Diagnostic / Feasibility Study for the Management Of
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DIAGNOSTIC / FEASIBILITY STUDY FOR THE MANAGEMENT OF BUTTONWOOD POND MEW BEDFORD, MASSACHUSETTS BAYSTATE ENVIRONMENTAL CONSULTANTSM DIAGNOSTIC/FEASIBILITY STUDY FOR THE MANAGEMENT OF BUTTONWOOD POND, NEW BEDFORD, MASSACHUSETTS PREPARED FOR THE CITY OF NEW BEDFORD AND THE MASSACHUSETTS DIVISION OF WATER POLLUTION CONTROL UNDER MGL CHAP. 628 MASSACHUSETTS CLEAN LAKES PROGRAM BY BAYSTATE ENVIRONMENTAL CONSULTANTS, INC. 296 NORTH MAIN STREET EAST LONGMEADOW, MASSACHUSETTS FINAL REPORT AUGUST, 1988 TABLE OF CONTENTS Page Project Summary Part I: Diagnostic Evaluation Introduction Data Collection Methods Lake and Watershed Description and History Lake Description Watershed Description Watershed Geology and Soils Historical Lake and Land Use Limnological Data Base Flow and Water Chemistry Bacteria Storm Water Assessment Sediment Analysis Phytoplankton Macrophytes Zooplankton Macroinvertebrates Fish Comparison with Other Studies Hydrologic Budget Nutrient Budgets Phosphorus Nitrogen Diagnostic Summary Management Recommendations Part 11: Feasibility Assessment Evaluation of Management Options Management Objectives Available Techniques Evaluation of Viable Alternatives Recommended Management Approach Impact of Recommended Management Actions Detention Program Diversion Program Dredging Program Education Program Watershed Management Program Monitoring Program Funding Alternatives Environmental Evaluation Necessary Permits Public Participation Relation to Existing Plans and Projects Feasibility Summary References Appendices A: Information Provided by Members of the New Bedford Municipal Advisory Committee B: Data Generated by the BEC Study C: Conversion Factors and Calculation Sheets D: Environmental Notification Form E: Comments by Interested Parties F: Glossary TABLES Page Buttonwood Pond Diagnostic/Feasibility Study Sampling Stations 8 Characteristics of Buttonwood Pond and its Watershed 14 Values of Monitored Parameters in the Buttonwood Pond System 34 Selected Parameter Ranges for Storm Waters 48 Chemical Characteristics of Buttonwood Pond Sediments 53 Fish Population Data 64 Precipitation for the New Bedford, MA Area 69 Hydrologic Budget for Buttonwood Pond 72 Nutrient Export Coefficients 76 Nutrient Load Generation 77 Nitrogen and Phosphorus Mass Flow 78 Estimated Nutrient Loads from Storm Events 80 Nutrient Loads to Buttonwood Pond Based on Empirical Data 82 Lake Restoration and Management Options 94 Anticipated Changes to Result from Management 114 Elements and Costs Associated with Proposed Detention 120 Elements and Costs Associated with Proposed Diversion 126 Elements and Costs Associated with Proposed Dredging 133 Elements and Costs Associated with Monitoring 138 Potential Funding Sources 139 Permits and Approvals Required 142 Summary of Management Actions 148 . ....- ., I1 Ill I I I 1' I PROJECT SUMMARY Buttonwood Pond and its watershed were investigated and evaluated in 1986 and 1987 by Baystate Environmental Consultants, Inc., on behalf of the City of New Bedford. The study was made possible by funding through the Massachusetts Clean Lakes Program of the Department of Environmental Quality Engineering and the Olmsted Parks Restoration Program of the Department of Environmental Management. The physical, chemical and biological features of the pond were assessed and management recommendations have been prepared. The results of the study indicate that Buttonwood Pond is receiving excessive loads of water, sediment and nutrients associated with storm water runoff generated in the urban watershed. Past sedimentation has filled in approximately one third of the pond, and current nutrient levels support algal blooms and dense growths of macrophytes. Flooding of park lands occurs in response to periods of intense precipitation; the inlet channel to the pond can handle only about 85 cu.m/min (50 cfs) of flow before overtopping, and the storage capacity of Buttonwood Pond is limited by very slight shoreline slopes. Approximately 62% of the phosphorus load to the pond is attributed to a single storm drainage system serving less than 18% of the watershed area. An upstream detention basin has an outlet structure which prevents detention of water during all but the highest possible flows. The Buttonwood Brook system has not been engineered for downstream water quality or flood control. Review of available management options has eliminated many techniques from consideration. Evaluation of the remaining alternatives in light of technical and economic considerations has yielded a recommended management plan incorporating detention, diversion, dredging, and environmental education. The storm water drainage system contributing the majority of the phosphorus load to the pond is to be routed to the southwest corner of the park, along with four minor drainage systems which can be easily tied into the diversion pipe. The upstream detention basin is to be modified to detain water during low flows while passing enough flow during major storms to prevent overtopping and localized flooding. Soft sediment, silt laden sand, and accumulated debris are to be removed from Buttonwood Pond, dried and used within the park. The pond shoreline is to be steepened and stabilized in conjunction with the dredging program. An educational slide show and brochure are to be prepared and presented to watershed residents. The proposed management plan is expected to yield substantial reductions in the loads of phosphorus (68 to 89%) and nitrogen (45 to 74%) to Buttonwood Pond. Considerable in-lake decreases in turbidity (40 to 95%) and plant density (60 to 80%) FIGURES Page Sampling Station Locations 9 Buttonwood Pond Sampling Stations 10 Bathymetric Map 15 Hypsographic Curve 16 Boundary and Topography of the Buttonwood Pond Watershed 19 Land Use in the Buttonwood Pond Watershed 20 Sub-Drainage Basins of the Buttonwood Pond Watershed 22 Soil Types in the Buttonwood Pond Watershed 24 Buttonwood Park: Existing Conditions 30 Buttonwood Park: Master Plan 31 Storm Water Drainage System of the Buttonwood Pond Watershed 46 Soft Sediment Depth and Sediment Sampling Locations 52 Residual Turbidity, Settling Rates, and Bulking Factors 55 Phytoplankton Density 58 Distribution of Aquatic Macrophyte Taxa 60 Density of Bottom Coverage by Aquatic Macrophytes 6 1 Hydrologic Inputs and Outputs 73 Total Nitrogen and Total Phosphorus Inputs 83 Possible Sites for Additional Containment of Storm Water 106 Possible Outlet Structures 119 Proposed Pipeline Pathway for Diversion of Storm Water 124 Work Areas Associated with Proposed Dredging 128 Typical Embankment 129 Haybale Silt Barrier 130 PART l DIAGNOSTIC EVALUATION are also expected. The probability of flooding will be reduced (30 to 50%) as well. The physical features and appearance of Buttonwood Pond will be altered to provide a more hydrologically functional and aesthetically appealing water body. Habitat quality is expected to increase appreciably for most forms of aquatic life, and pond condition will be more appropriate to its desired uses. The proposed project is consistent with the Buttonwood Park Master Plan, which is in the implementation phase. The total anticipated cost of the proposed management plan is $1,455,350, which includes the basic elements described above and a monitoring program for assessment of results and adjustment of management actions. A four-year implementation schedule has been outlined, with detention and diversion options implemented prior to any dredging. Monitoring and education should take place throughout the period. Additional management actions may be desirable (e.g., additional detention capacity provided upstream of Buttonwood Pond), but the proposed project should yield conditions acceptable for the desired uses of Buttonwood Pond and the surrounding park land. INTRODUCTION The establishment of the Massachusetts Clean Lakes Program under Chapter 628 of the Acts of 1981 enabled many municipalities and lake associations to acquire funding for study and restoration of their lakes. As an environmentally aware and concerned community, the City of New Bedford applied for a grant for a Phase I diagnostic/feasibility study of Buttonwood Pond, a highly visible element of Buttonwood Park. After being awarded the grant, the City contracted Baystate Environmental Consultants, Inc. to conduct the study. Concern over the present and future status of Buttonwood Pond and its impact on the impending restoration of Buttonwood Park prompted the request for a study. The water quality impacts of human activities in the Buttonwood Pond watershed were largely unquantified, although it was apparent that the routing of storm water through the Buttonwood Brook system (including Buttonwood Pond) was largely responsible for deteriorating water quality and frequent flooding in the park and adjacent neighborhoods. Mitigation of any current negative influences on the pond and prevention of future degradation of this water resource were desired. Under the Olmsted Parks Restoration Program, administered by the Massachusetts Department of Environmental Management (MDEM), major improvements are to be made in Buttonwood Park. These improvements are intended to provide increased recreational utility in a more aesthetic setting consistent with the park design principles of Frederick Law Olmsted, whose firm was involved with the establishment of Buttonwood Park. A master plan for the park has been developed by the Walker-Kluesing Design Group in conjunction with the MDEM and the City of New Bedford. Restoration work has already