Lake and Watershed Management Plan for Stockbridge Bowl
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........................................... FOR 6 Maple St. Northboro, MA 01532 ........................................... TABLE OF CONTENTS Synopsis 1 Implementation Schedule ~ 2 Summaryof StockbridgeBowl Infonnation 3 Introduction 3 Lycott Diagnostic/Feasibility Study 1991 6 Watershed 6 Hydrologic Budget ; 6 4ake Chemistry 6 4imiting Nutrient 10 Rho~phorusBudget ; 10 ~hosphorus Modeling , 10 Rhytoplankton 10 Macrophytes 13 Eeasibilityand RecommendedManagement Options 13 ReducingInternal PhosphorusLoading 13 Controlling Nuisance Plants 14 Watershed Management.., 15 Engineering Recommendations , """" 15 Mactophytes : , 16 Algae ".""" 21 Sedimentation 23 Oxygen Depletion ~ 24 Fish~ry Features l 25 Rare Species Considerations 26 Permitting Problemsfor Lake Management 27 EventsDuring the Last Half of 1995 31 Interpretation of Findings to Date 32 Hydrologic Loading 32 Limiting Nutrient 33 PhosphorusLoading 34 Macrophytes 39 Algae 41 Sedimentation , 42 Oxygen Depletion , 43 RareFishery Species FeaturesConsiderations : , , 45 Re-Evaluation of Management Options 46 Control of Macrophytes , 46 No Action Alternative ; 46 Drawdown 49 I»yes 49 '$iological Controls , 50 ........................................... -Dredging Approaches 51 Harvesting Approaches 51 Benthic Barriers 52 Chemical Control 55 Control of Algae , 61 No Action Alternative 61 CounteractingAerationPhosphorus SedimentationInactivation ~ , 69 PreventingImproving FisheryOxygen Features Depletion ; 70 RecommendedProtecting Rare Management Species Plan ~ 71 ViableDredgingHarvestingDrawdown Options , Benthic Barriers 73 HerbicidesPhosphorusWatershedAeration Resident Inactivation Education , , ; 75 Detention Systems 76 .Storm Water Management , 76 AdditionalRecommended Information Approach Needs 78 TechnicalReferences Summary , , Appendix A: Annotated Stockbridge Bowl Reference List A-I Appendix B: Reflections on Stockbridge Bowl, July 1995 , ~ B-1 Appendix C: Literature Review of Drawdown Impacts , C-l Appendix D: Template for Dredging Evaluation , ; D-l AppendixE: Glossaryof Aquatic Terms E-l TABLES 1. Morphometricand Hydrologic Data for StockbridgeBowl 5 2. Land Use in the StockbridgeBowl Watershed 7 3. AmiuaI Water Inputsto StockbridgeBowl 8 4. AverageLake ChemistryResults for StockbridgeBowl, 1988-89 9 5. PhosphorusLoad Summariesfor StockbridgeBowl 11 6. Model Predictionsof AveragePhosphorus Concentrations in StockbridgeBowl 12 7. History of Herbicideand AlgaecideTreatments in StockbridgeBowl 19 8. ManagementOptions for Control of rootedAquatic Plants 47 9. CurrentCosts for Available Benthic Barriers 54 10. Susceptibilityof CommonStockbridge Bowl Plant Speciesto Fluridoneand Tric:lopyr 58 11. ManagementOptions for Control of Algae 62 FIGURES 1. Locus Map for StockbridgeBowl 4 2. Relationship between Total Phosphorus, Chlorophyll.a, and Secchi Disk Transparl~ncy 37 .......................................... SYNOPSIS Stockbridge Bowl suffers from an infestation ofEurasianwatermilfoil and occasional algal blooms, causing navigational and recreational impairinentand deterioration of overall habitat quality. ~rumerous reports and correspondencehave been reviewed and summarized in this document. Milfoil has bee:npresent in Stockbridge Bowl for about 50 years and dominant for the last 20 years. Harvesting aD.da slight winter drawdown currently improve recreational utility in some areas, but do not.keep milfoil in check. Internal lake processesare more important influences on the short term water chemistry of Stockbridge Bowl than current watershed inputs, and the milfoil problem is largely independentof water chemistry. The current primary objective of a managementprogram for Stockbridge Bowl is the control of miJfoil, while the secondary objective is the enhancementof overall water quality for both recreational arid habitat purposes. Evaluation of rooted plant management options reveals that viable alternatives formilfi)il control include continued harvesting and greater drawdown facilitated by selective dredging. Greater clrawdown is recommended, at least to 4 ft. and possibly to 8 ft., but must be facilitated by a pipe or :)iphon to bypass four existing pipelines which cross the outlet, deepening of the area between the island and the outlet spillway, and connection of the outlet with deeperlake waters via one or two channels ;aroundthe island. Implementation of drawdown is further complicated by concerns by regulatory agencies regarding possible impacts on two protected snail species in the lake. Recommendationsare made in this report for the alleviation of those concerns. Drawdown provides both expansive and flexible control and is considered the preferred choice for milfoil management in Stockbridge Bowl based on experience elsewhere. Continued harvesting is recommended as a supplementarycontrol technique, primarily to manage growths beyond the drawdown zone. Actual drawdowncarries little operationalcost, but the neededpipe to bypassthe gasand sewerpipelines had previously beenestimated to cost on the orderof$100,000. The dredgingprogram. necessary to facilitate a 5.5 ft. drawdowndepth had beenpreviously estimated to cost approximately$350,000. Drawdownto a depthof 8 ft. maybe possiblewith additionaldredging and possiblypumping, at an added capital cost of at least$150,000. Theseestimates of probablecost mayrequire revisionas part of a dredging feasibility assessment.Additional costsfor permittingand monitoring shouldlbe included. Realizing that this approach is expensive, costs should be shared in an appropriate manner by all interested parties, including lakefront homeowners on the main lake and those along the outlet channel through the Stockbridge Bowl Association, the Town of Stockbridge, the Commonwealth, and oth(:rs, including private and institutional donors. Grants from private foundations and public institutions are vi,ewed as potential sources of funds for this project. A tentative timetable for accomplishing the necessarysteps, including arranging for fuJlding, follows this summary for easy reference. The schedule provides for the continuation of harvesting, which complements the control achievable through drawdown. A new harvesterhas been purchased and th,eannual operating cost is estimated at approximately $35,000 for two summerharvests of 100 acres of mi.lfoil-infested area. It is also recommendedthat a programof detentioncapacity expansion and maintenanc:ebe implemented, centeringon fonner detentionareas along Lily Brook and ShadowBrook. Educationof watershedresidents ~d eventualcontrol of internal phosphorusrecycling are also proposed. StockbridgeBowl ManagementPlan 1 Fugro East, Inc. ................................,........... IMPLEMENTATION SCHEDULE The primary elementsof the implementationschedule are obtaining adequate funds, completingthe necessarysupplementary investigations for designverification and permit applicationpreparation, acquiringthe necessarypermits, and performingthe constructiontasks which will facilitate achievementof managementgoals. Although someoverlap is likely, theseelements would occur in the order listed. Funding is critical to anyproject, and the needto raise over$500,000 will probablycause some attenuation of the projecttimeline. Supplementaryinvestigations and preparationof permit applicationscan commence oncea modestsupply of funding has beengenerated, while actual implementationwill require that virtually all neededfunds be in hand. Given limited windows of opportunityand substantiallead time for many grantsor public funds,the useof suchfunds will requirean approximatelyone year timeframe,assuming an acceptablesuccess rate. Funds from private donorsor institutionsmay be obtainablein a shorter~riod of time, but somenumber of monthsis still expectedas a leadtime. Consequently,funding this project is likely to require at leasta year of effort, andcould require substantiallymore time. The supplementary investigations necessaryto move this project forward (see the Additional Information Needs section of this report) will require some months of time to complete, but are not especially influenced by seasonor administrative constraints. These tasks could therefore be completed within the period offundraising and should not limit project progress. The timeframe for the actual pennitting process depends on the actions to be pennitted, and is not always predictable, as requests for additional information, continuations of hearings, and appeals can extend the process. The most complicated anticipated action, drawdown facilitated by dredging and pipe installation, should require 2 to 3 months to acquire an Order of Conditions from the local Conservation Commission (assuming no appeal at the DEP level), a partly overlapping 4 months to receive the Section 401 Water Quality Certificate (issued by the DEP under authority of Federal Law), a largely overlapping 3 to 4 months to obtain the Section 404 Pennit (issued by the Anny Corps of Engineers), and a partly overlapping 6 months to be granted a Chapter 91 Waterways License (for work in a Great Pond, issued by the DEP). All totalled, it could take as little as 6 months to move through the pennitting process, or as much as 18 months. The actual initiation of these approval processesis often delayed, however, by the MEPA process, under which an Envuonmental Notification Form must be filed for multi-agency review and through which an Environmental Impact Report is often required for a project of this magnitude. This can add over a year to the pennitting timeline, suggesting a possible