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* ,:-, - , . , n ~ t , . D - o o' o= .. p- w j s , FEBRUARY 09, 1981 Y b

m .. '' El N Docket No. 50-29 ' LS05-81-02-013 - p P: us y - . ,y , -

x- ,a. .. . i.;. ' Mr. James A. Kay @i 3 ; Senior Engineer - Licensing m Q@S '" E Yankee Atomic Electric Company 71 # 1671 Worcester Street G L'd Framingham, Mass. 01701 Dear Mr. Kay:

SUBJECT: TOPIC II-3.A. HYDROLOGIC DESCRIPTION AND TOPIC II-3.B. (FARTIKL),FLOODINGPOTENTIALANDPROTECTIONREC,UIREMENTS (YANKEER0WE) / Enclosed is a copy of our draft evaluation of Systematic Evaluation Program Topics II-3.A and 11-3.B. You are requested to examine the facts upon which the staff has based its evaluation and respond either by confirming that the facts are correct, or by identifying errors and supplying the corrected information. We encourage you to supply any other material that might affect the staff's evaluation of these topics or be significant in the integrated assessment of your facility. Your conclusions regarding the subject topics and your seismic evaluation - of the dam should be considered together because of possible interrelationships between the subjects.

Your response is requested within 30 days of receipt of this letter. If no response is received within that time, we will assume that you have no consnents or corrections. In future correspondence regarding Systernatic Evaluation Program topics, please refer to the topic numbers in your cover letter. Sincerely,

Dennis M. Crutchfield, Chief Operating Reactors Branch f5 Division of Licensing 5 Enclosure: As stated THIS DOCUMENT CONTAINS 81 2 0% , POOR QUAUTY PAGES cc w/ enclosure: See next page %,- m v 1 ( ^ Yh ,S,EPB:DL T SEPB':DL:SL SEPB:DL:C' ORB DL PM gSA:DL omce > , OP[9 WRussell RCa' [email protected] D,Pers..i nko.:d < RHermann ,,j,,,, qLt]nas , , , , , ''""'"'> . 2 2/ _ /81 2/# /81 2/ /81 o^n > 2/3 /81 . , .., ...... 2/3. ../81 .. . . ./.J /81...... y...... ~nc rosu aio no.coinacu o24o OFFICIAL RECORD COPY "" "- 3 2"2 ', __ $ . ,.

gikS UGg J o UNITED STATES i NUCLEAR REGULATORY COMMISSION " | 0i h- . , h, f ' i,i WASHINGTON D. C. 20555 * , February 09, 1981 .....

| Docket tio. 50-29 L505-81-02-013

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' Mr. James A. Kay Senior Engineer - Licensing Yankee Atomic Electric Company 1671 Worcester Street Framinghan, Mass. 01701

Dear Mr. Kay:

SUBJECT: TOPIC II-3.A HYDROLOGIC DESCRIPTIOf4 AND TOPIC II-3.B, (PARTIAL), FLOODING POTENTIAL AND PROTECTION REQUIREMENTS (YANKEE ROWE) Enclosed is a copy of our draf t evaluation of Systematic Evaluation Program Topics II-3.A and II-3.B. You are requested to examine the facts upon which the staff has based its evaluation and respond either by confirming that the facts are correct, or by identifying errors and supplying the :orrected information. We encourage you to supply any other material that might affect the staf f's evaluation of these topics or be significant in the integrated assessment of your facility. Your conclusions regarding the subject topics and your seismic evaluation p- i c# the dan, should be considered together because of possible interrelationships between the subjects. Your response 1s requested within 30 days of receipt of this letter. If no response is received within that time, we will assume that you have no comments or corrections. In future correspondence regarding Systematic Evaluation Program topics, please refer to the topic numbers in your cover letter. Sincerely,

e , Dennis M. Crutchfield, ef Operating Reactors Branch =5 : Division or Licensing

Enclosure: As stated cc w/ enclosure: See next page

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Mr. J ames A. K ay YANr 'J:WE ATOMIC / FCW .ATION ; j DOCKmi N0. 50-29

CC Mr. Janes E. Tribble, President Yankee Atomic Electric Company , i 25 Research Drive ' Westborough, Massachusetts 01581 Greenfield Corrunity College 1 College Drive Greenfield, Massachusetts 01301 i I ( Chairren Board of Selectmen f T own of R ow a . Rowe, Massachusetts 01367 Energy Facilities Siting Council 14th Floor One Ashburton Place Boston, Massachusetts 02106 Director, Technical Assessment Di vi sion Office of Radiation Programs (AW-459)

, U. S. Environmental Protection Agency Crystal Mall #2 Arlington, Virginia 20460 U. S. Environmental Protection Agency Region 1 Office ATTN: EIS COORDINATOR JFK Federal Building Boston, Massachusetts 02203

Resident Inspector Yankee Rowe Nuclear Power Station c/o U.S. NRC Post Office Box 28 ) Monroe Bridge, Massachusetts 01350

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SEP CRAFT SAFETY TOPIC EVALUATION YANKEE R0WE NUCLEAR POWER STATION

TCPICS II-3.A. HYOROLOGIC DESCRIPTION TOPIC II-3.B, (PARTIAL), FLOODING POTENTIAL AND PROTECTION REQUIREMENTS

!. Introduction It must be assured that tne designs of safety-related structures, systems and ccnponents have considered appropriate hydrologic conditions. Hydrologic considerations include the interface of the plant with the hydrosphere,

the identification of hydrologic causal mecnanisms tnat may require special plant dasign or operating limitations. The scoce of these safety topic evaluations is to assure that appropriate hydrologic factors have been considered and to assess any hydrologic considerations which may have enanged since being reviewed during the initial licensing of the plant. Should flooding potential exist, the impact of the flood on the plant will be examined. 'It flooding protection is required, it must be assured that the protection relied upon is available, appecariate, and tnat provisions have been made to implement the required protection. The protection will be reviewed to assure tnat safety-related scructures, systems and ccmconents are pectected against floods.

II. Current Review Criteria The current NRC criteria applicable to these topics are (i) Standarc

. Review Plans 2.2.1 through 2.4.14, 3.4.1 and 9.2.5; (2) Regulatory Saides 1.102, 1.127, 1.27, 1.59 whicn includes American National Standards Institate Stancard 1170-1975, and Regulatory Guide 1.70. ..

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III. Related Safety Tooics and !nterfaces

The Topic. identifies water levels and other hydrologic information that may be pertinent to other review areas for assessment of effects on The related interface Topics safety-related buildings and ecuf pment.

are: (1) III-3.A Effects of dign Water Level On Structures; (2) I!-JE Cam Integrity; (3) *II-5 Seismic esign Consicerations; (1) VII-3 Systems Recuired for Safe Shutdown; (5) VIII-2 On Site Emergency power Systems - Diesel Generators; (5) XI-3 Station Service and Cooling Water Systems; and (7) XVI Technical Specifications.

The categories of "In Service Inspection of Water Centrol Structures" and , " Structural and Other Consequences of Failures of Underdrain Systems" also require hydrologic review and input; hcwever, the hydrologic aspects are accressed in Topics III-3.C anc III-3.3, respectively.

IV. Review Guidelines

a discussion of the potential flood related problems This report includes: at the plant site as a result of severe precipitation up to anc including 3recipitation (PMp) cn the Jesrfield the severity of the precaole Maximum i River Basin; a brief descriotion of the hydrologic features of the site | 1 ' and related surrounding area; a description of :ne analysis procecures used to predict the flood levels at tne site; ano a :iscussi:n af the

, study results.

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IV. Review Guidelines (cont)

As a result of the predicted possible severe flooding of the Yankee Rcwe Nuclear Plant Site, this report was expedited and is therefore limited to the ciscussion sf floccing potential for tne Deerfisic River !asin and The review of grouncwater, ::cai Yankee Rcwe Nuclear Piant Site. flooding and~ safety related water succly will be deferred an-il -he mere severe proc am cf Oc antial :eerfield River #1 cc ef'ects has ':een

assessed.

Regulatory Guides 1.59 and 1.102 have been specificaliy identified by the NRC's Regulatory Requirements Review C0mmittae as needing consideration for backfit on operating reactors. These guides are utili:ed in determining i l wnether the facility design ccmciies wita current criteria or same etu va ent alternatives sc:eptable to the staff

This evaluation was performed under the auspices of the Systematic Evaluation ?r: gram and is orepared as input to the Integrated Assessmert

Report.

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V. Evaluation

1.0 INTER-AGENCY CCORDINATION

The Federal Energy Regulatory Commission (FERC) has the licensing responsi- bility for Hydroelectric Developments. The NRC has previously met with FERC to apprise them of our preliminary findings. Interagency coordination

is also required between NRC and the Federal. Emergency Management Agency (FEMA) in accordance with criteria set forth in Appendix E, 10 CFR Part 80,

NUREG-0654 and tne Inter Agency Steering Committee. FEMA has also been apprised of our preliminary findings, and both agencies will be included on distribution for the completed draft flood study and any subsequent correspondence relating to the potential flood problem at the Yankee Rcwe site.

2.0 Discussion of Problen

The Yankee Rowe 'iuclear Power Plant is located on the east bank of the Sheman Dam and Reservoir, the fourth cam in a chain of hyar electric dams on the accer Ceerfield River Sasin (See Figures 3.1.1 and 3.1.2). These dams were constructed in the 1920s. The first step in the NRC's SEP review is to conpare the existing plant to current licensing criteria for

| new olants. Thus, in this study it is required to determine if, the Harriman Dam, the first upstream dam from the plant, can safely pass a Probable Maximum Flood (DMF) - ne current design basis for new nuclear power plants.

| Since tne failure of Harriman Dam coule induce damaging flood levels at the olant site, it is also necessary to estimate the magnitude of these ficed levels. |

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This flood study shows that although Harriman Dam can safely pass about 13 inches of basin rainfall, it does not meet current licensing criteria in that 18.9 incnes (the design basis Probable Maximum Precipitation based on current criteria) on the Upper Deerfield River 3asin sill overtoo and fail Harriman and Sherman Dams and produce ficed levels at the plant site that are 40 or more feet above pl3nt grade.

Tabulated below are several key evaluation areas that have a significant influence on the determination of flood level at the plant site.

1. Magnitude of precipitation in the basin.

2. Distribution of precipitation within the storm (t of rainfall in eacn 5 hour period).

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3. Magnitude ano timing of antecedent stonm1.

4 Reduction in Harriman Spillway capacity due to debris or reduced 4 hydraulic performance characteristics at heads greater than the design value.

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5. The shape and duration of dam breaches due to overtopping. ,

5. Early failure of Sharman Dam.

The significance of these items will be discussed further in Section 4.0.

( It should also be noted that failure of the Sherman Dam, which impounds the plant's normal and emergency water supply, could affect the plant's

safe snutdcwn capacility. This~ Js' bject will be addressed at a later date under Tcoic I!-3.5, " Safety Related ' dater Supply."

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- 3. 0 HYOROLOGIC OESCRIPTION

: 3.1 Yankee Rowe Site and Facilities :

. 3.1.1 Site Descriotion

The Yankee Rowe facility is located in the town of Rowe, in Franklin County, Massachusetts, on the east side of the Deerfield River, three- quarters of a mile south of the Vernant-Massacnusetts border. Figure 3.1.1 ,

i shows the site location on a general area map.

The site consists of approximately 2,000 acres straddling the Deerfield

. ' River in the towns of Rowe and Monroe, Massachusetts. The reactor facility

is located on the eastern side of the Deerfield River next to Sherman Dam and adjacent to the Sherman Reservoir, which serves as a source of cooling water for the Yankee plant's once-through condenser and service water

cooling system.

i Most of the land in the immediate vicinity of the site is heavily forested. I At the site, which is in a valley, the elevation is about 1130 feet above |

I mean sea level (feet msl). Within a distance of one mile, however, the i

, hills on both sides of the site rise to above elevation 2000 feet asi. This steep-slope character of the Deerfield River extends from Wilmington, Vermont,12 miles north, to Charlemont, Massachusetts,:'E miles south- ! southeast. t

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3.1.2 Station Description

The Yankee Nucitar >ower Station is a single-unit pressurized water reactor nominally rated at 185 MWe gross generating capacity with a rated net capacity of 176 MWe. The containment, a steel sphere elevated 30 feet above the ground, enclose. the entire primary system, including the steam

generators. The :tation has operated sinca July 1960, under Atomic Energy Ccomission license number CPR-3, issued under section 104(b) of the Atomic Energy Act of 1954 (as amended).

A once-through open cycle system with an average flow of 310 cfs is used for condenser cooling.

There is an 82.6-acre watershed southeast of the plant that drains across

the plant site to Sherman Pond. There is a 994-acre watershec located

' north and east of the main plant area. This watershed is drained by Wheeler Brook wnich empties into Sherman Pond just north of the main plant area. Flood potential from these two drainage areas and the plant

site will be deferred to a later report.

Yard grade in the vicinity of the plant proper is 1127.7 feet ms1 and 1119.7 feet msl at the screenhouse. Floor slab elevation of the turbine building is 1128.3 feet ms1.

Figure 3.1.2 illustrates the general layout of the station.

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3.2 Hydroschere - The Deerfield River Basin

3.2.1 General Descriotion

The Deerfield River, a tributary of the Connecticut River, has a total drainage area of 664 square miles and extends from southern Vermont into the northwestern corner of Massachusetts. The Yankee Rowe power station, situated on the central cortfon of the Deerfield River Basin (Figure 3.2.1) is only affected by hydrologic events in the 236 square afie drainage area of the upper basin.

The upper Deerfield River Basin, in general, has fairly steep slopes and comprises four sub-basins - Somerset, Searsburg, Harriman, and Sherman - which are delineated in Figure 3.2.1 by the bold dotted lines. The average Deerfield River flow for the 61 year record at Charlemont, Massachusetts, U) is 887 cubic feet per second . Charlemont is approximately 9 miles downstream from Sherman Dam and has a drainage area of 362 square miles.

' The maximum flow at Charlemont was 56,300 cubic feet per second recorded during the hurricane of 1938.

1 1 1 3.2.2 Descriotion of Vooer Deerfield River Reservoir Cevelocments

The Upper Deerfield Project includes the Somerset,:Searsburg, Harriman,

and Sherman Developments.

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The Deerfield River rises in Southern Vermont and flows generally in a south and east direction through a valley that is narrow at the headwaters but broader as it approaches the entrance to the Connecticut River. At the Somerset Reservoir Dam in the upper reaches of the river, the eleva- tion is 2134 feet msl and at its confluence with the Connecticut River its elevation is 120 feet msl, a drop of 2014 feet.

$_cmerseto Reservoir

The drainage area above the dam is approximately 30 square miles. The reservoir extends upstream for approximately 5.6 miles and has a surface

area of about 1623 acres .rt elevation 2133.6 feet ms1.

The spillway structure is located at the west end of the earth embankment. It consists of a trapezoidal concrete section divided into eight bays, each 24 feet wide with a crest at elevation 2133.6 feet msl, and two 10-foot wide sections with crest at elevation 2133.6 feet msl provided with stop logs to elevation 2136.6 feet ms1. A creosoted timber bridge spans the spillway on concrete piers. New flashboard stanchions were installed in 1964 to carry three feet of flashboards. The spillway discharges into a channel excavated in ledge. The channel is about 800 feet long, 45 feet in average width, and from 6 to 30 feet deep.

The Somerset Dam is of the semi-hydraulic fill type and is constructed on

a curved alignment. The entire upstream siope is protected by riprap. i The roadway at the crest is of gravel construction.

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River flow leaving Somerset Reservoir flows south through the East Branch of the Deerfield River to the Searsburg Reservoir.

Searsburg Development

The drainage area above the development is approximately 90 square miles.

The pond, extends upstream for approximately 1 mile and has a surface area of about 28 acres at elevation 1754.7 feet msl.

The spillway consists of a concrete ogee weir 137 feet long with crest at elevation 1749.7 feet ms1 and provided with pin type flashboards 5 feet in height. A bypass channel used during construction is located at the northerly end of the spillway, and closure in this area consisted of a vertical concrete wall and deck.

The earth embankment at the northerly end of the dam is of the semi- hydraulic fill type, supported by a gravity concrete retaining wall. The roadway at the crest is of gravel construction.

Because of the limited storage capacity (293 acre-feet), the failure or non-failure of this dam will have no appreciable effect on downstream ficod flows. Therefore, this dam and reservoir were ignored in subsequent flood analyses.

Figure 3.2.3 and Table 3.2.1 show some pertinent features of the dam and reservoir.

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The flow continues downstream in a south and east direction into Harriman Reservoir.

Harriman Develcoment ,

The drainage area above the development is approximately 184 square

miles. The reservoir extends upstream for approximately 9 miles and has a surface area of about 2050 acres at elevation 1492.7 feet asi.

The 200-foot high earth dam is of the semi-hydraulic fill type and was raised with rolled earth fill from elevation 1511.7 feet asi to elevation 1521.2 feet msl in 1964 to increase flood retention capability. The upstream slope has riprap protection to elevation 1480.7 feet ms1 for most of the length of the embankment, varying to elevation 1495.7 feet msl at the northerly end. The roadway at the crest is of gravel covered

with a seal coat of asphalt. The downstream slope has a grass cover.

; The spillway is of the morning glory type and is located upstream of the southerly end of the dam. The spillway discharges througn a 22.5-foot minimum diameter vertical shaf t and 90 degree bend into the concrete bypass conduit that was used for diversion during construction. The bypass conduit is now plugged with concrete upstream of the vertical shaft. This conduit has a cross-sectional area equivalent to a 22.5-foot diameter circle. The spillway has a crest elevation of 1491.7 feet ms1 and 16 equally spaced piers that can accommodate 7 feet of flashboards. The spillway shaft and crest were resurfaced in 1954.

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Figures 3.2.4 and 3.2.5 and Table 3.2.1 show some pertinent features of the dam and reservoir.

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Flow leaving the,Harriman Dam continues downstream in a southerly direction i into Sherman Reservoir.

Sherman Develeccent

The drainage area above the ce.:topment is approximately 236 scuare miles. The pond extends upstream approximately 2.2 miles and has a i surface area of about 194 acres at elevation 1103.7 feet msl.

The dam is of the semi-hydraulic fill type and was raised 10 feet to elevation 1129.7 feet msl with rolled earth fill in 1964 in order to increase spillway capacity. The embankment is supported at its northerly end by a concrete retaining wall which also was raised in 1964. The upstream slope has riprap protection to elevation 1095.7 feet msl for the full length of the embankment. The downstream slope has grass cover over its entire area.

The spillway structure is Itcated at the north end of the dam. It consists of a gravity concrete agee weir section with a crest elevation of 1103.7 feet msl and is provided with pin type flashboards 4 feet in height. There is a spillway channel, excavated in ledge, about 360 feet long and 50 feet wide spanned by a plate girder bridge. The spillway channel was deepened in 1964 by the removal of 4600 cubic yards of material to increase discharge capability by reducing backwater effect. An eroding area downstream of

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. the spillway bridge or *.he west side of the charnel was graded and riprapped

at the same time. A concrete bypass conduit, used during construction, runs through the earth dam. This has a cross-sectional area of 140 square feet and has been plugged at th'e upstream end with concrete.

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Figures 3.2.6, 3.2.7, and 3.2.8 and Table 3.2.1 show some pertinent features of the dam and reservoir.

3.3 Floods

3.3.1 Flood History

The flood history of the Deerfield River during this century is readily available from records which extend back to 1911 when construction began on the hydroelectric facilities. These records and those from the U.S. Geological Survey gaging station at Charlemont clearly document major storm and discharge events which are summarized in Table 3.3.1.

As shown, the most significant event was during the "1938 hurricane," closely followed by the 1948-49 "New Year's Eve" storm, and the 1927 and

1936 events. Although undocumented, a local reference (2) states that the ficod of Oc:cber 1869 was similar in severity :: the 1927 event. The ' , rainf all wnich accomoanies tropical stoms (including hurricanes) of ten

' produces major floods during the summer and early fall. Extratropical

. storms and/or snow melt produce principal floods during the winter and | , I spring months.

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Maximum average depths of rainfall for selected historic storms of record for the region are shown in Table 3.3.2. These actual storm values are presented as an Indication of what has occurred in the region histori- cally. Also shown is the controlling storm for the northeast United States (OR 9-23), commonly known as the Smethport, Pa. storm. This storm occurred on the west side of the Appalachian Mountains and is generally

not transposed across the mountains.

4.0 Analysis Procedure

4. ! General

In order to determine the Probable Maximum Flood (PMF) elevation at the Yankee Rowe Plant site, the Probable Maximum Precipitation (PMP) is applied to individual subbasins using a unit hydrograph to define the runoff cnaracteristics of the subbasins. The hydrographs thus obtained are routed through the stream channels and reservoirs to account for

attenuation due to channel and valley storage. Wnere dams are overtopped c the erosional failures and resulting outflow hydrographs are simulated by j synthetic methods.

, | | The PMF is used by many federal, state and local agencies and architectural engineering firms to predict upper limit flood levels for planning ar.d ! The PMF is defined as "The hypothetical flood (peak | design purposes. I | discharge, volume and hydrograph shape) that is considered to be the most severe reasonatly possible, based on comprehensive hydrometeorological acplication of probacle maximum precipitation and other hydrologic f actors

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favorable for maximum flood runoff uch as sequential stcrms and snowmelt."( ) The PMP is defined as "The estimated depth for a given duration, drainage area, and time of year for which there is virtually no risk of exceedance. The PMP for a given duration and drainage area approaches and approximates the maximum which is physically possible within the limits of comtemporary hydrometeorological knowledge and techniques."(3)

On a complex river basin such as the Deerfield where multiple water levels and sensitivity analyses are required, a computer model is used. In this case, the HEC-1 Flood Hydrograph Package for Dam Safety Investigations ( )

was used.

The basic HEC-1 Flood Hydrograph Package was developed by the ll.S. Army Corps of Engineers' Hydrologic Engineering Center for modeling basin

stream networks. This computer program is used by many federal, state and loca.1 agencies as well as architectural and consultant engineering firms. The dam safety investigation program is a modification to the basic program that allows the estimation of the overtopping potential of a dam and the downstream hydrologic-hydraulic consequences resulting from assumed structural failures of a dam.

4.2 Rainfall and Runoff

4.2.1 Procable Maximum Precioitation

The staff considered several sources for the PMP for this study.

HydrometeorologicalReportNumoer33(H.R.133), April 195d0) , is the

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source most commonly used for PMP estimates east of the 105th meridian. This report was revised and expanded and released as Hydrometeorological Report Number 51 (H.R. #51)(6) in June 1978. H.R. #51 predicts slightly larger rainfall values for the study area than H.R. #33. Since H.R. #51 has not been fully reviewed by some major federal agencies such as NRC, we have not used precipitation estimates from H.R. #51 for the study.

The licensee, Yankee Atomic Power Company, has recently completed a Oraft Probable Maximum Flood Analysis for the Yankee Rowe Nuclear Generating Station.(7) This report attempts to derive a PMP for the Upper Deerfield River Basin by transposing and maximizing several maximum regional storms to the Deerfield Basin. The NRC staff has not accepted this analysis due to the lack of supporting data and apparent erroneous transposed storm rainfall values. The staff assertien of erroneous results is based in part on the staff's independent analysis of the Westfield storm which resulted in rainfall estimates considerably larger than the licensee's

estimates.

NRC regulations do not specifically require a PMP for the Cesign Basis Flood for nuclear power plants. Title 10, Part 50, Appendix A of the Code of Federal Regulations states, "The design bases for these structures, systems and components shall reflect: (1) appropriate consideration of the most severe of the natural phenomena that have been historically reported for the site and sourrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historic data have been accumulated." In order to be assured that the licensee

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is not being unduely penalized by the use of Generalized PMP values, the staf f made an independent analysis of the August 1955 storm that was centered at Westfield, Mass. (about 50 miles south of the Rowe site). The maximization,and transposition of this storm to the upper Deerfield River Basin provides a rainfall estimate that can be considered as a lower limit value for a design basis flood.

The storm was maximized and transposed to the Deerfield Basin using procedures suggested in H.R. #51(6) and the manual for Estimation of OS) Probable Maximum Precipitatien . The transposed storm had an adjustment factor of 1.17 which includes factors of 110% for moisture maximization, 89% for transposition and elevation and 120% for orographic effects. The 200 square mile, 24-hour adjusted rainfall for the storm is 16.6 inches. Depth area-duration curves for the transposed Westfield Storm are shown on Figure 4.2.2. An idealized isohyetal storm pattern, witn this rainfall, was centered on the upper Deerfield River Basin and planimetered to obtain an average 236 square mile basin rainfall of 16.5 inches for 24 hours. The resulting flood runoff would overtop Harriman dam and produce a flood level at the Yankee Rowe site of 1172.4 feet msl. It is noted that this lower limit rainfall value by itself does not qualify as a FMP. It follows that a comprehensive regional PMP study would predict at least 16.6 inches for the 200 square mile, 24-hour value and would probably predict a somewhat larger value but less than the 18.9 inches from

H.R. #33. Since this lower limit rainfall does not alter the conclusions of this study, it was concluded that the rainfall from H.R. #33 would be used as the design basis rainfall for this study.

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The depth area-duration curves from H.R. 433 for the upper Deerfield River Basin are shown in Figure 4.2.1.

The distribution,of rainfall in the worst 6-hour period has a significant influence on the potential flood levels at the Yankee Rowe site. H.R. #33 suggests that 72.8% of the 236 square mile, 24-hour rainfall occurs in the critical 6-hour period. Referring to Table 3.3.2, the maximum 6-hour values for these historic storms range from 43 to 66 percent of the 200 square mile, 24-hour value. This percentage ranges up to 00% for northeast U.S. storms shown in reference (6). For a sensitivity test, the model was run with 43% of the 24-hour PMP in the maximum 6-hour period. The results of this run show that Harriman Dam would still be overtopped and the level at the Yankee Rowe site would increase by 8.0 feet. The reason for the higher stage at the site is because the higher percentages of rainfall in the critical 6-hour period causes Sherman Dam to overtop and fail.about 4 hours before the peak outflow from Harriman Dam reaches the Yankee Rowe site. Whereas witn the 43% distribution, Sherman Dam does not fail until the peak outflow from Harriman Dam reaches the site. This higher initial Sherman reservoir level induces a higher peak flood stage at the Yankee Rowe site. The rainfall distribution suggested in H.R. #33 was selected for use in this flood study. , | l 4.2.2 Rainfall Losses

Rainfall loss rates can be derived from historic storm and flood records. The loss rates thus computed would generally be directly applicable to

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maximized storms such as the PMF. The licensee derived loss rates in Reference (7) from two historic Deerfield River storms. The computed rates were 0.03 and 0.06 inches per hour. Other verification evaluations (7) indicated about 0.1 inch per hour. We discussed rainfall losses with personnel from the New England Division of the U.S. Army Corps of Engineers who have studied many storms in the region. They recommend a loss rate of 0.1 inch per hour and no initial loss for a PMF study. Based on our own experience and the information supplied by the licensee and the Corp of Engineers, we selected a loss rate of 0.1 inch per hour and no initial loss. The licensee used an initial loss of 0.5 inch and 0.1 fach per hour for his PMF study.(7) Since the PMF by definition optimizes and maximizes parameters, the use of no initial loss is justifiable and

reasonable. Additionally, the losses are a small part of the total rainfall and do not have any significant effect on subsequent flood levels.

4.2.3 Unit Hydrocrach Coefficients

The Unit Hydrograph is "the hydrograph of surface runoff (not including groundwater runoff) on a given basin, due to an effective rain falling for a unit of time. The tarm ' effective rain' means rain producing surface runoff. The unit of time may be one day or preferably a fraction of a day. It must be less than the time of concentration." Unit hydrographs can be derived frcm actual storms or by synthetic methods using empirical equations. For this study, both methods were used to derive unit hydrograph coefficients. Several synthetic methods from the

18

s * i . sJ b . *.. d

literature were used to derive ' coefficients for eacn of the four subbasins discussed in Section 3.2.2. The methods used were: (1) Snyders Equation (EM 1110.2-1405)(9) , (2) Design of small Darrs(10) , (3) Linsley, Kohler and

, Paulhus OI) , and,(4) Standard Project Flood Criteria, Southern California (12) Another set of coefficients were derived from & historical hydrograph U) presented in the Licensee's studies . Unit Hydrograph coefficients were also develcped from information obtained in discussicos with personnel of the New England Division of the U.S. Army Corps of Engineers wno have done many similar studies in the region. Another set of coefficients were selected based on personal observation and experience.

Ultimately, a set of Clark Unit Hydrograph Coefficients were selected for each subbasin based on professional judgment, personal experience, and

with due consideration of the values obtained from the above methods. Prior to the completion of this study, the licensee also furnished Snyder Unit Hycrograph Coefficients for each subbasin. The Snyder values were derived from actual storms and verified in other storm reconstitutions. The following table shows a comparison of Snyder and Clark coefficients for the NRC and licensee values:

UNIT HYOROGRAPH COEFFICIENTS DEERFIELD RIVER BASIN COMPARISON OF NRC AND YANKEE ATCMIC VALUES Clark Coefficients 1/ Drainage SnyderCoefficientsl Subbasin NRC fankee Atomic E Yankee Atomic R TP CP TP CP - .T c R Tc Somerset 2.42 .56 2.68 .81 2.7 2.7 10.37 3.65 Searsburg 3.09 .57 2.98- .81 3.4 3.4 11.50 4.09 Harriman 4.09 .58 4.16 .81 4.4 4.4 16.79 5.14 Sherman 3.17 .57 3.23 . 81 3.5 3.5 12.86 4.22

1 onversionsC from Snyder to Clark and visa versa were cone with the HEC-1 program (4) 19

-_ _ .

* 1 ,

DR!ET

, The scmewnat large Yankee Atomic Clark coefficients reflect the sicwer i times of cancentration that the licensee obtained in the case studies. The runoff hydrographs developed from the Yankee Atomic coefficients will ' be broader and flatter (lower peak discharge) than the hydrographs developed with the NRC coeff!cients.

Table 4.1 shows a comparison of output frcm sensitivity studies run with the nEC-1 model. This comparison shows that the choice of unit hydrograph coefficients has little effect on resulting flood levels. However, in the interest of conservatism, the staff's final results and conclusions are based on the model runs using Snyder coefficients furnished by the licensee. Additionally, unit hydrograph coefficie'nis derived and verified with actual flood events are generally more acceptable to the technical

community.

The HEC ,1 model is used to develop runoff hydrograpns for each subbasin frem the unit hycregrapns, the rainfall, and rainfall' losses. These

' subbasin runoff hydrographs are then in turn routed through the channels

1 and reservoirs in the river basin.

. .

Y

1

>

t

, g

20

, . - - -_ a _ - _ _ _ _ ._, . - . . . - _ _ _ . , , ,

.

4.2.4 Maximum Regional Rainfall It is common practice, when analyzing potential flood problems, to determine the maximum historic rainfall for the region.

Table 3.3.2 shows the maximum recorded rainfall values for storms that have occurred in the region. The Westfitid, mass storm (No, MA 2-22A) is the largest storm in the region by a considerable margin.

, This storm was transposed to the Deerfield River Basin for the purpose of determining the potential effect on Harriman Dam and the Yankee Rowe Nuclear Plant. The transposed storm would have a 24 hour average basin (236 square miles) rainf all of about 13 inches.

, 4.3 Floed Routing The channel and reservoir routing with the HEC-1 model uses the mcdified Puls method. This method of routing accounts for hydrograph attenuation ;

- due to channel, valley, and reservoir storage, but it dces not account for the time required to convey water from one subbasin to the next. Above Harriman Dam this is accounted for in the subbasin hydrographs;

,

S

20a

- . _ _ . _ . . . _ _ . ______. _ - _ . _ _ . .

' ,

e

[l ? L ii' .; l [fi"I

between Harriman and Sherman Dams it is not. We estimate this time to be about 1.5 hours between Harriman and Sherman Dams. Thus, in terms of predicted flood levels at the Yankee Rowe site the peak inflow hydrograph to Sherman Reservoir could lag the predicted arrival time by less than 1.5 hours. In most cases analyzed, Sherman Dam is predicted to fail prior to the arrival of the predicted failure

hydrograph from Harriman Dam. Therefore, any delay in the arrival of the Harriman peak flow could result in somewhat lower flood levels at the nuclear plant site. However, any failure hydrograph from Harriman Reservoir is sufficient to cause significant flood levels at the site, regardless

of when Sherman Dam fails.

4.3.1 Reservoirs Routing

Reservoir routing was done by the Modified Puls method. Reservoir storage curves were provided by the licensee. The storage curves for Somerset, Harriman, and Sherman Reservoirs are presented in Figures 4.3.1, 4.3.2, and 4.3.3, respectively. The curves have been conservatively extrapolated | I by the itsensee above the top of dam levels using an incremental storage

| i procedure.

Reservoir outflows were of three types: (1) discharge through the normal reservoir spi 11 ways or outlet works, (2) discharge over non-eroded portions , of the dams, and (3) discharge through the eroded or breached dam sections. -

The spillway rating curves for Somerset, Harriman, and Sherman Reservoirs _ were furnished by the licensee and are shown in Figures 4.3.4, 4.3.5 and 4.3.6, respectively.

21

-- . .- . - ._ . _ _ _ .-- - .

, ,.

s

I The staff has some reservations with resoect to the spillway Tor Harriman Reservoir. This spillway is the " Morning Glory" type which is designed to operate with a small change in discharge ~for a large range in heads. The scillway is located in the corner of the reservoir and very close to the dam and soutnern bank of the reservoir. This location would be conducive to debris accumulation and potential blockage, escecially for rare floods that will carry many large trees and other debris downstream. These spillways are also noted for undesirable discharge characteristics at reservoir levels above the design value. The Harriman spillway was , designed for a reservoir elevation of 1493.6 feet ms1. The dam has been raised subsecuently, and predicted levels could be as high as elevation 1525 feet msl. When these type spillways are subjected to heads above the design value, there is possibility of shifting control between weir, orifice and full pipe (pressure flow) with the associated uncertain dis- charge capability, slug ficw, vertices, cavitation, and vibration. There is another uncertainty with resoect to the rather narrcw discharge channel immediate'.y downstream of the tunnel outlet. The unknown is whether the narrow channel could submerge the outlet at higher flows, thus forcing a hydraulic jump in the conduit and thus reducing capacity.

. During past meetings with the licensee he has denonstrated a willingness to construct booms or other considerations to preclude debris frca the spillway if the additional capacity would ensure non-overtopping of i Harriman Dam. The spillway was model tested in 1925 prior to construction. The model test does mention some runs at higher heads and the associated

vortex fornation and scme fluctuation in discharge. It is doubtful that the friction in the riser and barrel were crecerly mcdeled and even if

22

-. -- .. - . . -- - i

'fa. e -. .< ~2-.T!!. ]

they were it is very difficult to predict, with a model, the flow charac- teristics for this type of spillway, for greater than design conditions. In light of the many uncertainties with this spillway, we limited the assumed discharge to the capacity of the riser throat as an orifice. This is about a 25% reduction in capacity at the higher heads.

The spillway for Sherman Dam has a rather narrow discharge channel downstream of the crest. Downwater computations for this spillway indicate the possibility of hydraulic jumps or turbulent flow conditions at very high discharges. Depending on the resolutions of other more serious problems, this issue may be investigated more thoroughly at another time.

Discharge over the non eroded dam sections is computed by the HEC-1 program using the standard weir equation.

The breach hydrograch is computed by a weir flow ecuation appropriate for the shape of breach selected.

4 These various possible outflows are summed by the program and used in the routing procedure.

41.2 Channel Routing

The only channel routing required in the model was from Harriman Dam to , the Sherman Reservoir. The geometric elements for the routing cross

..

23

. - - . _ - _ . - - _ . _ - .-. . _ _ . _ - _ _ _ . , ,

,

'-:tit e.e,i., r p -|e L?i'd'il I

section were obtained from a 1:62,000 topographic map. The cross section was used for a one step Modified Puis routing to attenuate the hydrograph for channel and valley storage between Harriman Dam and Sherman Reservoir.

. 4.3.3 Antecedant Floods

Our current criteria requires that when analyzing potential single or multiple dam failures during a PMF, that the PMF be preceded 3 to 5 days by a flood equivalent to 40% of the PMF. The purpose of this requirement is to allow for the estimation of the loss of reservoir flood storage capacity by antecedant floods. For this study the antecedant flood was routed separately. This routing indicated that all reservoirs would be at the spillway crest elevation at the start of the PMF. Therefore, all subsequent runs were started with the reservoirs at the spillway crast elevation, except Searsburg, which was not considered as a reservoir as

discus se.d in Section 3. 2. 2.

4.4 Erosional Dam Failures

As discussed in Section 4.1, the Modified HEC-1 program has provisions to ; simulate erosional type dam failures. The program allows for user discretion in selecting the shape and duration of the breach. Two breach shapes (trapezoidal and triangular) and three durations (1, 2 and 3 hours) were

modeled for both Harriman and Sherman Dams in order to determine which would be critical in terms of water level at the Yankee Rowe site. The side slopes of both triangular and trape:oidal breaches were assumed to

24

_ . _ _ . ._ -- .- - . _ ' .' |

| . . i

U t. b |

be the angle of repose (g) of the enbankment material which was assumed to be

35 . The bottom width for trapezoidal sections was assumed to be the width of the natural valley at the toe of the dam, and the lower limit of the eroded sectigns was assumed to be limited to the elevation of the natural valley at the dam site.

The results of these analyses showed that the trapezoidal shape for a duration of one hour would be the critical assumptions for both dams. Since the duration of the Harriman Dam breach has a significant influence ' on the depth of flooding at the Yankee Rowe site, the TVA Breach Model was used as a method of quantifying the duration of breach.

The Harriman inflow hydrograph for the TVA model was obtained by routing the PMF with the HEC-1 model and assuming infinite dam heights. Other inputs to the model were a 0 angle of 15 degrees and a breach width of 400 feet. The section was eroded to elevation 1320 feet asl which is the approximate natural valley flour elevation. The model results showed a time of about one hour to breach the section.

Unfortunately, there is only a limited amount of information available on methodology for simulating erosional failures of earthen embankments. To the best of our knowledge, the TVA model is the only one available that attempts to predict a rate of failure. There is some historic information available, but at best this cnly supports the unpredictability of this - type of dam failure. Photographic documentation of the recent Teton Dam failure indicates that the rapid failure of a large portion of the embank- a ,t secti]o occurred in abcut 23 htes. Al t ah this as not an

25 i i

, - , , , ._- - .- -- - . - . .

* ! .

.-;l' E [i. b ' ;

overtopping breach, the rapid failure of a major portion of the emcankment

! gives a good indication of the erosional potential of reservoir storage.

4.5 Recurrence Intervals of Natural Phenomena

Recurrence intervals or probabilities of natural chenomena (rainfall or flood events) are often used as a decision-making tool. The staff is : reluctant to attempt to associate frequencies with rare natural phenomena due to the large confidence intervals and the tendency to place more reliance on the probability estimates than is justified by the basic data. However, there is some frequency information available for rainfall in the region, and it is included in the following paragraphs.

Technical Paper #40(16) , which does not include the last 24 years of records ! nor the effects of Hurricane Diane, shows a regional 24 hour-100 year point rainfall for the 2eerfield River Basin of about 6 inches. The Westfield gage (about 50 miles south of the Rowe site) recorded rainfall during Hurricane Diane; the 24 hour-100 year point rainfall for this gage is 12.4 inches. The Springfield gage, which is about 10 miles east of Westfield, has a 24 hour-100 year point rainfall of 8.5 inches. The ;. licensee has provided scoe rainfall frequency information in pcpendix A

I ' of N ference 7. They shcw a 24 hour-100 year point rainfall for Harriman " 2n of about 5.6 inches. The other gages they selected all have

' :ur-100 year point rainfalls of between 4 and 6 inches. However, did not select any sites in the region that have recorded severe ical rainfall events, such as '.'estfield, Mass. , Kinsman Notch, er $pr ogfield, " ass.

26

|

. - . - . . -. . . _ . - . _ . _ _ - _ _ . . - - _ _ _ _. . - _ .. . - -

' ' .

' .% .=t w '. '

( . .. .1

Basee on consideration of the above 100-year rainfalls, it is the staff's ,

' judgment that the regional 24 hour-100 year point rainfall for the Upoer Deerfield River Basin would be about 7 to 8 inches. NOAA Technical Report NWS 24II7) provides a generalized curve for converting point rain- falls to area rainfalls. The 8-inch point rainfall is equivalent to 7.4 inches on the 236 square mile basin. This then can be compared to

' the 13-inch basin rainfall that Harriman Dam can safely pass. The only guide we can sugces for putting the 13-inch rainfall into a frequency perscective is tnat the 13-inch rainfall is approximately a recional > record value, and based on past experience of other record storms and their

4 extrapolated frequencies, which introduce significant uncertainty, the recurrence intervals are generally in the 500 to 1000 year range.

It should also be noted that this probability information deals only with the rainfall event and makes no allowance for any conservatism in our methods of determining the PMF, sucn as locating the storms critically over a soecific watershed.

2 The percent chance of a rainfall value being exceeded in the next 20 years can be determined mathematically, There is an 185 chance of the 100-year (7. A inch) rainf all being exceeded in the next 20 years. For the 500-year and 1000-year recurrence interval rainfall (13 inches), there is a 45 and

! 25 .aance, resoectively, of being exceeded in the next 20 years. Again, it is noted that there is much uncertainty involved in trying to associate frequencies with rare natural phenomena. The above accroximate analysis ,;

is only intended to provide " ball park" estimates of the likelihood of, .. ; ! exceeding the existing capacity of Harriman Dam in the next 20 years. ; i 27

! i

. _ _ _ _ _ - . _ _ , , - . _ _ _ _ _ - . ______. _ _ _ _ . _ . . _, , . ,

,. ..-

*L.

; 5.0 Results This flood study has analyzed floods for a range of rainfalls from 13.0 to 21.3 inches. The resulting flood levels at the Yankee Rowe Nuclear plant site and other outputs are shown in Table 4.1. The 18.9 inches is the 24-hour, 236 square mile PMP from H.R. 433. It is the staff's judgment that, under current criteria, the P'iF based on this rainf all or rainfall derived from a detailed regional study as discussed in Section 4.2.1 is the flood that the Yankee Rowe plant should be protected against.

The flood resulting from 13 inches of rainfall on the basin is approximately what Harriman Dam can contain without overtopping. However, the reservoir

! level for 13 inches of rain would be at the top of the dan and does not ! include any allowances for coincident wind generated waves which would be about 3 feet high for a 30 to 40 moh wind and the runuo would be about 8 feet above the cond level. Additionally, the upoer 25 feet of the embankment does not have riprap for erosion protection.

The PMP (18.9 inches) used for the PMF would have a point rainfall of 25.6 inches which ccapares to a maximun 24-hour ooint rainfall on the

Harriman subbasin of 5.5 inches (Table 3.3.1) that croduced the record reservoir level of 1498.1 ft msl. Regionally, a 24-hour, 200 square mile value of 14.2 inches (Table 3.3.2) was recorded at Westfield, itassachusetts, just 48 miles south of the Harriman Dam. This storm when maximized and | [ transposed to the Upper Ceerfield River Basin would yield about 16.6 inches of rainfall in 24 hours for a 200 square mile area. .

23

- _ _ .. _ . - -

. . ,

( c' ; . q- '" - i: . . .: .; ,

Hydrcmeteoroicgical Report Number 33 is recognized by major water resources engineering groups throughout the country as the source for Probable Maximum Precipitation for the design of large dams whose failure could

. result in loss of life and major property damage. In lieu of rainfall i values based on a comprehensive regional study, the generalized estimate

from HR .133 is the value that should be used for the Probable Maximum

| Flood for the Yankee River site.

Table 5.1 compares pertinent values of other Ceerfield River ficed studies to the NRC Flood Study. The values for the C. T. Main (1977) and Yankee Atomic (1977) studies were taken from a report prepared by the Yankee

Atomic Electric Company, YAEC-1139(I4) . This report was prepared for the Federal Power Commission (FPC) (currently known as the Federal Energy Regulatory Ccemission - FERC) as part of their licensing requirements.

The C. Ts ''ain- values are similar to the NRC FMF values, except for the breach assumptions for the dams which have a significant influence on the resultant predicted maximum reservoir levels. Since the C. T. Main breach assumptions were not provided, we cannot discuss the comparison.

, i The Yankee Atomic (FPC Report) values are considerably icwer than curs,

" and we attribute the difference to the unit hydrographs, rainfall icss rates, and starting pool levels. In all cases, we consider the Yankee i

, At:mic values to be nonconservative.

The values for the 1980 Yankee Atomic flood study were taken from

4 refer +nce (7). The significant difference between these values and the

RC ~"c .i'aes is c e FMP r:' f all Oce secti:n ".2.1). " . ce affferen u

.

29

- -. .. -- . . . ------_ - _ - - . . - _ . ,

, . ,

. , ; .. .

. . ., r. h' -. r I

are in the Harriman spil'.waj capacity (100%-licensee vs approximately

75%-NRC) (See Section 4.2.1).

The values for the U.S. Army Corps of Engineers (COE) 1963 study were taken from a letter report that is. attached as Appendix A. The study resulted from interagency coordination on licensing requir9s: ants in 1962

and 1963. The COE study was for a spillway Design Flood (50F) for Scaerset, Harriman, and Sherman Dams. The SDF is equivalent to the PMF except that the rainfall would be for the drainage area controlled by each dam. . Their study also assumed infinite dam heights. The CDE values indicate that the results are very close to the NRC PMF study.

In addition to rainfall-induced floods, the site may also be exposed to flood waves from a Harriman Dam failure induced by other causes such as-

seismic, piping , etc. For these type failures the staff generally

assumes instantaneous removal of the dam section and :cdaling of the flood wave by unsteady flow techniques. Since only 100-foot topographic mapping is available for a portion of the reach and accurate cross sections cannot be prepared, the use of the unsteady flow model is not warranted.

| Therefore, the staff used approximate methods to estimate a water level i ' of 1143 feet asl at the Yankee Rowe site assumino instantaneous failure i af the Harr iman Dam with the pool at elevation 1493.0 feet :sl and 50% . | i ! ittanuation fue to channel and talley storage. : I ! The 13 inches of rainfall that Harrican Dam can contain without overtepping

8 is at:ut 70 per: ant of the 13.9 inch P"P used by NRC as the design bases

-* # ',-ir ' ,i t :"P . je' :c : . .. t3 i. :t .; c: .: s , cant :f ;"a

I

20 .

F

,,,...------m- . ,,,..,. ., y_,-- , -,--,..,,.-,--.-,-,7,- e p3 ------+.%-,-e,.o ,r-e- - - - -,. _- . . ,,wi---.. m n .,y y+-.s . - , . . . .

, . - - -

.

.. n - . . .. -

The 5.5-inch maximum 24-hour point rainfall at value of 15.5 inches. Harriman Staticn is about 22 percent of the 25.5-incn, 24-hour point

rainfall from H.R. #33.

. The significance of the difference in assumed Harriman $pillway capacities (100% vs 75%) can be cuantified by converting the ciffererce in discharge , : +cuivaient reservoir stcrage. The difference between ICC5 ard 75% 10,000 cfs. This ! spil!Nay cischarge at the t:p af dam a evation is a cut ' :w f:r about 5 hours is equiva!snt to abcut 2-1/2 feet of reservoir f r storage. The 13-inch rainf all above Harriman Dam wcuid maintain the reservoir within 2 feet of the : p of the dam for a: cut 5 hcurs.

VI. Conclusions and Reccmmendations

t 1.0 Hydrologic Conclusions

3ased :n : e results of the NRC Ficoc Study, it is One 3 aff's fucement

4 na: :ne "ar-iman Dam can safely : ass tr.e runoff from a 3 Orm si:n en

4 tverage u::er casin rain' ail :f 3:cu 13 incnes. :: i s 'uriner ::nclucec . ! ! :nat this storm nould result in a maximum flecd elevation at :ne Yankee

|

! 10we site of no mere than 1132.0 feet msl. This rainfall is about 70 NRC if censing criteria t : ercent of :ne design basis rainfall under curren i f r new :lants. i I f I ' ! e staf' also ::ncluces that if the tc;er :eerfiel: River 3asin is s..:jec.20 to a st rm vit. average :1-hour casin rai-f al :f u:n Ore than 13 'nches, that Harriman Cam will be overt:c;ec ar.: will f aii. The failure of Harriman Oss for any reason wnen the ; col is a:cve elevation !;90 feet asi 4ill ;r:dcce a ficed level at t'e Yankee ?:we site that is

, .._. ... , . . :... ,...... , ,.. ,,., , ...... , ...... -. .

I* ..

--- .r .u.- --.e,vww.-,,ww -y- ---,er,,-e-,--.,4-.- .,-=3w--w- - - - . - . > - , . --w-y w-- w e&- y t,-,- ,-,-m.-- --- 3 % e-- .y+.-- _ . . . -. - -- ...... - . - -

- .- ,

! ~ * . . . ,

- . ; ,

Y Current practice by designers and constructors of major dams, especially where there is a potential for loss of life or major property damage, is to provide sufficient storage and spillway capacity to safely pass a

' Probable Maximum Flood or its equivalent. Harriman Dam is a large dam, and

, there is potential for loss of life and major property damage in the event of a failure of the dam. If the dam were being constructed today,

' it would probably be designed to safely pass the PMF.

4

The Federal Guidelines for Dam Safety state:

- "C. Flood Selection for Design (or Evaluation) - The selection , of the design flood should be based on an evaluation of the relative risks and consequences of flooding, under both present and future conditions. Higher risks may have to be accepted . ! for some existing structures because of irreconcilable conditions. When flooding could cause significant hazards to life or major property damage, the flood selected for design should have virtually no chance of being exceeded. If lesser hazards are involved, a smaller flood may be selected for design. However, ali dams should be designed to withstand a relatively large flood = ' without failure even when nere is apoarently no downstrean nazard under present conditions of develocment."

Therefore, based on the results of this NRC Flood Study and on the Federal ; Guidelines for Dam Safety Harriman Dam should probably be considered for

' upgrading.

' 32

,

1

-. . . - .------.- _- - - _ - . . - _. . . _

' * r ,

.

,

4 ! 2.0 Recommendations The staff has considered possible remedial measures for the potential flood problem at the Yankee Rowe site. The best "fix" would be either , an emergency spillway in the west abutment of the Harriman Dam or a diversion to divert excess flows to an adjoining drainage basin. The emergency soillway would have to be sized to pass the difference in runoff volume between present capacity and the volume for a Spillway

| Cesign Flood. The spillway Design Flood, 50F, is that flood discharge,

, cegardless of oth.er designation or method of ccmputation, which is used to develop the hydrologic and hydraulic design of a spillway and dam.

' Other possible remedial measures would be to raise the existing dam (about 15 feet) to contain the PMF or remove the dam completely. ,

1 Since Harriman Dam can safely pass a ficed that is about equivalent to

> a maximum regional event, wnich is a rare event (see Sections 2.2.0 and 4.5), it is recommended that continued operation of the Yankee Rcwe Plant be allowed provided that the licensee initiate a program of analysis, | design and installation or construction of engineered mitigation measures. Such activities shculo be scheduled for completion in coordination with other influential decisions affecting the olant and the dams; i.e., seismic effects, but in any event, to be comcleted by January 1, 1334

.

- 33 -

,

i

,

~ .- . . . . . _ . . - - . . . . . _ . , _.m. , -. ~ - . , . . - . , . . , . . _m_. _ _ . - - ._ - . 4._ . , . ,

. . . . ,

1 7. References

1. U.S. Geological Survey Summary, 1975, "1974 Water Resources Data for Massachusetts, New Hampshire, and Rhode Island," U.S. Dept. Interior, Boston, MA., p. 187.

2. Healy, A., 1965, Charlemont, Mass., Frontier Village and Hilltown, Published bi the Town of Charlemont.

3. American National Standards Institute (ANSI) Standard N170-1976, " Standards for Cetermining Design Basis Flooding at Power Reactor Sites."

4. U.S. Army Corps of Engineers Hydrologic Engineering Center, September 1978, " Flood Hydrograph Package (HEC-1) Users Manual for Dam Safety Investigations."

5. U.S. Weather Bureau (now U.S. Weather Service, National Oceanic and Atmospheric Administration),1956, Hydrcmeteorological Report No. 33, " Probable Maximum Precipitation East of the 105th Meridian for Areas from 10 to 1000 Square Miles and Durations of 6,12, 24 and 48 hours'."

- 6. U.S. Department of Commerce, National Oceanic and Atmospheric Administration - U.S. Department of the Army Corps of Engineers, Hydrometeorological Report No. 51, June 1978, " Probable Maximum Precipitation Estimates; United States East of the 105th Meridian." i

7. Yankee Atomic Electric Company, January 1980 Craft Report, " Hydrologic Probable Maximum Flood Analysis, Yankee Rowe Nuclear Pcwer Generating Station, Rowe, Massachusetts."

3. Wisler, C.O. , and Bester, E.F. , Texttcok 1957, "Pycroicgy."

9. U.S. Department of the Army, Office of the Chief of Engineers, Engineering Manual EMll10-2-1405, August 1959, " Flood Hydrograph Analysis and Computations."

10. U.S. Depa; tment of Interior, Sureau of Reclamation,1977, " Design of Small Dams."

11. Linsley, R.K. , et. al. Textbook 1958, " Hydrology for Engineers."

12. U.S. Army Corps of Engineers, the Hydrologic Er.gineering Canter, " arch 1967, " Generalized Standard Project Rain-Ficod Critaria, Southern California Coastal Streams."

13. Yankee Atomic Electric Company (YAEC) Report No. YAEC-1!39, July 1977, " Yankee Nuclear Staticn Probable Maximum Flood Analysis."

34 _

' . ."

-- - , . ,.. ,

14. U.S. Department of Agriculture, Agricultural Research Service, University of Minnesota St. Anthony Falls Hydraulic-Laboratory, 1958, " Hydraulics of Closed Conduit Spillways - Parts I througn X."

15. World Meteorological Organization, Operational Hydrology Report No.1, 1973, " Manual for Estimation of Probable Maximum Precipitation."

16. U.S. Depart 5ent of Commerce, Weather Bureau, Technical Paper No. 40, May 1961, " Rainfall Frequency Atlas of the United States."

17. U.S. Depart.T.ent of Ccemerce, National Oceanic and Atmospheric Administration, National Weather Service, NOAA Technical Report NWS 24, February 1980, "A Methodology for Point-to-Area Rainfall Frequency Ratios."

18. Tennessee Valley Authority, " Dam Breachir.g Progran", Novencer 1973. 19. Federal Coordinating Council for Science, Engineering and Technoicgy, " Federal Guidelines for Dam Safety," June 25, 1979.

35 . ,-

. . .

' N .) i _ - " a ;8LE 3.2.1

CHARACTERISTICS OF UPPER CEERFIELD RIVER DAMS Somerset Searsburg Harrinan Sherman

1926 Construction Completed 1913 1922 1924

Drainage Area (squ'are 236 miles) 30 90 184 110 Height (feet) 104 50 215.5 310 Length (feet) 2010 475 1250

Das Crest Elevation - 1521.16 1129.66 USGS (feet) 2146.53 1762.66

Spillway Crest Elevation 1491.66 1103.66 USGS (feet) 2133.58 1749.66

Active Storage at Spillway 4561 Crest (Acre feet) 57345 282.5 103375

Surface Area at Spillway 2050 194 Crest (Acres) 1623 25

O.. Discharge Capacity, 5 ft. 6300 over Spillway Crest (cfs) 4950 5350 15040

Discharge Capacity, 10 ft. 20700 cve r Spillway Crest (cfs) 8930 14390 33520 7.2 Ceneration Capacity (M'4) -- 4 33.6

O %' 14 + : - ,

. - ~~ . - .i - o 0 0 0 0 0 0 0 0 0 0 0 0 0 8 4 0 0 0 mw 1 *,/ * eo 9, 2, 2, 8, , . ' l l 0, 2, 3, 6, 2 5 0 2 8 rF 6 2 6 2 ' ' ' 2 1 1 , 3 3 5 4 ~ a - i ,. l . . C x - a s 3(LeL L r. O H .

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8'". 4 . - - , . .3...,-., H S.s ,.u.C . m . . r r. t. L |!o. NA 1-21; Storm Center:Elka Park,ft.Y.; Oct. 4-6, 1932

s MAXIMUM AVE R AGE DEPTH OF RAINFALL IN INCHES Area in Sq. Mi. Duration of Rainfall in Hours | 4. I u I 1A 1 %i to | Mi h8 | 46 | | - Jhx. Station h.7 75 10.0 10.0 10.0 H.5 n.7 n.7 10 h.5 72 9.8 9.6 9.8 n.2 n.5 n$ 100 39 6.3 S.9 91 91 10.1 10.6 10.6 203 38 59 8.6 8.3 8.8 97 10.1 10.1 500 36 5.5 7.S 8.1 8.1 S.S 91 9.1 1,cco 3.3 5.2 72 7.h 7.h 8.1 S.h S.h 2,000 31 h.S 6.6 6.8 6.5 7.h 77 7.7 5,0^.o 2.6 h.1 55 6.0 6.0 . 65 6.9 69 10,C00 2.2 3.5 L.S 5.h 5.h 59 6.3 63 20.C00 19 30 h.1 h.5 h.9 5.3 5.7 57 ' 50,000 1.5 2.h 33 h.1 E.2 h.6 50 50 63,G';O 1.h 2.3 31 39 h.1 h.h h.8 h.8

.

.- No. NA 2-22A; Storm Center: Westfield, Mass.; Aug. 17-20, 1955

INCHES >/. A X D/.U M AVE RAGE DEPTH O? RAIN.7ALL IN ! 0. in Sq. M!.1 Dursti:n Of P.:.im'ctl in Hours jar: I I ' I 6 4 12 _ _t 13 1 24 1 .o 1 35 t c.S 1 60 1 72 I 19.4 19 5 19.3 19.3!19.3 ::::. St. .'d:: 7.) 11.7 14 3, 13.2' ,o I 3 ,, ~o-,.- : > e . - .. -:. ~ ~ --.a,; -a, . :. r ~ n. .# 0 -.- : .). *- - . 7.o- . - ** 3-.: 37 3 ,3: .7 ' . **s 3 ,.y ,. 0.2 -.4- * . o* < . . , -: . as ;, , o, . 3 . - ,. . . . - . I - . . . . . , , , ..,.- . .. .: i, . . , ,, 1.i, -- ., - . ~ . , , . .- .c.~ . .a ... -., -- - ,., ~~ --.~, ' - .:. 32 . . , , - : a . -:.- . . , . -e e.,y ~- 0. o - . . ,c.s- --.- ,e ,, s . 15.4 1,C00 6.2 9.2 10.2 12.4 15.4 15 9 16.2 16.4 ' ' 2,000 j.4 S.0 9.4 11.2 14.0 14.5 14.9 15 2 15.1 j 1*.0s g. 5,c00 -. . o 6.3 7.9 9.5 11.7 12.1 12.6 13.c , 6.5 S.O 9.7 10.0 10.6 10.3 10J ; 10,000 3.1 50 . ) 79 S.3 C.5 5.5 ;D:C *.3 2.1 ?a .6 4.9 6.3 7.6 - e , , e : - : o .,: . ,- -- , . .:- ~ . . . , ,.o f.e ..v ; 5.s ; o ,- 3 -?.- ..s I ! I No. NAl-3; St0rm Center: Paterson, L J.; Sect. 20-24, !c32

. M A :*l.'-iU M AVE A AGE DEPTM OF R.\lN77 LL IN IN CH 7.3 C :catin, of Rair.hil in Hoces ir::a in Sq. Mi. ? I e4 1 ' ': ' 6 l 12 l '8 I 2'. i O I 16 I LA I 40 1 an 24 4 e , '3 . m, - -s s ,at . c, . n 3. , . : . , a . ,, -A.o, -es -s .e c, . t ur .,2 . -- i .i - - -) p.3 -. ,: , ,4 4 3e . --n :: -0., - - ,-; .2 -y.c y .o, - .. --.c .o . A. w 4t . c, 7 , 3 n. - 30.4 200 h.6 33 9.S 10.1 10.1 12.6 15.0 15 2 15 5 15 9 15.9 "4 " - - --. -, 'i "0. 't.,1-- ''.6-- 1' t . 4 >m- 3 si.,. 7.6 3.* o. . '' c. . '- 1,CCO 6.7 7.7 10.6 12.2 12.6 12 7 '3. 2 13 2 2.6 " ' '' ' ' . ~ , :: 7 9 } d4.o .1 e. .. ' 'tO . 4. -- - . , -. 's -- ~,> n..c 3 . ,, e. . a- 4.a - . . a. , , , , '.."-- - , ., . - ; , . ..:. .c :- : . . - , . . - . ;.- .e .a . :- - s : .. .r . , < , ,c e . : .~ , - . . ,- e.s- .. e s ' . , , . i. . , , -+,.*s eu .., . . - u . a. .: * * ** * -, * ^ # ; * ** . . . - s. . ,. J., *% *z , . ,C ,.C s.- ~ . ' - 4..Q. , . , s.,. ~.'J' '| -e- , . '- s.s # * 9 :# ." , C :" . Q, 7 .). . 4 9. Q, ,7 . ,f (u.1s .h.9t 0.' . L , .C, , , I. .'.t , T.- ' } | ' . . *, so)

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.- . r o, L : i s, . ., . c, mn .J .- ' ~ ~ ~ ::o. :A 1-17; Stcra Center: Kinsr.an tiotch, :l.H. ; * ov. 2 * ,1927 M AXI)[UM AVERAGE DEPTH OF R AIN #ALL IN INCHES Area in Sq. Mi, Ouration of Rainfall in Hours l ! 6 u 12 1 19 I 2h I 30 l 16 I L8 l 60 I 10 7.5 10.6 n.7 12.0 12.6 13 7 IL .0 12. 0 100 5.8 83 8.8 9.2 9.5 10.1 10 3 10 3 203 5.7 8.2 8.6 8.8 9.0 10.0 10.2 10.2 500 5.5 79 8.2 83 8.5 90 9.2 92 1 ,0 y; h.S 73 7.7 7.8 S.2 8.8 8.9 S.9 2,000 h.0 6.h 7.0 73 79 5.1 8.2 8.2 5,o:0 2.7 - h.S 6.1 6.7 7.2 7.7 7.9 7.9 10,000 23 -.0 5.5 6.3 6.7 7.0 73 73 20,000 2.0 3.5 h .7 5.; 5.3 6.2 6.h 6.h 50,000 1.6 2.8 3.6 L .1 h.5 L .9 5.1 5.1 60,000 1.h 2.5 33 3.8 h .2 h.6 h.8 L.6

l tio. ::A 1-27; Storm Center: Hector, 1.Y.; Jul. 6-10, 1935 _ , , MA"lMUM AVERAGE CEPTH 07 RAINFALL IN INCHES Area in 5 9. Mi. Duration of Rainf.111 in Hours 6 | 22 | 18 2h I 30 1 36 I h3 I 60 1 72 I 90 | 10 52 10.2 n.h u.3 22 .0 13.h 1k.2 Jh.2 2A2 1h.2 20 51 97 n.1 11 5 n.6 12 9 13 9 13 9 EO %1 100 E9 8.6 10.1 10 5 10 7 n.5 13 0 13 1 13.h 13.6 220 47 8.0 96 10.0 10 3 10 9 12 5 22.6 '2 9 13 2 "4 12.0 12.h 500 h.3 73 3.S 93 95 9.3 "8 1,000 h.0 0.7 S.2 8.6 8.8 90 10.6 10.8 H .1 H.5 2 0C0 35 6.0 73 76 S .O S.2 93 95 10.0 10.h 6.E 6.6 6.3 77 S.2 S. S.7 5,000 h.S 59 - - _ -. 5- 2 7,' - - . c ..i; 10, c,.,0.. 2.- 27 3., . o- 2., 7 ..ie _7. f .0 t.c 72 20,000 13 2.6 32 37 h.1 5 51 5.6 59 6.2 30,000 0.9 19 2.h 29 3.h 33 h.3 h.8 52 5.5 36,500 07 1.h 19 2.h ?.9 33 3.S h.3 h.8 51

*:o.1A 2-2; S:cr, Canter: Barre, " ass; Se;:t. 17-22, 1938 MAXIMUM AVIRAGE DEPTH CF RAINFALL IN INCHES Curation of C.nin Tall in Hours i ' /.c:a in Sq. Mi.! ,>I | | 4 i 33 t ^h I 20 i 76 i ES I 60 I 72 I 96 l '.' 0 1 I I _ > 15.0 | 15.5 f'6.9 ;17.1 ' 10 | 6.h 5.2 9.6 |n.3 '.0.2 13.2 !1h.3 . '.6.3 100 5.0 6.3 83 9.5 10.h 11.h '30. 1h.0 '5.1 16.5 16.1 16.h . 200 h.6 63 7.8 90 9.3 10.9 12.h 13.h 1.h . S 12.6 1h .2 15.5 15.7- 3CO h.1 5.6 7.1 8.3 9.0 10.2 11.6 , 1000 5.1 6.6 7.7 8.h 9.5 n.0 12.0 13.3 'h.6. 15.0 i 37 1h.2 ' 2^00 33 h.6 6.0 7.2 7.S 9.0 10.h n.3 13 2 13 .S 2.7 39 5.1 63 6.9 8 ,2 95 10 3 12.0 12.b 12.0 ' P 77 ,5'CO c 46 ;' i . 0. , -t. '6.g-. i, '. 1 . -; - ! 7 . ,, ,1. ;a u', . t. , v 6 .,,..f ,--.4 , _c. _ r 3 , - , , . , - - ,. . . . . , , _. ! , , ' . . 3 y, .e e..J< ~.3 '.-.s , .e.)- u. :.4 ! ) - . _.; a.- :.) t . ~ -) ''s.3 , , , - - -r . . . . . - - '.9. . .. 9 L.c .; . c O."J ..) I .4 | ?..s j . i!. -. d . ') 3.4 -' ' ' !a; f .5 .- .- ;--- -.9 .' . C, s' . ,? ,1 . " 8. . .',,P.'-? . C. . ,0 ~ 0..>' .

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TABLE 3.3.2(Con't) . No. CP.9-23; Storm Center: Fort Alleghany, Pa.; Jul. 17-18, 1942 "Ste thport' MAXIMUM AVE R AGE DEPTH OF R AIN FALL IN INCHIS Ar-a in Sq. Mi. Duration of Rsinfsli in Hours i ! 6 12 18 I 21. l | I l J 2ax. station 30.7 34.3 35.5 35 5 1 29.3 32.0 33.3 34.2 26.4 22.6 3C.5 31.0 5 ' 10 24.7 26.7 25.7 29.2 20 22.3 ^4.3 26.3 27.4 50 _ 2~, . l' 24.6 ', 9. 7 21.9 , - , , ,u v- .A..,, -1. . , ~ - . . - s.... 200 13.1 16.3 19.3 19.9 500 9.1 13.2 15.7 16.3 1,020 6.4 10.3 12.6 13.3 2,000 39 7.2 9.2 10.2 4,300 2.5 4.6 6.1 7.1 ..- - . --- -. . .- - - - _ - - ._ .- - - -

v i

I I 1AHir 4.1 * , s * . SENSITIVilY ANALYSIS

IIARRIMLN SPILLWAY z 751 CAPACllYS # l!ARRillAN SPILillAY = 1901 CArACilf ' ~ lTiiidee - ~ ~ hut. 1.1ansee fluC Snyder Coef ficientsE Clark Coef ficientsU Snyiler Coef ficientsU Clark OnefficientsU In les R. in fall (Inches) 11.0 16,0 16.5 18.9N 18.9 21.3 16.0 16.5 18.9 21.3 16.0 Ifi .4 IH.9 21.3 16.0 16.5 1 11 . 9 21.3 ___ _._._. _ - . ._ e r _._ _ - . . . 0 y llWI y OIPVOIR 1571.9 157 1.7 1525.7 to ._ Pyl plev) 15?O.7 1521.6 1521.0 1524.3 1525.7 1526.4 1573.9 IS21.6 1524.4 1525.2 1524.1 1524.9 1525.6 1522.6 1574.5 2# 2.419 2,526 41 2.4'H1 2,462 2,514 rc.! f[ _(1000 c fs) ? .16.1 2.500 2.454 1 547 2.596 2.413 2.44'l ?,474 2,5?? _7.4 3 ) _2, 578 . 13.61 l i n. o f I.iilure . 69.31 611. 6 1 69.33 68,0 61.33 13.0 11.61 09.67 6 11 . 6 / 69.67 69.00 60.0 (1.33 10.33 69.ad , ' 74.61 10,i,6 1:wgif 3. (firs) 1/.11 10.:11 69.61 70.33 69.0 68.33 14.0 17.61 70.67 69. f. / 10.67 70.00 69.0 68.33 75.0 78.33 3.41 ' 0 1.% l.24 1.53 1.29 l.33 2. 4') 7.lH 1.55 1.21 1.51 1.55 1.25 1.29 6.0 1.en 1.59' Dinationoverindhrs) ! 'll.qNI_ H1 ',lHVolR I 1172.4 1196. f. 1191.4 1172.5 1174.1 1170.9 1111.1 1174.0 187!. 9 1132.4 ||69.1 1112.0 1813./! flu. hmt {clev) 1131.6 11]) ._3 1182.5 1174.6 1176.5 2 , 32 9 325 2 , 0 114 2,1f _1 2,7 l y i 1 U" 2,151 2.193 2 .352 7,.06% 2 .O''6 2.183 2.250 ?.117 2.164 2.24n !%A ._!LO. '."Mi ( f 5 ) .. 1 146 1 213 ~ f.6. 31 69.67 65.67 65.33 _17m i,I 66.33 _66.0 _65.6] 65.67 ,65.0 _64a 61 66.67 _66 61 _6 6. ,0 _65 6./ f l i" .!! lid!!"fe_S'f5) .l'f'dH! _13. 6 / ' 1.5.07 69.33 68.67 67.65 15.00 71.67 70. 1? ij"". "8 )l.!. (hr() .6/.33 _70.67 10.00 10.65 69.33 68.67 14 . 15 11.00 10.0 11.00 10.31 1.33 2.47 7.45 2.41 2. 4'? 1.41 2.41 2.41 7. It.' . ) t>ur.ition over to d h ) 7.33 2.43 2.16 3.00 2.82 2.51 3.6/ 2.41 2.45

| l/ flRC flood Study using Adopte.1 Values .

(/ "cn'.i. tivi ty Study for Comparison Purpous 1/ 43% of 24-llour Rainf all in tinrst 6.lkmr Period 4/ 5pillway Capacity Limited to Orifice Control in the Riser - Clev.1414

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TABLE 5.1

; COMPARISON OF OTil[R FLOOD STUDIES TO Tile f4RC FLOOD STUDY

Corps of NOCLEAR REGULA10RY COIN. '"9'"'' C. T.fMIN YANKEE P0uE Lower (IPC Report)12 (FPC Report) (1980 Report) PHF timit 1963 f (1977) (1977)

50f tf RSET RESEPVOIR , Peak Inflow (cfs) 40,000 30 300 33,000 54,489 39,000 55,900 reak Outflow (cfs) 7,000 7.100 7.500 8960 6,600 10.000 Haw. Pool Elev (ft msi) 2143.7 2141.4 2141.9 2145.4 2142.5 2144J Top of Dam (ft mst) 2146.58 Starting Pool Elev. (ft ms1) 2133.58 2133.58 2133.6 2133.6 Sut>Easin Rainf all (24 hr-200 S.H.)I ItRf33 19.5 14.1 18.9U 14.0 2/ 25.1 3/

IIARRifiArt RESERVOIR

Peal Inflow (cfs) 210,600 161,500 149,900 240 ,570 172,100 170,000 Peak Outflow (cfs) 216 300 40,700 37,000 2,5 U ,000 32,100 3R,600 thx. Pool Elev. (ft ms1) 1523.2 1/ 1521.9 1519.2 1525.7 1/ 1522.9 1527* Top of Dam (ft msi) 1521.16 Starting Pool (ft ms1) 1488.96 1491.66 1491.6 1491.6 Sub Basin Rainfall (24 hr-200 5.H.) liR# 33 19.5 14.1 18.9U 14.0 2/ 20.6 3/

Sli[RtW4 RESERVOIR Peak Inflow (cfs) 265,300 74,140 87,300 2,121,600 P6,700 113,000 Peak Outflow (cfs) 241 000 71,000 287,000 2,273,300 312,600 110,000*~ H1x. Pool Elev. (f t ms1) ll3I.66 10 1120.6 1131.7 1174.6 1/ 1132.2 1/ 1135*~ Top of Dam (ft ms1) 1129.66 5 tarting Pool (ft ms1) 1103.66 1103.66 1103.6 1103.6 Sub Basin Rainfall (24 hr-200 5.H.) llRf33 19.5 14.1 18.9U 14.0 2/ 25.1 3/

--I/ Dam Assumed to f all when osertopped by 2.0 feet. 2/- 24 hour average rainf all for 236 square mile drainage area 3/The Corps study was for a spillway design flood, so their rainfall is probably based on the reservoir subbasin drainage area. 1/ fio flow over dams.

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1:e.r sr. ~ -1:==n: P.crerence is :::da to the Cc:.--i. ric='s letter acted 15 hw'~:r 19"i2 ccacer..d.n;g ths c.p-11er.*.1.cs filed h '; v -:rsirsi Txar '|cQ :y for liesa:2 for coc:textei b;(d.ro 1cetric projcet (Co. .''. :23) 2r:cctei on tLe Dcsrflaid River in >* ace-""zet+J m:mi Verz::=:t. The c;plicc :t's pmject coccists of sown dr--s vith .Wact:dc power s:ctia=s located as the fceeld River a::1 c.e storts: dc: =;:zi rescrreir es the f.ast E|rs:::f2 cf ths Dearfield Rivt.:r. fhe pre,%ets e.ro loccted between poi.:sta 11 :iles n:ri 59 ci.lcs of th: Decrfield |tiver a ::::tre=2 of its f.:oction with the Cc:::eeticut tiver. 7.1 m is ets ex1ctirc Pa! rel := et; ;ticc ;:tje,:t en 22 Cctre.-tde:r; River fr:r: its r. ::th to 2.rtferd, CO:=: tir.:t, Cd " '-: 'r:10.r ths :::th = of tb- k-:rfield 71rcr. Tha % crc 1cLd .1inz itr21f 12 ::t r,.r: .r.'.1y ar:1 f : ::: .= cic1 W@ica 13 th:re r.:7 1: f.iertic.- th t 1. ;:.--v s r.::sta cf the river for se',W4os cru decired cr c:.:rcn'.,c.d c.t this ti==. , '3e -ir.:Is of the stre.ctures e.ffceti::c wi;;-tica r:v sctisfc;t. .y sud the project vould not effect ths 1::tercets of scvigt. tics. N refore, cy.cfat te::s end coaillio:=s fsr 1:rzertia: is the 1. ice:re, if iccued, c::o c=t ccs=1dered cecess=.:/ i=ccf :r as the inter-et.s of :::::.ci r.tien cro ec=cerr..d.

- h Sj- Sq -W, I'o-- rir :n t.=:1 Ch':::"... ~3 dt. r r0 eC"' Aid ~T'::1 C*wD c'-- ctrtetur::s tith th: '' --tet r.:A h--i=:n decs hcM rc ciMfic 70 dfce- | a3 7,3q f cod faoes of :r::cr.i. -'.2o Cha . :n d.r r.1 a e. r.s cf rii*sr l p:. opt ,; :1 M :=ot :vi e-s. ficco dische.rp. ":'he cC icC:0 hi.'8 ctadied the :f equec;r of -micti:6 :rO** 4'S of '11 D Of * TTUS*C0 er,3 c.sle-tA a C.cciG2 fix.d cct is censider>i a rar: c cat. 2 T. s cr, ,:c-- 2tt. tics 2 :.:de by :::a Cc po of 4:@2r5 t cM en r: :ct ritc:d a indiente that the h e - c::d .P:er.:::: d=:s v ::.ld ;.st peccath: CorJ:' c;.111vn;y desica flood vith Wllvei,f cap. cities ud he@.: cf 6 es

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4TC/-67 9 Chaim, Tederal hr Cb:::issica 3 Tobru 7 1963 sw pro:r.seen! by the sy)l.iacst. dea m.id pcae '.he c;r111voy design finMCor;utar.icos ha +A-t m g,g anir4 cit 2 2r W Corps' or the Ct**piry 's cr1* aria M *here W be a ree-.M. ios i.e fre::to rd assy i sted vitu toe W ' criteria. . r. s pillyg- *2ne Ccr=1saico q with to z y;w m by the Cor73 af Murs viL1 het t1:~11chent .gon : r4: :*Secign fcc.:ur s of t so of the %or c.racm d &*a w , , , , D:. XJF7 af *h c.Wcc. ties 14 retu.- r:d e4 . , gsg.,e:1,

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@ MIN RCLO:r C. Mi ~'*'f.I,I,- Colorml, Corj2 of A-inters Aseic*.cnt W .cr of C1ri.1 */orka for Sc..tcrn D171ricca

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::1 I=d . C 0'4 (15 c:7 62) '' - OUBJC:T: C;w E:, land Pcv:r Comp ny, Projc:t re. 2323 U. S. Arq Ecgr Div, Noir Miami, Walthas, Mass. 30 Jann:ry 1963

To Chief of E= ineers, ATTI: E:QCd-3P, DA, Wachirstos, D. C. ; 1. Tbs applicatics of th.e ::= &;.Ir. d Favor Cc-p:q (t?,PCO) of Corton, Eass :hucatta to ths Tede.m1 Pouer Cc =iscios fcr a licenes for the con:trc:ted tytiroslectric project (:'s. 2323) 1 cated on th.a Occrfiold E17er is rasecchusetta and Tc.~ent tecether with se;plo- mantary data enh itted with yocr lotter of ' Jacanry 1953, has beca revieued and tha folicvin;; repcrt is setaitted herr.:ith.

2. Proic-t, - The projcet cen-ists of c ven dt:s with hydre- cic: trio pc.:= st tions Icected en ths Occrfield circr b:t.*cen p:ints 11 niles are 59 miles upctre:a of its je~ tica with the cen.v.:tiess Ri v cnd or.: das and rccervei.r es the "crt Ersach of the Deerfield P.tver usad to regulate flo::s. The scven de=s with p:Ner statices crer Deerfield No. 2 near Ccavay and Shelbur.1e, l' css. with three generating units totalling h,800 Ed. Deerfield No. 3 near Shelburne and hekland, thss. with three rencrating units totcIling h,SCO rd.

Occrfield '*s. L n:nr D.elh:r.o and Cxt:1:nd, '' :s. with three cencr tine units tctcilinE h,500 ra.

.'ccrfield Co. $ ncer V:=m ind 71c~ises ?h::. vith three gcn:r-ting unite tet:11Lre 15,0':0 CW. Sherren near I!ccroe, E :s. with eno Scacratirc ucit of 1,200 Ed. Eccri in nect Whitinch.m_ e.nd Vilnin, ten, Vt., with

| throo cencr:tir; units tottiling 33,600 Cr!. Sears %:rg near Secr= berg, W.n::st with ons cencratirg unit of h,000 Cd. Thcee s: Ten powcr :tatiene centnis a totc1 of 17 tydroelects.c c ncretirg; c its rith a cochin:d ccpt:ity of ih,000 I'd. Cno of tus dr.:s (E rrir r.) cleo prc:idca a ct:r:co rec =rcir to rc ;n1atc river f1c:a cad cr.2 (Sr:re-t) pre-ides cter:ce ca.ly eith no 1ydeccle:tric Ecn=tirg; fc ei'.i- tice. ILo re:-inire c:co cre uccd fcr pcr.d: o c 17 50 thit.t:tcr ces is | . | csec tic.117 run of rirer fic:r.

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1 C. n l (15 ~:v 62) ^=d I d 3 Jc==ry 1963 f.'J J:.07: f.cw Cs, leaf Pc.t= Cc pc y, Projcat b. 2323 3. F.ffect of Pro. feet es TIced 71r re. - s. Of the eight IIJCO da=s on the Deerflold P.1ver ar;$ its East drarch, three are considered major es.rth stnetures. Two cf t!nsa da s ' h:ve a cic ificant effe:t on zed.::1rq necd ncss. Octercot dts, le ated in tha cpper portien of the Dee:flold River, ocntrols the runoff frca ~C - equers ciles of drein cs arca ta=i cente. ins a ur:bla c:pecity of $7,300 re-fcet er al ost 36 it.:hes of ru..stf. T.:rrir. n de s, ic:sted de::=- ' stroca of Se.:r st des has a cat dreinage arca of 15L equ rs =11 s cad centeins n6,0Co c:re-feet of uc:ble stcrsde WJ.ch is epivaler:t to a.bact 1h in:has of run:ff. C.ct.- :n d:n, a ren of it ter plcnt is a hich c:.rth dca rd is Ic:sted ebc.:t t o ciles d:.:n:treca of 2:rrican d::s. b. C:: rcet Eac:.: :ir is a ctcrece recer eir t.=d in Ec .- 21 la dre11 dcun during tho s: .:::, fc11 cr.d virter ::r.ths to cc.. :::t the n-ture.1 river now. t'ha rece:veir refills du.M.ng tha cpring enew m:1.t 634c:n. ..~rriE:n" R06crYOir is 8 stcrag9 r0&crvcir L'hich alc3 c0ntcias a ponctock for power develo;x:e=t. The reservoir drew dovn and filling in Cenorcl follows the sr..s pcttern as Sc creet Kascrvoir. Tha n-

' meltinc dcas ca the Deerfield River cre run of the river plants with no typrcticble stcraca. e. During the Frnh 1936 fica!, both Con: rect sr.d E:rrie:s der.s etered ele::t the catire :tcra run:ff. Durir; ths T.;ptc-it: 1936 ficed, th: reccid ficed in this crea, Tcc:re:t de: ctc.~_d c.1 : t ths sr. tire ir.Cev cnd rede:cd the cc. ;uted pe:.k ir.fic.i cf 7,f:0 cfc to a ditch..rco cf cheut 1, COO cfs. t.t D.r.-1=_n de: , the cc pated pe ck in- fle:r cf Lh,h00 cfs vas rch:cd to c. .::t 15,000 cre. d. So cerset and E:rric J1 dens sto concidered c:jor certh ctructures cnd both hcTe toen decigned to pass a .jor fleed. Foucraing the Aurcet 1955 nood in c uth:m scv Wisod, the Tr.::: cc recy pce- | Ter.r.:d studies to deter =ine ths cdcqur:7 of crictin; cpillucys et cli ' dc=s ca the Occrfield River. Tho deci;n etc.s veo patter:rd cfter the | Accuct 1955 ctc=, w*tich et its ccetcr r.::.: wcetticid, !':ccc:h:c:tts, | preda:cd IS.2 in:hes of reinfell in h3 h::re. The nr.:ff f.~: the ! decign etern is lh in:bce. U." t hydre..r phc ucre <*(velep

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' 1 NG (15 ::v 62) 2nd I.-d 33 J:= .ry 1963 SUEJECT: |Lnt tr.: lard h:ricri Cocpany, Projc:t 15. 2323 elevatico U29.66 foot, m.,1 prd to sair.rge the spinw:y dic: hat e charnal. | f.o major altarations era ' planned for the rue.:ining d=S.

f. fhs'C:s Eq lcad Livicies h.ss b211t c:7eral flood centrol dsxs ' in the Connecticut Eiver hacin just certh ced couth of th Docefield Myer . Be core rccc3 re:Orreirs hcvs been de:ica:d to pacs ths la*.est Ccrps e-illecy doci;s Cecd with five fc- t of fraob::rd. 50 s 5 D d es i built prior to 1955 do c:t havs edeqc:td epille:y cere:ity to paes a pinusy de:1;s Good cc:puted ftcs tha latort crite-ia. A ginv 7 do- ', cica flood was ec=putcd far Sc .tr:04, T.ar71.0 3 c d Sier n d=a .^n:2 d:ta ' us:d to d: rive the r :est cilley decica fleeds at D11 T.::strin Dc en the Qct Piver ced Littic'-d.no 0:2 cs P.2 F.iddlo Cr:1.05, s'0 tficld T.ver. R.is crM2 ir.dic ted C.st fca rc:t dcs c=ld p::s ths c '11vey decica flood rith Obcut t.a fcet of ft::t::rd but re'diticn:1 t;ine:7 ccpc:ity voald be rcquired et both ii rrir.:n and P :".rn dcas.

s At Et.rrien dsa, if additional cpinucy ecperity were not . g. provid-d,to -nerle ,:nt the limited especity of thz esisting cornin;; gle 7, the des vi 'e to be rair~d an eddition:1 13 foot me.9 3 then the pre =ect p. in c:Y.cr to ctcre the as:ces volu=s of renOff. . h. .it' Cer=.:n de=, the additien-1 cpillucy ccpc.:ity required to pa ss the 'ginvey dt.cign riced socid be et le::t d:chle the preposed e:pecity ced cc:.ld be evcn crc:tcr if ediitional epinucy cepecity were provided ct Escri.r. .s dem. Os fcuc.:in , tablo c.,:-. :ca the ree:lts derived frc: tLs ?cuct Coc.p r.y Ottiic s c .d t'4o C:q,3 critc-is fcr So . rrot, l'.:rr1:. :' c=d 2: ::1':n dt . . '

' CN r .-i Tcn R --rc-t 3 s -F- d e-7 D s - - Ccrp s Fcter Co. Cc pa Po.rce Co. Ccrps Perer Co. Dc e-ript.'. sn Oritaria Criteria Crite-ia Critch a Criteria Criteria l | 'Jrtir.:co Area - eq. c1. 30.0 30.0 15h nct 15L cet 52 net 52 net

DeciCo C h-m | 13 .2 05.1 19 .2 | Fr.infc11-irche s 05.1 13 .2 03.6

Ocrign Stc:s Ru .:ff-ir.:hs s 02.h lb.0 15 .1 1h.0 22.h 'h.0

1 : Ect Peak Ir'lca ' - cfs 55J03 21,CCO 159,000 77,000. SS,003 32,503 Tetal Peck In- fleu - efa 55,e00 21,003 170,0~:0 E0,0:'D H3,000 63,C -O ' I l t

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30 Jarnary 1%) NiDCw (15 Eav 67) 2rd lad 9.3J!CT: New Ec;1and Power Ccapacy, Project No. 2323

Cable contimuod) Sossrest &m F..rriren the Shr~ sn Das Ccips Power Co. Cerps Pcwcr Co. Ccrps Power Co. Mr riotics Crite-ia Crite.t crite-ia Criteria Cri* -M a Criteria ?cak Cutflow - efs 10,500 5,700 33,600 36,000 no, xrA 61,500

r.a11. .a Voo1 stcc, 21LL.7 21h2.68 1,5071 1513.L6 1,1352 1125.L6

Four Co:pecy - Propocad fop of Cass 71h6.58 1$18.66 1129.66

1. It is recognized that the dc4 flood selected by the Pwer Cot;try is a rsre event a:d win provide a see.:h higher degree of prete - tion c;cinct failure than the preecnt de:ics. So :rcut data cas pcca the ' spillway design flood with two feet of fredcard and is concidered eatie- fs:tery. Ferri =en dam, with a fixed rpillv:y ccpt:ity of eboct 38,000 ' efs weald be vulner:ble to a flood cpprocching the ir.:snitude cf a Ccrps epillv:y desicn flood. OL-N ecr"_1ticas cecur at :: herr. n des. .j . Inc;ection of the rc= ining five de .s indicetes .th:t thc;r t.re run of river pl nts with no appreciabla etarecs. Os ic ccr de _icn | criteria used for thece dass is resco=ble sic:e fcilure of ccy of tbca chould not releans the trezcadons volu :s of vctcr required to c uce a catastrcphe.

h. Effect of Proje-t ep T-vir-tic . - 2:re is en erieting Ted: c.1 ncvicction prejcet en the Centu:ticut 1.iver fres its r.::th to Pertfc4 Cc=.;ticut, 65 r.iles balev the c uth of ths Dccrfic1d River. Tne Decrfield Tdver itself is not carrcatly uccd for ec .::::1rl nevigctica, nor is thero eny indicatico that improver.: .te cf the river for scri- Catica ces dcci. red er warrentud at t',is ti==. , 1 I 5. Cel':.rd.e . - It is cc..:1uded t!.:t t'.s tr.to eric'ics etc c;s dr.cc, S.an:rsct sc: Cerriren, h:ve a cictificent effcet in Nduric; ficed fic.:e. F.srric n cad Chctre.n dans, ca d.ifid by prep::ls cf th: Ft.:ct Cocpcay, vill be t:fe accinct fcilr_-e in a 13.rco floed. E:v:ver, th:ta two hic 5 certh d::s have epilivrys which vill n:t pecc a Corps c-111v y decics flood, even s.fter propoccd e:diflecticce. La p ojc:t vc:14 c:t

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