An eastern bird, at the west edge of its range here. SR-UNC Sage Thrasher Migrates along edge of foothills, found in brush M-FC Robin Nests commonly along the river. Apparently the nesting population migrates south, and northern birds replace them with most winter ing in the foothills SR-C ,V/V-1 r r Hermit Thrush In the fall, as many as 75 birds may be counted along the river M-FC Swainson's Thrush Fairly common during spring migration - up to 25 birds in a day M-C Western Bluebird The October I969 snowstorms drove a large group of this foothills migrant onto the plains; 89 were counted on 10/5/69, feeding on mullein Spring M-UNC Mountain Bluebird A common plains migrant; 22 were with the Western Bluebirds in 10/5/67 M"vc Townsend's Solitaire Typically seen on isolated junipers in the foothills, frequently singing in mid-winter. It sometimes appears out on the plains along the river PR-FC Blue-gray Gnatcatcher One bird, 10/5/69 M-R Golden-crowned Kinglet WV-UNC Ruby-crowned Kinglet Singing in spring, silent in fall, one tiny kinglet feeds among the brush during migration. M-FC Water Ripit A flock of 63 was feeding in an open short-grass field after a 12-inch snowstorm, 9/18/71 M-FC Bohemian Waxwing During their irregular eruptions they appear along the river WV-Irregular Cedar Waxwing WV-Irregular Northern Shrike The fierce though small shrikes are found usually in opencountry; WV-UNC Loggerhead Shrike occasionally they visit the river bottom. SR=FC Starling This invader from Europe nests in holes in the cottonwoods, prob ably driving off other hole-nesting birds like flickers and possibly Downy Woodpeckers. PR-VC Red-eyed Virea A common nesting bird in the cottonwoods SR-UNC Warbling Virea Also a common nesting bird in the cottonwoods SR-R Black-and-white Warbler A tall creeper, with habits more like the Brown Creeper than other warblers M-R Worm-eating Warbler **/29 and V30/67 M-VR Blue-winged Warbler 5/9 and 5/10/70 Acc. Orange-crowned Warbler Common migrant, feeding both in the cottonwood canopy and in the bushes M-FC Nashville Warbler ; Apparently a regular fall migrant M-R Virginia's Warbler’ Common migrant found usually in bushes, especially wild plum M-FC Parula Warbler Apparently a regular though rare migrant on plains; seen once in footh ills M-VR Yellow Warbler ! Common breeding bird, nesting in the canopy SR-C Magnolia Warbler ; Observed May and December M-R Myrtle Warbler i Common spring migrant, rare in fall. One winter record, 12/26/70 M-FC Sudubon's Warbler j Common migrant; nests in Colorado high mountain forests M-C Black-throated Gray Warbler V 22 and V30/67 M-VR Chestnut-sided Warbler Several 5/9/70 M-VR Blackpoll Warbler 5/25/68 Spring M-R Northern Waterthrush 9/12/71 M-R MacGi1lwray's Warbler A few nest in brushy tangles on the river SR-FC Yellowthroat Found regularly in marshes and along stream SR-C Yellow-breasted Chat Common in brush; secretive except when singing SR-FC Wilson's Warbler More numerous in fall than spring M-C American Redstart Common nesting bird in cottonwoods SR-R House Sparrow PR-VC WEstern Meadowlark Nests in fields alongside the river groves PR-VC Bullock's Oriole The deep hanging nests can be noticed all along the stream in winder SR-C Red-winged Blackbird PR-Ab Rusty Blackbird 12/26/59 WV-R Brewer's Blackbird SR-C Common GracKle SR-FC Brown-headed Cowbird These birds cruise the groves looking for nests in which to lay their eggs; the host parents raise the cowbird young, never knowing it's a foreigner. SR-FC Western Tanager M-FC Scarlet Tanager 6/3/25 Casual Black-headed Grosbeak A few apparently nest SR-FC Indigo Bunting 5/9/71. Hybrids between this and the Laguli Bunting have been seen twice (5/23/70; 7/3/71) SR-R | Laguli Bunting Probably nests in low bushes SR-FR | Evening Grosbeak PR-Irregular Cassin's Finch PR-UNC House Finch Abundant nesting bird in Denver; a few winter along the river PR-C Gray-crowned Rosy Finch 'The^e flocking birds which nest in the high mountains range widely WV-C Black Rosy Finch ! from their winter roosting sites in caves and rock crevices WV-R Brown-capped Rosy Finch [ WV-UNC Common Redpoll An occasional visitor from the north - WV-Irregu1ar Pine Siskin A mountain visiting bird, large flocks of up to 50 birds winter on the plains PR-Irregular 1 American Goldfinch A few are present all year; they nest among the cottonwoods PR-FC Lesser Goldfinch Nests in same areas as American Goldfinch SR-FC Green tailed Towhee M-FC Rufous-sided Towhee Apparently our breeding population, migrates south, and is replaced in winter by northern birds; in the fall and spring a hiatus in towhees occurs. Like the robins, the winter towhees are more abundant in one foothills. Both winter and summer their distinc'ive call typifies the river bottom and the bushy hillsides SR-FC,WV-UNC Nesper Sparrow migrates in April on the plains nearby SR-C Lark Sparrow SR-C White winged Junco Typically winters in the ponderosa pine WV-UNC Slate-colored Junco Juncos, known as snowbirds, feed on the ground and among the bushes and weeds V-FC Oregon Juncos The commonest winter junco WV-C Gray headed Junco This, the native Junco, nests in the ponderosa pine WV-FC Tree Sparrow Found in weeds, not trees, in flocks of up to 100 ormore WV-FC Chipping Sparrow Common migrant SR-UNC(Plains) Clay-colored Sparrow Common fall migrant H-FC Brewer's Sparrow M-FC Harris' Sparrow WV-UNC White-crowned Sparrow Abundant in fall migration-on 10/5/69 a high count of 128 WV-FC Golden-crowned Sparrow Present along Plum Creek the winter of 1967-68 WV-Casual White-throated Sparrow WV-R Fox Sparrow WV-VR Lincoln's Sparrow M-FC Swamp Sparrow WV-R Song Sparrow Typical winter resident in brush along the river, frequently singing PR-C Chestnut-callused Longspur Seen on a Christmas Count, December 1957, at the Titan Road prairie dog colony WV-R FINAL ENVIRONMENTAL STATEMENT CHATFIELD LAKE, COLORADO APPENDIX II Archeological Survey of the Chatfield Reservoir, Colorado, 1968 ARCHAEOLOGICAL SURVEY OF THE CHATFIEID RESERVOIR, COLORADO, 1953 MTIOilAL PARK SERVICE HTRCHAS? ORJ'FR 920-115 Arnold Withers Department of Anthropology University of Denver Msy 13, 1 9 7 2 AECH'GOIOGICAL SURVEY OP THE CHATFIELD RESERVOIR, COLORADO -During the sunnier of I9S8 the University of Denver Department of Anthropology' completed en archaeological, survey of the Chat field Reservoir, Colorado area. The purpose of the survey Was to locate all possible archae ological sites from surface indications. Surveying "was done during the dumnero of 1965 end 1966 and sporadically dating back to 19^9 * As one unit of the Ccnprehensive Plan for Flood Control of the South Platte River and its tributaries, the Chatfield Dam and Reservoir was authorized by the 8lst. Congress, Second Session, Public law 516 on Kay 17, 1950. Funds for construction, however, were not appropriated until Congress approved Public Leer 89-689 cn Oct. 15, 19o6. Construction, of the Project is under the supervision of the District Engineer, Osaka District, Corps of Engineers, Ctacha, Nebraska. To t Litch field, Minn, firms, Johnson Brothers Highway and Heavy Contractors and D. H. Blattner and Sons, Inc., were awarded the contracts for the construction of the Chatfield Darn and began initial operations in August, 1967. The cite of the Chatfield Dan is approximately eight miles couth of Denver, Colorado and located on the South Platte River immediately down stream from the confluence of the South Platte River and Plum Creek. The Dan will be a rolled eai’th type to be constructed between tiro bluffs over looking the confluence of the tvo above mentioned waterways. It will be approximately 152 feet high and have a crest length of approximately 1 2 ,7 0 0 feet. Roughly cne-eighth of the South. Platte River Basin’s drainage area will lie above the Chatfield Dan (3,Ol8 square miles of a total of 2^,030 square miles). Other pertinent information concerning the Chatfield Dan and Reservoir: Total Project area: 6,600 acres Recreation area ant1, facilities: 1,315 acres (part of the total Project area) Note: The State of Colorado Trill iris charge of these areas and establish facilities each as it did at Cherry Creek Reservoir, Colorado.' Sediment pool surface area: 1.150 acres Flood control pool capacity: 4,750 acres Capacity reserve for flood control: 215,000 cere-feet Total length of Project: approximately 9^ nilea Closure date: 1971 Actual completion date: 1973 Ore Chatfield Dan end Reservoir is designed to eliminate much of the threat of flood to the Greater Denver Area. A similar Corps of Engineers project, The Mount Carbon Project, to he constructed on Bear Creek vast of Denver Trill virtually eliminate this threat. The area within the Chatfield Erojectaroa^ia currently utilissd in *1 «««•*»• f w l Vtwgf Ui WUt «4V*>«tVW| ^ >i ■ ■ h j ** IT - - cial card and gravel operations, pane and present. Private residences, both in tracts and associated vith snail farms and 5caches, ero a small, part of the total area, but are amorous. As of September, 1958. 31 prehistoric sites hod been located within and adjacent to the Project boundaries. All bf these rites would either bo in undated or endangered by construction, highway relc cation, cr people using the later recreational facilities. A cite designation was given only to those localities that produced identifiable artifacts. Presumably, these sites were car? sites, although only one site, Colo. K:12:lh, had surface indications of a structure; stone enclosures roughly circular in outline. The overall artifact yield was quite l e u . The mora productive sites yielded numerous projectile points, scrappers, zaauos, mertoies, and various other artifacts while the lesser citsa produced only one or two artifacts. Artifacts in thi3 area probably never ware very plentiful end undoubtedly have become even scarcer in recent years clue to the cultivation of rarh of the area end the cloz..i proximity to urban civilization. A rasiclesi "sirroraheafl" collector claims "there never ware any Indiana to speak of in this (ths Project) area." / lib pettezy of a prehistoric nature uaa located to aid in the identifi cation of the inhabitants of the area. Projectile points ranged in type fro a Yiutau to the large, triangular comer'-ncrfcched type. *n approninate . temporal span of 5-10,000 years is indicated for' these sites ca that basis. Rccommenda.t5.cng: A possible early cite (Colo. K:8:50; T6S, E68tf, UH$SEj JTJ£S7) is situated on the east bank of Plum Creak in tko cut of a gravel pit and on the edge of the terrace above the gravel pit. Surface indications are of a late prehistoric nature. Several chips end flakes -core located in the cut of the gravel pit ‘thus indicating a possible early cite. Further testing in the cut should be considered. A definite early site is the Lamb Site (Colo. K:8;^9; l6s, B65’J>lTi^J,JjS25).. At this cite Ifaldo bedel excavated a mammoth ekoletca and Yuran type point that res not in direct association with the skeletal material. (Ucdcl, l$ol, 1£52, 1563, 156^). Colo. K: 12:15* (S6S,R6S'J,SE£S27) is the only site located within the Project boundaries -that hen sir face indications of habitation. A large roughly circular stone enclosure (tipi ring?) van found ca this cito as well as one stemmed projectile point, one slab met ate, 1 end scraper, end an abundance of chips and flakes. Fire pits were also located on this site. A test trench was dug on the cite in ITov. 195^-(?) which choired no cub-surface indications of habitation. However, I believe this could well be one of ths \ ■ more premising cites in this area due to the relatively deep surface coil. ' Further testing should be considered. Colo.L.12:15 ia. located approximately 75 yards nortbwent; of Colo.foS:!**, on. • .the same bench on the-vest bank of the South Platte River# A dirt read onto into the bench between the two Bites and separates them. The only artifacts collected iron K:12:15 vers badly weathered slab rotate in fragments, and four ctcmned corner, notched points. There is a possibility that K:12:15 ia part c f or associated with K: 12 :lb-. This is sccsthirg that will probably never bo teovn, however, os tho K: 12:15 would probably prove -worthless. Another sito on a terrace projection on the vast G ido of thei South Platte River is Colo.K:8:65 (T6S,F.o2Hy Stf£sw£sil). . Two bifacial sasoa, one point or knife fragnent, one end scraper, and chips vero collected there; This particular terrace projection, only one of many in this general area, vac much more productive, artifact vise, than vas tho surrounding area. Judging fro n t the artifacts collected on this site, ihs.ee seems little d o u b t thia v*i3 a camp site. The soil layer is quite thin, asking testing easy, bub ray indicate a lack of stratigraphy. Colo.K:8:i:l (t £s ,F.69^,1^^211) is located near the north bank of Deer Creek one mile vest of the South Platte River. The soil here is quite thin at the top of the slightly rounded knoll ca which the cite is located, bub the coil depth increases greatly ne'arer Dear Creek. Evmsrcus artifacts were collected from the surface including a shaft abrader and a bifacial sano. Chips cad flakes vara numerous. This cite is quite acoesiblo to tho nmateixr "orrcvhecxl hunter" and has probably been looked over, many times. Despite this, the cite has yielded a relatively high number of artifacts and is a quite likely looking site. I would certainly consider testing this site. Colo,2:8:66 (T&S,R69tf»3E&SE£sih) is located en the edge of a terrace near the trust bunk of theSouth Platto River. Each of the currcucding area has been mined for gravel aid. sand. In fact* the coil on K:8:66 is quits sandy, but there is considerably noro soil than in adjacent areas. One aids scraper, a:, uaiuetched triangular point fragment and m ay ckip3 were collected here. Further work here could prove worthuhilo. There are coven sites strung out along a one mile section of Plum Creek. All are on the east aide of the creek; two on the sandy bank area and fiv e cn the adjacent low candy terrace. Colo.K:8:51 (TSSjRo^Jj^JSS^B?) and Colo.2:3:55 (T6S,F68U,w£lt7j~S17) are the tiro "beach*1 s ite s . Together they produced one stemmed corner notched projectile point, tiro end scrapers, and numeroi-is flehes and chips. The location of these tvo sites is such that they Well nay have been washed in and therefore not associated!, with the other five sites. Likewise, the high water of June, 1$&5 cay have mcovered -these s ite s . The remaining five sites, Colo.K:S:52 (T6s,BS85r,EEj^BjS38), COlo.K:3:53 (•E6S,n68W,E4jK^17), Colo. S:8:5h (T63,P£SlI.Si;^^C17), Colo. K:&:$6 (163, H6Si7jtC»^317)*. a/id. Cwlo. K:o:o0 (tow. Jjoow .fc»if*jt7) . f*tr* *'r 'i eft w re*9*? ’ . . . . ■ • .' *' ..... ' ‘ - the edge of the sandy, rounded terrace. They are also quite near the rail" road tracks which will bn relocated. Thus there is a possibility thee© five sites will be disturbed or destroyed. The surface collection from these fire sites is ne t particularly large or out of the ordinary except for a possible fresh water masse 1 ehoU found on K:8 ;5 6 . There rero no viciblo indications of streetor as cn theca five sites. They are a ll cn undisturbed land and are relative 2y unaccessible to the amateur collector. Therefore, the possibility tedets that these five sites, as well ns the two each” sites, ore rdniwal sites; How-over, further examination end testin g , especially o f the fiv e terrace s it e s , might well prove otherwise. The most interacting archaeological information brought cut by this survey i s that almost every cite producing p ro jectile points ccemo to belong to the Archaic Horizon. A nearby Archaic sits in Hccibcro Bark (Colo.K;12:2) baa a radiocarbon Cats of 5780 + l£o years B.?. (Scotty 1 5 6 3 ) These sites plu3 We<‘el*a Lamb Sit© vrold indicate a lens pxs-Woodlond occupation of iha area. On Oat, 5, 1971, a quite unrelated discovery was made by earth moving equipment for the construction of the Chatfleld Dam. A m a m t h skull was discovered son© fifty feet below the original surface. Glenn R. Scott of the U.S.G.S. estimates the age of this fossil to be 120,000 to 200,000 yearn old. Dr. Edward Lewi a, paleontologist with the U.S.G.S., is studying the skull. It reposes in the U.S.G.S. offices in the Denver Federal Center. S i t e s : K 212 *14 IU 3.2:15 K :8:41 K ;8:49 K :8:50 K :8:51 K :8:S2 K:8s!53 K :8:54 K:8:5-5 X :3:56 Ground’ Stone: club Mofcates 2 2 4 Unifaco Shaped Marios 1 1. Bifaco Shaped Llanos Shaft Abradors 1 Chipped.Stones Sad scrapers 1 Side Scrapers ^ Knifoo 1. 1 - Triangular Stemmed Projectile Points 1 ' 4 Triangular- Point Basal Fragments Triangular Points * with Broken Bases 1 X 1 Hammer Stones l l Cores 1 1 1 3 1 '4 3 Chips and Plakos &H _5 —30 1 11 6 6 3 2 4 5 Polishing Stones S h ell 1 F o s s il Mammoth and Bisoii^Bonos 3 %r , O - Crh ' „ •> V, O W* * £> •• • . /• • *;■ r- IC:Gtbw8»* * > .8 :6 9 fo 3 :6 Q .. " » V> K \. r ’CtfcjiCV^’ «;-. .«>c,U4■ w^Vn *.« 1-iJ JvC •iyounu o'c-ono: i Uixlijr.c'5' Shaped *i Hanes ]»i:Cuo3 Shaped i i 1-i"* V-'C* s n.Uib :.lci*:it03 p t C? soni't Aonodors Cnj.pped Stone: hnd ^cropera «■'< i Cic;o Serapo^s _-V , s _ '.IriX.'. o c> •a *1 •> •** .1 1__ i n a n._ uAo.r- Si: Gr;r.icd P r o j g a t:l lo P o in ts 1 ’ incui-ulur Point Hasai ;Ananiaont« I i ? . *?> P/^’ic;* V/.j.th UlO.VJJ i f C O l & J l l iiarnwor Stones C orea « ■& i i s Cnspc- e.r/l F la k e s C$ . S 7 -r> 3 ' n i s , * Polio sfconos ■'— A- ~ ! ■’ Acs o il Farsnoth '■'i':''-T noro.oc FINAL ENVIRONMENTAL STATEMENT CHATFIELD LAKE, COLORADO APPENDIX III Letters received from Governmental agencies, citizen groups and individuals commenting on the draft environmental statement. DENVER REGIONAL COUNCIL OF GOVERNMENTS 1776 SOUTH JACKSON STREET . DENVER. COLORADO 80210.758-5166 May 20, 1974 Mr. C .F . Thomas Chief, Planning Division Department of the Army Omaha D istrict, Corps of Engineers 6014 U .S. Post Office and Court House Omaha, Nebraska 68102 Subject: E l/002-74, Draft Environmental Statement for Chatfield Lake Dear Sir: Reference is made to your letter and enclosure of April 18, 19 74 concerning review of the Draft Environmental Statement for Chatfield Lake in accordance with Section 102 (2) (c) of the National Environmental Policy Act of 1969 (Public Law 01-100). In response to your communication, the Council has reviewed the Statement as it relates to the Council of Governments' concern with areawide planning and development. The Council of Governments appreciates this opportunity to be of service to your agency. Sincerely, Robert D. Farley ' Executive Director cc: Richard Brown - Colorado Division of Planning Mike Davidson - Jefferson County Planning Department COMMENTS ON El/002-74 DRCOG Staff - The proposed land use for the Chatfield Lake area is shown as public access on the Regional Land Use Plan. (May 20, 1974) DRCOG Parks and Outdoor Recreation Committee - The Committee reviewed the environmental statement and had some concerns as to the effect of sand and gravel operations on the Chatfield Lake area. (April 25, 1974) STATE DEPARTMENT OF HIGHWAYS CHAS. E. SHUMATE • EXECUTIVE DIRECTOR DIVISION OF HIGHWAYS D IS T R IC T 6 E. N. HAASE R. E. HEATHCOTE CHIEF ENGINEER DISTRICT ENGINEER May 21, 1974 Mr, C. F. Thomas Chief, Planning Division Department of the Army Omaha District Corps of Engineers 6014 U. S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: We have reviewed your draft environmental statement for the Chatfield Lake, Colorado project, and offer the following comments: 1. If Chatfield Lake is developed into a major recreation area for the Denver Region, the environmental statement should discuss the demand placed upon public facilities, such as highways and other transportation facilities to reach the subject area. The statement should address the capacity of the area's transportation system to handle this demand. 2. Again, if Chatfield Lake is developed into a major rec reation area, will this induce secondary impacts of increased residential and commercial development in proximity to the Lake? 3. We would encourage the Corps to select the alternative that would maximize the recreational opportunities for the region's citizenry. To not do such would be a terrible waste of resources and opportunities. Thank you for allowing us the opportunity to review this document. Very truly yours, E. N. HAASE Chief Engineer By R. E. HEATllCOTE District Engineer cc: Haase-Capron-Cox II. R. Atchison K. C. Francis File (Heathcote/Brasher) Town of Columbine Valley ARAPAHOE COUNTY, COLORADO LITTLETON. COLORADO SO 120 7 9 4 - 2 6 7 4 May 22, 1974 Mr. C. F. Thomas, Chief Planning Division Department of the Army Omaha District, Corps of Engineers 6014 U. S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: This is to report that the Draft Environmental Statement for the Chatfield Lake, Colorado project has been reviewed in its entirety. We find the report to be thorough and complete. The Board of Trustees of the Town of Columbine Valley has authorized me to express its satisfaction and concurrence with the report. Very truly yours, W. A. Newton Mayor :u a t k o" ccLonAin! Jol'fi D, V.ir.dirhocf, GtW-t'ior Di£PAHTMf-Mr OF NATURAL RrsOUHCl S DIVISION OF WILDLIFE Jack R, Grteb. Director ( 0 6 0 R n.-s.'J'A ,iy Dc.’ivpr. CoiomcJo 3 0 2 1 G ^323- 1 l :)2 j May 23, 1974 Mr. C. F. Thomas Chief, Planning Division Omaha District, Corps of Engineers 6014 U.S. Post Office And Court House Omaha, Nebraska 68102 Dear Mr. Thomas: We have reviewed the Draft Environmental Statement (DES) prepared for the Chatfield Lake Project. The DES adequately addresses detrimental impacts on wildlife, as well as mitigative measures which will be imple mented. The reestablishment of the great blue heron rookery which will be destroyed is good. Other measures, such as development of terrestrial wildlife habitat, and controlled gravel operations, will be beneficial. Upon completion of the project additional efforts to benefit wildlife should be made, including provisions for minimum water releases in the South Platte River. We are concerned that no hunting will be allowed within the boundries of the project. The DES emphasized that as a result of the limited amount of hunting opportunity that previously existed, hunting restrictionswhich will be established after completion of the project are "considered a minor detrimental impact. " Although the opportunity for public hunting was minimal on private land, we feel this opportunity could be significantly increased with controlled hunting after completion of the project. Future plans call for action to modify the channel of the South Platte River from Chatfield Dam to West Hampden Avenue. This could benefit wildlife by perserving a portion of the riparian vegetation and natural flood- plain. Acquisition of portions of the floodplain, such as Littleton proposal, together with a combination of other alternatives is laudable. We would like to work with you on Chatfield Lake and the channel mod ifications down stream. We appreciate the opportunity to comment. Sincerely yours, Paul T. Barrows, Chief Environmental Resources UNITED STATES DEPARTMENT CF AGRICULTURE SOIL CONSERVATION SERVICE P.- 0. Box 17107, Denver, Colorado 80217 May 24, 1974 Mr. C. F. Thomas, Chief Planning Division Corps of Engineers Omaha District 6014 U. S. Post Office & Courthouse Omaha, Nebraska 68102 Dear Mr. Thomas: We appreciate the opportunity to review the draft environmental impact statement for Chatfield Lake, Colorado. Our comments are as follows: 1. Pages 1-4 and 3-15: Reference is made to using Native grasses for revegetation. It might be better to reword this to use adapted grasses. 2. Page 2-10: Reference is made to rare or endangered species of fauna. Since there are several "lists" (federal, state, and some organizations), please identify the list which was used. Several species of birds listed in Appendix I are considered threatened species in the federal list. 3. Page 1-4, line 8: "Riker auream" should be "Ribes auream". Please let us know if we can be of further assistance on this project. Sincerely, M. D. Burdick State Conservationist U.S. DEPARTMENT OF TRANSPORTATION FEDERAL HIGHWAY ADMINISTRATION REGION EIGHT BUILDING 40. DENVER FEDERAL CENTER DENVER. COLORADO 8022S May 28, 1974 Mr. C. F. Thomas Chief, Planning Division Omaha District, Corps of Engineers 6014 U.S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: We have reviewed the Draft Environmental Statement for the Chatfield Lake, Colorado project and offer the following comments for your consideration. 1. Page 3-2, the statement does mention annual flood control benefits of $17,891,100 and we assume that this includes some miti gation of damages to roads and bridges in the present flood plain. 2. The statement does mention possible severe erosion problems from post-flood releases of up to 5,000 C.F.S. (Page 3-3) due to a lack of sediment load as clear is released, but this will be confined to the first several miles below the dam and should approximate natural erosion and deposition processes through Denver. The bridges through the Denver area should easily handle 5,000 C.F.S.; newer structure.- nr-:. v' e-J lV, i.OOO C.F.S. with freeboard. 3. The statement should address bank erosion problems along the Platte River Drive, South Santa Fe Avenue and the Valley Highway. 4. The statement mentions estimated visitation of 1,400,000 ,by 1973 and a peak of 2,000,000 between 1985 and 1990 which could have a significant impact on the approaching road system. 5. The statement -hould include the proposed transportation plan for the Chatfield Lake area and any impacts this project would have on the transportation plan. Sincerely, W. H. Baugh Regional Federal Highway Administratoi By: Frank S. Allison, Director^ Office of Environment & Design JOHN D. VANDERHOOF C. I. KUIPER Governor State Engineer DIVISION OF WATER RESOURCES Deportment of Natural Resources 300 Columbine Building 1845 Sherman Street Denver, Colorado 80203 May 29, 1974 Mr. C. F. Thomas, Chief Planning Division, ATTN: MROPD-ME Omaha District U. S. Army, Corps of Engineers 6014 U . S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: This letter is to advise you of my comments concerning the Draft Environmental Statement for Chatfield Lake, Colorado, which was for warded to Mr. Ten Eyck by letter dated 7 May 1974. While the draft appears to be well done, I do see one potential problem which could be damaging to senior Colorado water-users down stream of the project. In the discussion of gravel operations, it appears that a water surface of approximately 600 acres will be opened up over a seven year period. This additional surface does not appear to be a part of the anticipated 1150 acre recreational pool and the additional evaporation loss does not appear to be accounted for in the projected evaporation loss of 2500 acre-feet per year from said recreational pool. In short, it seems the additional gravel removal operation in the upper reaches of the perma nent pool has the potential for damaging downstream water users through increased evaporation loss at least in the amount of 13 00 acre-feet per year. This amount of consumptive use could be very damaging in dry years and I feel the project should be prepared to make replacement for such lo sses. I look forward to receiving your comments concerning this issu e. Very truly yours, cc: W. G. Wilkinson C . / . Kuiper T. W. Ten Eyck State Engineer JOHN D. VANDEKHOOF Govufnnr DEPARTMENT OF NATURAL RESOURCES COLORADO WATER CONSERVATION BOARD 102 COLUMBINE BUILDING 1845 SHERMAN STREET DENVER, COLORADO 80203 Way 28, 1974 Colonel Russell A. Glenn District Engineer Omaha District, Corps of Engineers 6014 U. S. Post Office & Court House 215 North 17th Street Omaha, Nebraska 60102 Dear Colonel Glenn: This board has reviewed your recent publication entitled "South Platte - Chatfield Dam to Denver, Alternatives." Represen tatives of the board have also attended the various public meetings held in connection with this report. The state of Colorado, through the Colorado Water Conser vation Board, has previously agreed to act as the sponsoring agency for the improvement of the South Platte channel below the Chatfield Dam, and has executed an agreement with the United States to this effect. We had anticipated that channel consutruction would be under way by this time and we are greatly concerned abou.t the long delay in getting the channel improvement under way. In connection with that, stretch of the river from Chatfield Dam to Coal .Mine Road, we have previously endorsed and continue to endorse your alternative Mo. 2 which is described as the Littleton Plan. We have already furnished funds to the city of Littleton to complete this plan. This is the sole and only alternative which has been endorsed by the membership of this board. In connection with that stretch of the river from Coal Wine Road to West Hampden Avenue, this board endorses your alternative No. 4 'which provides for channel enlargement to accommodate an into me d i a t o regional flood.. No other course of action listed in your report is ' acceptable to this board. We have previously considered the various alternatives and it is our opinion that the protection of life and property through the Denver metropolitan area requires the channel enlargement which has already been planned, We therefore request that construction of this enlargement be initiated as speedily as possible, and we arc prepared to furnish the necessary lands, rights-of-way and easements. We do request, however, that this channel enlargement be coordinated with the plans of the city of Englewood to construct a public golf course along that section of the river lying generally between Oxford Avenue and Ilampden Avenue. Very truly yours, *' FELIX L. SPARKS Director United States Department ol the Interior OFFICE OF THE SECRETARY MISSOURI BASIN REGION BUILDING 67. DENVER FEDERAL CENTER DENVER. COLORADO 80275 KSY 3 0 fjft Hr. C. F. Thomas Chief, Planning Division Department of the Army Omaha District, Corps of Engineers 6014 U.S. Post Office and Court House Omaha, llebraska 68102 Dear Mr. Thomas: This responds to your letter of April 12, 1974, requesting review and comments on the Draft Environmental Statement, Chatfield Lake, Colorado. The attached comments are a composite of those made by the field offices of the various Department of the Interior agencies. Sincerely yours, , Special Assistant , to the Secretary^ Comments on Draft Environmental Statement Chatfield Lake, Colorado (ER-74/507) General Comments 1. Even though this draft statement conforms to CEQ Guidelines in format, it does not discuss specific impacts or losses in quantifiable terms. Perhaps the most serious problem that is recognized is the severe erosion of downstream portions of the channel resulting from releases following flooding conditions (pages 3-8). The mitigative measures to reduce this impact should be an integral portion of the statement and not addressed in a "downstream channel environmental statement supplement". The alternatives currently being considered (pages 5-9) appear to be of greater magnitude than the construction of the Chatfield Dam. In addition, the original project authorization (Flood Control Act of 1950) provided for "flood protection along portions of the South Platte River from the dam (Chatfield) downstream to Fort Morgan". What measures are contemplated between West Hampden Avenue and Fort Morgan? 2. Pertinent portions of the referred to "Master Plan for Chatfield Lake" and the "vegetative management plan" should be also incor porated in the statement. 3. Mo established or studied units of the National Park System appear to be adversely affected by the proposal. 4. The proposal does not appear to adversely affect any site registered as a National Historic, Natural or Environmental Education Land mark, or any site listed as eligible for such registration. 5. The statement does not reflect that the National Register of Historic Places has been consulted. The final statement should reflect consultation with the Federal Register for February 19, 1974, which is a composite list of National Register sites up to that date and all subsequent monthly supplements. Supplementary listings of sites added to the National Register, subsequent to publication of the previous supplement, are cited in the Federal Register appearing on the first Tuesday of each month. The state ment should also establish whether a proposed project will have an effect upon a National Register listing. Where this is found to be the case, the procedures relating to compliance with Section 106 of the National Historic Preservation Act of 1966 (P.L. 89-665) and Executive Order 11593 become operative. 6. The statement does discuss archeological, historical, and paleontological surveys made some years ago. It should indicate what further surveys are contemplated in advance of activities which irretrievably commit resources to implement the Chatfield Lake project. There have been advances made in the techniques used to study lands possessing potential cultural resources. The statement should also indicate what action will be taken to salvage any significant remains found once the project is started. 7. Discussion of the cultural resources in the Chatfield Reservoir area (p. 2-15, 2-16) is both inadequate and inaccurate. Withers' 1972 report should be used in correcting the information: (1) Survey and excavation by the University of Denver was done during the middle 1960's, not during the late 1940's. (2) Many unexcavated sites remain, although their significance is such that full scale excavation may be unwarranted. However, Withers (1972: 3-5) makes specific recommendations for further testing and excavation of Colorado: K:8:50, Colorado: K:12:14, Colorado: K:8:41, Colorado: K:3:66, Colorado: K:8:52, Colorado: K:8:53, Colorado: K:8:54, Colorado: K:8:56, Colorado: K:8:60. (3) No excavation, other than limited testing, has been carried out in the reservoir area. The statement does not discuss potential impact on the cultural remains; no mitigating measures are recommended, nor are any irreversible and irretrievable commitments of the resources recognized. Withers (1972: 2) specifically states that all 31 sites located within and adjacent to the project boundaries will "either be inundated or endangered by construction, highway relocation, or people using the recreational facilities." 8. In regard to the National Register nomination, there is no indication that the "Criteria for Effect," established by the Advisory Council on Historic Preservation, has been applied to the Hildebrand Ranch. This is required under Section 2b, Executive Order 11593. If any possible adverse effect is found, such as inundation at the maximum flood pool level 5500', or as a result of increased recreational use of the area, Advisory Council consultation must be effected. 9. To be complete, the statement should: (1) provide an inventory of the sites within the project area, (2) assess their significance in terms of the archeology of the general region, (3) note the adverse impact on the nonrenewable remains, (4) discuss mitigating measures that would be or have already been implemented (results of this work, such as Wedel's 1961-64 excavations at the Lamb Site (Colorado: K:8:49) should be detailed), (5) demonstrate effective communication with the State Historic Preservation Officer, and (6) detail application of the "Criteria of Effect" to the Hildebrand Ranch. 10. The Bureau of Mines primarily is concerned with the effect of the Chatfield Dam and Lake on the recovery of mineral resources in the project area. A study of mineral resource involvement at the site was completed by the Bureau of Mines in 1966. It con cluded that large quantities of sand and gravel would be irre trievably committed if an extraction plan was not formulated. The draft environmental statement does not refer to this Bureau of Mines resource study, but it does mention a sand and gravel extraction plan based on a study by the University of Illinois (page 2-15). neither the University of Illinois study, nor the gravel extraction plan, is appended to the draft environmental statement. Data contained in the statement and illustrated in Plate 5 indicate that, although considerable quantities of sand and gravel will be rendered unrecoverable, the present plans will provide for substantial recovery of this resource. Unrecovered resources are discussed on page 3-9 of the draft environmental statement, where it is correctly stated that, "Any gravel that remains after the pool fills will not be available for use in the future." However, there is no mention of such an adverse environmental effect on page 4-1, Section IV, Adverse Environmental Effects Which Cannot Be Avoided Should the Project Be'Implemented. Ho mention of the long-term effect of unrecovered sand and gravel on metropolitan growth is included in Section VI, Local Short-Term Uses of Man's Environment Versus the Maintenance and Enhancement of Long-Term Productivity; and there is no mention of the irretrievable loss of this unextracted resource in Section VII, Irreversible and Irretrievable Commitment of Resources Which Would be Involved in the Proposed Action Should It Be Implemented. The draft environmental statement is generally thorough and well written, making excellent use of graphics in the series of illustrations at the end of the report. We believe the compre hensiveness and utility of the report would be enhanced by appending to it the 1966 Bureau of Mines resource study, the referenced University of Illinois study, and the "gravel extrac tion plan." We recommend the addition of appropriate paragraphs to sections IV, VI, and VII, dealing with the sand and gravel which will not be recoverable owing to inundation, location in the river channel, or for environmental or aesthetic reasons. 11. The statement does not discuss in detail the off-site impacts caused by construction. How many miles of access roads, powerlines, pipelines, equipment storage areas, and cubic yards of fill material are required. Where will solid and liquid wastes from construc tion of the site be disposed? What are the impacts of these waste materials, which could include toxic chemicals, gas, and oil, upon the soil and water? • 12. This report was well presented and very clear-cut in its read ability. The main problem that we can see is that the entire statement is "after the fact." Thus, many areas in the report are approached on the assumption that the work is already com pleted, therefore, further explanation is not needed. Specific Comments 1. Pages 1-9. Gravel extraction does not seem congruent with the proposed heavy use recreation area nearby. There have, though, been extensive landscape, pond shape, and mining restrictions designed for this project (restrictions, 3-18). The nine resulting ponds will be in the flood plain and during high flows would be inundated. This will result in rapid siltation of the ponds resulting in a loss of their usefulness as fishing areas. They would remain as marshes suitable for wildlife habitat. Gravel mining restrictions and mitigation of damage must be strictly adhered to and a strengthening of these restrictions would better protect recreation interest, if the gravel must be mined. 2. Pages 2-17. This report fails to dwell on the amount of water that will be available for use and reserve pending the projected increase in development along the site. What exactly are the projections for the water reserve utilization and surplus in regard to further development? A growth plan was proposed, but water resource, which is second only to flood control in this project, was not given proper attention. Will the ultimate growth projection ci'eate a problem insofar as availability of treatment and disposal of wastes? If so, definitive plans for growth and buildup should be outlined so that an impact on the area will be known. 3. Page 2-20, Last Paragraph - Phosphates (P0it): The reference to Public Health Standards for phosphates should be expanded to indicate which Public Health Standards you have used. We are unaware of any Public Health Standards for phosphates. 4. Page 3-4, Paragraph 3: There appears to be some discrepancy among the reasons that the lake will not become stratified. (1) Dimictic lakes stratify at least twice per year. (2) Cool inflowing waters will sink to a layer of equal density, which would stabilize existing thermal stratification. 5. Pages 3-6. The most urgent wildlife concern is for the heron rookery which will be flooded by normal pool level. Numerous species of birds and other animals also live here. Therefore, any possible alternative cottonwood nesting areas upstream should not be cut or cleared. The planted cottonwood grove 300 yards upstream may not be large enough to take care of the animal migration. No gravel should be mined nearby. The present 900 foot buffer area around the rookery does not seem large enough considering the noise and disturbance caused by the heavy machinery used in gravel excavation. 6. Pages 3-10. Under "Loss of Agricultural Production,” second paragraph: Air pollution and fuel consumption are necessary secondary effects to finish the lake and dam site. They should, however, be given more than a passing thought in regard to their effects on the area and possible damage now and in the future by the proposed increased usage. 7. Page 3-16, Paragraph 1: It is stated that the water quality of the South Platte River is sufficiently high that nuisance algal blooms will not occur. If this is true, then adverse effects from thermal stratification should not occur and destratification, if it can be accomplished on a lake of that size, would be unnecessary. Destratification for the purpose of preventing hypolimnetic anoxia may cause an increase in primary production due to the introduction of nutrient rich bottom waters or increase turbidity by bringing up the bottom waters, which would be higher in suspended solids. An increase in the annual heat budget could also be expected; this would change the downstream fauna. Aeration of the anoxic hypolimnion would seem a better alternative should any measures need to be taken. 8. Page 5-1 - Alternatives to the Proposed Action. The alternative of increasing the height of Chatfield Dam to provide storage for Denver's municipal and industrial water, thus eliminating the need for Two Forks Dam is not discussed. Other alternatives which could still be implemented include the reallocation of Chatfield storage to municipal and industrial storage and the construction of a flood control structure on Plum Creek. These alternatives would eliminate the environmental damage associated with construction of the Bureau of Reclamation Two Forks Reservoir while accomplishing the purposes of flood control and municipal and industrial storage. These alternatives should be discussed in detail in the final environmental statement. DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT FEDERAL BUILDING, I 9th AND STOUT STREETS DENVER, COLORADO 80202 May 30, 197^ Mr. C'. F. Thomas Chief, Planning Division Department of the Army Omaha District, Corps of Engineers 601^ U. S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: ..We have reviewed the Draft Environmental Impact Statement on Chatfield Lake on the South Platte River just south of the Denver Metro area. We believe the statement to be well prepared and satisfactory for the purposes of evaluation by this Department. We recommend completion of the project as proposed. The flood control aspect of the project will offer needed protection of a considerable area of Metro Denver. As you may know, some portions of areas under Urban Renewal treatment were affected by the 1965 flood, which will now receive additional protection. The Jerome Park, Colo. R-8, and Auraria Project, Colo. R-2U, in particular, will benefit. In addition, HUD funded a study of redevelopment along the Platte River in Denver at a cost of $280,000 as a result of the disastrous flood. The construction of the Chatfield Dam will make a major contribution in the implementation cf the recommendations of this study. We are also in agreement with the extensive recreational facility proposals in conjunction with the project. Water and water related recreational activities are relatively scarce or crowded in the Denver Metro area. Nearby opportunities for outdoor activities as will be provided will undoubtedly make an important contribution to the environment of the urban area. Thank you for the opportunity to comment on the Chatfield Lake. . Sincerely, Lee R. Euttrill Director, Community Evaluation and Standards Division Community Planning and Management Colorado John D. Vanderhoof / Governor Division of Planning 1575 Sherman Street / Denver, Colorado / 80203 Department of Local Affairs Philip H. Schmuck / Director Phone / (303) 892-2178 May 30, 1974 M r. C. F. Thomas Chief, Planning Division Department of the Arm y Omaha District, Corps of Engineers 6014 U. S, Post Office and Court House Omaha, Nebraska 68102 SUBJECT: Colorado State Clearinghouse Comments on Draft Environmental Statement for Chatfield Lake, Colorado Dear M r. Thomas: The Colorado State Clearinghouse has reviewed the Draft Environmental Statement (DES) for Chatfield Lake. The DES is adequate in most respects, but some very critical concerns are not addressed. The matters discussed below should be assessed in the final environmental statement. 1 . The relationship of the Chatfield Dam to the Bureau of Reclamation’s proposed Two Forks Dam and Reservoir (2-4) * must be more thoroughly assessed. Arm y Corps of Engineers guidelines, para graph 7a(7)(a), require that "significant relationships between the proposal and other existing and anticipated developments" be dis cussed, including "not only corps proposals but actions by others, either public or private, which may be affected by the project." 2 . An assessment of alternatives concerning the downstream floodplain should be part of the DES as the "Chatfield project" (1-2) includes the area between the dam and Hampden Avenue. The floodplain alternatives cannot be assessed independently of the dam. * All page references are to Draft Environmental Statement, Chatfield Lake, Colorado, unless otherwise noted. Department of the Arm y Omaha District, Corps of Engineers Chatfield Lake DES Page 2 a . The Clearinghouse supports the alternative proposed by the City of Littleton (1-2) as it would be contributing to the multipurpose benefits and uses of the Chatfield dam. The Littleton proposal would also preserve immeasurably valuable linear open space, a form of open space that is most efficient in terms of accessi bility and visual impact. b . An assessment of downstream floodplain alternatives is essential, particularly if "there would be an ultimate loss of downstream open space, wildlife, and wildlife cover, heretofore protected by the periodic flooding of the South Platte River" (3-9). While it is true that "local authorities" (3-9) must ultimately control land use in the area, it is important for the Corps of Engineers to take action on the downstream floodplain because one of the detrimental consequences of the Chatfield dam and lake w ill be increased "pressures for urbanization" (3-9). One way to mitigate this detrimental effect would be to acquire the floodplain downstream to prevent the encroachment that could ultimately defeat the main purpose of the dam. 3 . The secondary, or indirect, consequences of the Chatfield dam and lake must be assessed,. a . Guidelines issued by the Council on Environmental Quality (CEQ) stipulate that secondary effects stimulated by a project, such as "associated investments and changed patterns of social and economic activities" should be included in an environmental impact analysis (38 FR 20553). b . The impact of the Chatfield dam and lake on "land use, water, and public services of the area in question" (CEQ guidelines paragraph 1500.8, 38 FR 20053) must be assessed. 4 . The impact of the dam and lake on the Hildebrand Ranch is not assessed. The discussion referred to on page 2 -1 6 does not take place. The Corps of Engineers should notify the Advisory Council on Historic Preservation as required by the Historic Preservation Act of 1966 and Executive Order 11593 regarding measures to be taken to protect the Hildebrand Ranch and other historical and cultural resources affected by the dam and lake. Department of the Arm y Omaha District, Corps of Engineers Chatfield Lake DES Page 3 5 . The impact of the dam could be better assessed if the DES were more s p e c ific . a . How were the benefits "assigned" (3-2) to the dam project actually determined? b . The "vegetative management plan" (3-12) should be appended to the DES. c . Where is the mining for the riprap taking place? (3-10). Are any measures being taken to mitigate the impact of this mining? d . Who are the "experts" (3-16) anticipating that the herons will move to the new nesting area? e . W ill 900 feet be an adequate distance to buffer the heron nesting activities from the gravel mining operations? The Clearinghouse supports the multipurpose concept that the Corps of Engineers has used to select the alternative that was chosen. We would urge the Corps to extend this concept to the downstream area included in the entire project. We would like to commend Omaha District Office of the Corps for working in close cooperation with local residents and with local and State agencies. The Clearinghouse review of the DES was hampered somewhat by the irregular distribution of the DES to State agencies. Future environmental statements can be better assessed by the Clearinghouse if the Omaha District of the Corps would utilize the Clearinghouse to distribute the statements to State and local agencies, and I would like to request that your office help us in this regard. I hope that these comments w ill be helpful in preparing a final environmental impact statement. Please contact me if the Clearinghouse can be of help. S in c e re ly , Philip l-f. Schmuck D ir e c to r cc: John Bermingham, Assistant to the Governor on Environmental Affairs and State Planning J. D. Arehart, Executive Director, Department of Local Affairs Jack Grieb, Director, Division of Wildlife W. E. Marshall, Executive Director, State Historical Society B. Thomas Lofft, Director of Community Development, City of Littleton Lou W all, Assistant Director, Office of Compliance, Advisory Council on Historic Preservation George T . O'Malley, Director, Division of Parks and Outdoor Recreation Frank Rozich, Director, Water Quality Control Division Robert D. Farley, Executive Director, Denver Regional Council of Govts. M. D. Burdick, State Conservationist U n i t e d S t a t e s D e p a r t m e n t o f A g r ic u l t u r e FOREST SERVICE Rocky Mountain Region Building 85, Denver Federal Center Denver, Colorado 80225 May 31, 1974 Mr. C. F. Thomas Chief, Planning Division Department of the Army Omaha District, Corps of Engineers 6014 U. S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: Thank you for the opportunity to review the Draft Environmental State ment for the Chatfield Lake, Colorado. Our comments are: I. Page 1-8: In the last paragraph, please change ". . . Forestry Department" to ". . . Forest Service. ..." Page 1-10: The $1,500,000 non-Federal cost does not include the $3,000,000 budgeted by the State of Colorado to fill the multi-purpose pool and replace evaporation losses. This needed investment is directly related to recreation benefits. II. Page 2-3: The effect of the Bear Creek Mountain-Carbon Project on South Platte River floods and the size of the multi-purpose pool and recreation use capacity that could be maintained should be analyzed. Page 2-13: Only consumptive recreation uses are discussed. At least equally important to consider are such things as birdwatching, walking, sport shooting, etc. III. Page 3-2: The provision of significant recreation oppor tunities so close to an urban area has favorable effects from both energy consumption and accessibility for the economically disadvantaged standpoints. Page 3-12, first paragraph: Please replace the last sentence with "The Forester referred to is the Regional Forester, Rocky Mountain Region of the USDA - Forest Service, or his designated representative." V. Page 5-7,8: The Statement refers to "high sustained flows" from flood pool evacuation from the lake with severe downstream bank erosion and other adversities probably occurring. Cannot this operating principle be modified to protect downstream habitat? If not, could project funds be used to armor the more sensitive locations? Generally, we feel the Statement could be strengthened by additional information relating to recreation planning for the general area as affected by this project. B. K. CRANE Deputy, Resources CITY AND COUNTY OF DENVER DEPARTMENT OF PLANNING OFFICE OF DIRECTOR ROOM 300 1445 CLEVELAND PLACE DENVER, COLORADO 80202 June 13, 1974 Department of the Army Omaha District, Corps of Engineers Omaha, Nebraska 68102 RE: Chatfield Lake Draft Environ mental Impact Statement Dear Sirs: Thank you for providing the City and County of Denver with an opportunity to review the Chatfield Lake Draft Environmental Impact Statement. Our review has generated the following com ments : 1. Of special importance to the City and County of Denver are the statements made on pages 5-7, 5-8, and 5-9. These state ments call attention to the fact that the routine operation of Chatfield Dam can produce flooding between the dam and Denver. The statement on these pages also indicates that not only is localized flooding possible, but because the water will be essentially sediment-free when it leaves the reservoir it will be more capable of picking up sediment as it moves downstream. This combination of high sustained flows and the capability to pick up and transport sediments can lead to erosion problems possibly greater than we have experienced in the past. This impact statement does explain that a supple mental impact statement will address these problems. It is therefore suggested that Denver be given an early opportunity to monitor the development of that supplemental impact state ment. 2. Because of the above-mentioned possibility of floods below the dam associated with routine operations, we request that as a part of the Final Environmental Impact Statement that up to date 100-year and standard project flood outlines and profiles be prepared that will in detail describe the flood threat be low the dam until such time as channel improvements, if any, are performed In the reach between the dam and Denver. Sincerely yours, Alan L. Canter Director of Planning cc: Harold Cook E. W. Lewan II. L. Smith UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION VIH I860 LINCOLN STREET DENVER. COLORADO 60203 JUl 1 S 1374 Mr. C.F. Thomas Chief, Planning Division Omaha District, Corps of Engineers 6014 U.S. Post Office and Court House Omaha, Nebraska 68102 Dear Mr. Thomas: The Environmental Protection Agency has reviewed the draft environmental impact statement for Chatfield Lake, Colorado and offers the following comments for your consideration. Our comments relate primarily to the secondary and the water quality impacts of this project. As you know, the secondary impacts from Federal actions such as the funding of a highway, the funding of a sewage treatment plant, the building of a reservoir or the issuance of a permit for ski area development may be more environmentally degrading than identifiable primary impacts. Secondary impacts are difficult for Federal agencies to deal with, not only because these impacts are difficult to analyze and describe, but more importantly because die prevention or mitigation of these impacts requires close coordination with State and local governments which have the police power authority to control land use decisions on non-Federal lands. In dealing with secondary impacts, Federal agencies have two equally important responsibilities: 1. To adequately predict, analyze and describe the secondary impacts of the proposed Federal action; and 2. To implement preventive and mitigating measures to control secondary impacts through the use of Federal authorities and through close coordination with State and local governments. Coordination with local governments to control secondary impacts depends on such factors as the attitudes of local officials, the adequacy of local land use plans, and the adequacy of local land use control ordinances and regulations. In some instances, Federal actions may have to be delayed until local governments develop the necessary plans and controls. Such delays can be avoided if there is early and continuing coordination and cooperation between Federal and non-Federal entities throughout the planning process. We recognize that a great deal of coordination has taken place between your agency and State and Local governments concerning the Chatfield project. However the EIS does not indicate whether this intergovernmental coordination addressed the secondary impacts of the project on population growth, land use, utility services and environmental degradation in the drainage area above the dam. Our review of this EIS indicates the following: 1. The analysis and descriptions of secondary impacts must be expanded to present a general overview of such impacts on the drainage area above the dam. 2. The EIS should analyze the adequacy of Federal, State and local legal authorities and plans presently available to control secondary impacts. The EIS should detail the governmental actions which must be taken to adequately prevent and control adverse secondary impacts. Enclosed is a recent draft EIS on proposed v/astev/ater treatment facilities in the Southwest Denver Metropolitan Area which may be a useful reference concerning this secondary impact discussion. We noticed that the EIS on pages 2-21 and 3-7 acknowledges the potential non-point water quality impacts resulting from urban development in the drainage above the dam. The EIS would be improved if there were a brief, general discussion of the preventive and mitigating measures that might be utilized by governmental agencies in the long run to control this non-point impact. Certainly local governments bear an important responsibility to control this impact through their land use planning and regulatory authorities. You might also mention the possibility that these non point water quality impacts could be addressed in a water quality management plan prepared pursuant to section 208 of the Federal Water Pollution Control Act, as amended. You might also mention the Corps responsibility under section 209 of that same Act. You might want to consult with EPA, the State of Colorado and the Denver Regional Council of Governments concerning the possibility of studying the non-point problems around Chatfield Lake as part of any future section 203 water quality management plan. The discussion on page 3-7 of the EIS concerning the water quality impacts of reservoir operation should be expanded. Where and how will the State of Colorado obtain the water supply necessary to replenish the pool to elevation 5426 feet m.s.l., and also supply any water guaranteed to downstream users? How will the reservoir be operated if Colorado cannot for some reason replenish the pool to elevation 5426 feet m.s.l.? What flow will be released under this circumstance? Is there data quantification to support the statement on page 3-7 which says: "However, it is anticipated that such occurences will be infrequent and will not create conditions significantly worse than what has historically occurred during extended periods of low flow"? i Your supplemental environmental impact statement dealing with the South Platte between Chatfield Dam and West Hampden Avenue should discuss the impact of various alternatives on waste water treatment facilities and interceptor sewers in the area. Based on the rating system that EPA has developed for rating the environmental impact statements of other Federal agencies, this EIS is given a rating of LO-2. A copy of this rating system is enclosed for your information. Please send us a copy of the final statement. Sincerely yoursy n A. Green Regional Administrator CHAPTER 3 ■ PREPARATION, APPROVAL, AMD DIHTKI.'iUTION OF COMMENTS ON’ REVIEW OF FEDERAL ACTION’S ENVIRONMENTAL IMPACT STATEMENTS IMPACTING TIiK ENVIRONMENT Environmental Impact of the Action LO—Lack of Objections EPA has no objections to the proposed action as described in the draft impact statement; or suggests only minor changes in the proposed action. ER—Environmental Reservations EPA lias reservations concerning the environmental effects of certain aspects of the proposed action. EPA believes that further study of suggested alternatives or modifications is required and has asked the originating Federal agency to reassess these aspects. EU—Environmentally Unsatisfactory EPA believes that the proposed action is unsatisfactory because of its potentially harmful effect on the environment. Furthermore, the Agency believes that the potential safe guards which might be utilized may not adequately protect the environment from hazards arising from this action. The Agency recommends that alternatives to the action be analyzed further (including the possibility of no action at all). Adequacy of the Impact Statement Category 1— Adequate The draft impact statement adequately sets forth the environmental impact of the proposed project or action as well as alternatives reasonably available to the project or action. ‘ Category 2— Insufficient Information EPA believes that the draft impact statement does not contain sufficient information to assess fully the environmental impact of the proposed project or action. However, from the information submitted, the Agency is able to make a preliminary determination of the impact on the environment. EPA has requested that the originator provide the informa tion that was not included in the draft statement. Category 3— Inadequate EPA believes that the draft impact statement does not adequately assess the environmental impact of the proposed project or action, or that the statement inadequately analyzes reasonably available alternatives. The Agency has requested more information and analysis concerning the potential environmental hazards and has asked that substan tial revision be made to the impact statement. If a draft impact statement in assigned a Category 3, no rating will be made of the project or action, since a basis does riot generally exist cn which to make such a determination. The Wilderness Society i JuO L. i.v.Hc Avi'inii', I Vmrf, ( kIih.kIo !{i)l2L!2 Wr'.irrn Kf;:i<>n;il (111i«"»* riiotio (30.i) 7."i}! 22(t(i May 3, 1974 Mr. C. F. Thomas Chief, Planning Division Omaha District, Corps of Engineers 6014 U.S. Post Office and Court House Omaha, Nebraska 68102 Subject: Draft Environmental Statement for the Chatfield Lake, Colorado project. Dear Mr. Thomas: The Wilderness Society is concerned that every opportunity be taken to preserve natural areas near population centers, even though these areas may not qualify for wilderness classification, because these resources provide close-in opportunities for recreational use and reduce recreational use of more distant and more pristine areas. The draft statement indicates careful consideration to the enhancement and preservation of natural areas, and response to previously expressed public opinion. It is suggested that the "open" sector for water use be relocated to the eastern third of the reservoir. The presently planned location between the "motorlcss" and "wakeless" sectors has two major drawbacks. There are two water boundaries to enforce for the open sector, and the visual, audible and wave influence of the open sector will affect practically all the shoreline. Locating the open sector in the eastern arm would affect the least amount of semi-natural shoreline, dam construction could provide for minimal effect of wake generated by wave action, and the expected major boundary enforcement problem (high power boats, water skiing vs. low powered or motorless boats, fishing) would bo reduced by half. Please send The Wilderness Society a copy of the downstream channel draft environmental statement supplement when it is distributed. Sincerely yours, William B. Mounsey Wilderness Consultant metro5"1* denver league of women voters 28 May 197^ C.w . Thomas Chief, Planning Division Omaha District, Corps of Engineers 601*1 U.S. Post Office and Court House Omaha, Nebraska 6^102 Dear Hr. Thomas; The League of Women Voters of Metro Denver thanks you for the ooportunity to comment on the Draft Environmental Statement for the Chatfield Lake, Colorado, project. We are particularly concerned about the connection between the presently planned highways, for example I-k.7 0 , and the facilities to be constructed at Chatfield Lake. Are projected users of the recreational facilities dependent on 1-^70 a 6 lar.e highway? Certainly the Joint Regional Planning Program naps should be included in the Environmental Impact Statement. Alternative forms of transportaion which would decrease the impact on the area need to be explored. Also, we believe it is important to know the effect on air quality by visitors to the Lake. It would appear most advis able to do a complete environmental assessment•of a larger area. We need to be able to assess the overall impact on such an area. Careful consideration must be given to using Chatfield Lake as a source of Municipal and Industrial water. Therefore, fail to see the wisdom of continuing a recreational project which may have to be abandoned or destroyed due to incorporation of such changes, ^uthernore, an overall viewpoint of the possible connection between Two ^orks or its equiva lent, if developed, and Chatfield Lake appears to be essential. The League of Women Voters believes that lone: range ecological values are to be placed above short term solutions. With this in view, we believe it is essential to explore maintaining a relatively natural setting at Chatfield Lake. The Lake will be a sanctuary for birds and water animals and could be left to these animals. Motor boats could be keut out and other vehicles kept an far from the lake as possible. In all events the quality of the v/ator must be preserved. Thank you again for the opportur.ity to comment. Sincerely yours, Ifarg Ann Part on, President Toni '.'/orcester, Comprehensive Coordinal 869 Milwaukee Street Denver, Colorado 80206 District Engineer U. S. Array Corps of Engineers Omaha District '6014 U. S. Post Office and Courthouse Omaha, Nebraska 68102 Attention: Mr. Jack Dover Gentlemen: Re: Draft Environmental Statement Chatfield Lake, Colorado This letter is submitted as a comment on the draft environmental statement on Chatfield Lake. The scope is so limited that it does not consider the environmental changes which have already occurred due to the construction project, nor those which will occur after completion of the construc tion. To identify myself, I am one of the two leaders in the study referred to on Pages 2-11 et seq. and I compiled the bird study attached to the statement as Appendix A. All of these studies have been contributed to the Corps of Engineers gratis, as a public service and as an appreciation of the an nounced plans to preserve the Green Ribbon of the Platte as a wildlife preserve.- Flora: The grove of large cottonwood trees referred to on Page 2-7 is the remnant of a much, larger grove which ex tended along the entire stream bottom. In planning the project, the Corps cut all the trees along the stream, within the perman ent pool, except for this grove. I commend the Corps, having made the decision to remove all the trees within the permanent pool, for having decided to preserve this grove because it held a Great Blue Heron heronry. V7e also appreciate the opportunity which the Corps has extended us for permitting the study of the grove as changes occurred, due to the project. Birdlife: The discussion of birdlife on pages 2-11 et seq. is a bit jumbled, with a confusion between the birds in the heron grove and those along the rest of the river. Some of the discussion is limited to the first year's study of the heron grove rather than the full three and one-half year study conducted so far. Most of these comments, however, refer to minor errors ^rather than major mistakes. For example: Scrub Jays do not nest within the project area at all, although they do nest in the foothill scrub habitat immediately west of Waterton. Screech Owls do not nest within the heron grove, although they no doubt do nest in other cottonwood sites upstream from the grove (Page 2-12). The breeding birds listed in the last paragraph on Page 2-12 are those found in the heron grove, and represent only the 1971 study. The list is slightly misleading because outside the heron grove, the Great Blue Heron does not nest. The first paragraph on Page 2-13 mixes observations from the flood plain (40 nesting species) with those of the grove (mid dle of paragraph). Appendix A, which I prepared with itdput from other members of the Denver Field Ornithologists who have also made observations in the area, is truncated unfortunately by the omission of graphs which show the frequency of occurrence of the species. Deletion of this graph substantially diminishes the worth of the Appendix. It certainly embarrasses me because of its incompleteness. I strongly request that you return the graph to the Appendix in order to make it whole. I will be glad to redraft the birdlife section of the report to make it accurate (but not before July 15). Gravel Resources: We have observed an occurrence this Spring which the environmental impact discussion does not contem plate, and indeed which none of the discussions on Chatfieid which I have heard have contemplated. On the west side of the grove approximately 75 trees have died since last year. These trees lie very close to the site of gravel mining which has continued for the past two years. Part of the mining observation has required pumping the water out to facil itate extraction of the gravel. On preliminary observation we be lieve that the pumping has so lowered the water table that the trees have been unable to survive. • In the Winter or Spring of 1974 another gravel operation has rechannelod the Platte to the far east portion of the flood plain to facilitate gravel mining on the north and east sides of the heron grove. We speculate that the rechannelization may have a similar effect upon the east-side trees — which include those in which the herons nest. It seems possible, based on the results * from the mining on the west side, that the heron trees may die P r e maturely, thus forcing an early end to the heronry. These comments are based only on observations from the past three weeks, since the leaves came out on the trees, and we have no environmental studies to document the cause of the death of the trees. However, the proximity of the dead trees to the earliest gravel mining indicates a danger point which should govern plans if they are to succeed in preserving the heronry. Much of the discussion of mitigating circumstances an ticipates a relocation by the herons to a newly planted grove. If the present grove dies prematurely because of the gravel mining, the heronry may break up before the new grove readies itself for receiving the herons. Of course, if sufficient protection is given to the upstream cottonwood habitat (i.e., protection from human disturbance), then the herons would have the existing flood plain trees as an alternative heronry site. Thanks for the opportunity of making these comments. Yours truly, / / V > K. ' ^ . / t - 'Hugh'E. Kingery" cc: Mr. Jack Kepler Corps of Engineers 6014 U. S. Post Office and Courthouse Omaha, Nebraska 68102 District Engineer U. S. Army Engineer District, Omaha 6014 U. S. Postoffice and Court House- 215 North 17th Street Omaha, Nebraska 68102 Dear Sir: We are pleased to note that the completion of the Chatfield Dam is proceeding ‘on schedule, and we are proud of the vital part our Committee has had in its formulation. We are concerned, however, with the year by year delay in channelization of the South Platte River /rom the dam north to.the city limits of Denver. Channelization of this part of the river is a vital part of the entire project and until its completion as planned, protection from flooding re mains unfulfilled. It has recently come to the attention of our Committee that .the U. S. Corps of Engineers has bee", authorized, but not mandated, by Congress to release to the City of Littleton the sum of approximately~¥600,000, the estimated cost of channelizing the two miles of river below the dam to the Town of Columbine Valley. It is also our understanding that these monies alcng with donations from other Federal agencies such as KUD and the Bureau of Outdoor Recreation are planned to be used by Littleton to purchase private floodplain lands in order to let'the river run wild and flood these lands in time of heavy rains or release of water from the dam. The Dam the Platte Committee represents citizens and communities who suffered great damage by the disastrous flood of June 16, 1965. We were the most influential group in promoting the Chatfield Project and insuring its con struction. , The whole purpose of the Chatfield Project is protection from floods. We have always concurred with the opinion of the U. S. ..Corps of Engineers that both construction of the Dam and channelization downstream are essential in order to meet the intent of Congress and the downstream communities -- flood protection. We are not only interested in flood protection. We are also interested in a beautiful river that is characterized by low cost upkeep. If a part of the river is left unchannelized, downstream portions will receive silt and trash from’the unprotected area, just as we did in the 1965 flood. This will mean raising taxes by each community to keep the channel clean. We remind you that your obligation'and duty is to engineer a complete Chatfield Project which will eliminate flooding of the South Platte River from the Chatfield Dam tp the.city limits of Denver. As near as possible this should be an engineered project which will result in an essentially maintenance-free river. We also remind you that whatever the political pressures, authorization from Congress is far different than a mandate. Our Committee wishes to go on record that to leave a portion of the South Platte River unprotected from flooding and future maintenance costs uncontrolled will subvert the intent of Congress and renig on the promises you have made to our Committee and the thousands of people we represent. We believe that it is time that complete channelization be commenced at an early date. Sincerely yours, DAM THE PLATTE COMMITTEE Jack Shapiro, President