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Home My WebLink About2011-10-04 Planning Board Eggleston Environmental September28,2011 NorthAndoverPlanningBoard 1600OsgoodStreet NorthAndover, MA01845 Attn:JudyTymon,TownPlanner NorthAndoverConservationCommission 1600OsgoodStreet NorthAndover, MA01845 Attn:JenniferHughes,ConservationCoordinator RE:StormwaterManagementReview MerrimackCollege,VolpeCenter Expansion DearMs. TymonandMs.Hughes: Peryourrequest,Ihaveconductedaninitialtechnicalreviewofthesubmissionsfiledin supportofMerrimackCollege’sApplicationforSitePlanApprovalandNoticeofIntent (NOI)fortheproposedVolpeCenter Expansionwithrespecttostormwatermanagement. IncludedinthematerialsIreceivedandreviewedwerethefollowing: August5,2011CoverLetterandSitePlanApprovalApplication,includingFiscal andCommunityImpactStatements NoticeofIntent,VolpeAthleticCenterExpansion,preparedforMerrimack CollegebyVanasseHangenBrustlin,Inc.(VHB),datedAugust12,2011. StormwaterReport,AthleticCenterExpansion,preparedforMerrimackCollege byVanasseHangenBrustlin,Inc.(VHB),datedAugust,2011. SitePlansIssuedforLocalPermitting,VolpeAthleticCenterExpansion,325 TurnpikeSt,SheetsC-1–C-6,L-1,andSV-1,preparedbyVanasseHangen Brustlin,Inc.(VHB),datedAugust5,2011,revisedthroughAugust12,2011. Ialsoconductedabriefsitevisittothepropertytoobserveexistingconditionsand drainagepatterns.Mostrecently,IreceivedandreviewedaSeptember21,2011letterto theConservationCommissionfromJeffDaggatofMerrimackCollege,outliningseveral conceptualdesignalternativesfortheproject. Myprimaryfocusinthisinitialreviewisontheoverallstormwatermanagement approachanddesignconceptsusedintheproject,aswellasitscompliancewiththe TownofNorthAndover’szoningrequirementsforSitePlanReview,theMassachusetts WetlandsProtectionAct(WPA),theNorthAndoverWetlandsBylaw,andthe MassachusettsDepartmentofEnvironmentalProtection(DEP)StormwaterManagement StandardsandRegulations.MycommentsareaimedatassistingboththePlanningBoard andtheConservationCommissionintheirrespectivereviewsoftheproject. 32OldFramingham RdUnit29SudburyMA01776tel508.259.1137fax866.820.7840 VolpeAthleticCenter, TechnicalReview2 September28,2011 TheprojectsiteistheVolpeAthleticComplex,whichoccupiesanapproximately10.7 acreareaoftheMerrimackCollegeCampuslocatedbetweenCullanAvenueandSalem Turnpike.Thesiteincludestheexisting79,000sfbuilding,apavedparkingareatothe westofthebuilding,twoasphalttenniscourtstotheeastofthebuilding,andassociated landscaping.Immediatelytothenorthofthesitearetwovegetatedwetlandsystems. Surfacedrainageonthepropertyisgenerallyinasoutherlydirection,totheexisting closeddrainagesysteminCullanAve.andthroughthatsystemtoadischargelocation withintheTownofAndover.However,someportionoftheexistingbuildingroofis dischargedthroughtwooutfallstothewetlandtothenortheastofthebuilding.Thetwo tenniscourtsandtheareatotheeastofthebuildingalsodrainoverlandtothesame wetland. Theproposedprojectcallsforanapproximately76,000sfexpansionandmodificationof theexistingVolpeCenterbuilding,inconjunctionwithseveralinfrastructure improvements,includinganewparkingareaintheareaoftheexistingtenniscourts,and reconfigurationoftheexistingparkinglottothewestofthebuilding.Asproposed,runoff fromthenewparkingareawouldbetreatedonsiteandredirectedtothecloseddrainage systemonCullanAvenue. Mycommentsareoutlinedbelow: 1.Theproposedprojectisconsideredamixofnewdevelopmentandredevelopment underStandard7oftheDEPStormwaterManagementStandards,sincethesiteis previouslydevelopedbutanetincreaseinimperviousareaisproposed.Allnew imperviousareasonthesitearefullysubjecttotherequirementsofthetenstate standards,andexistingstormwaterdischargesonthesitearesubjecttoStandards 1,7,8,9,and10fully,andStandards2through6tothe“maximumextent practicable”,i.e.reasonableeffortmustbemadetocomplyfullywiththese standardsandtheprojectshouldbeimplementingthehighestpracticablelevelof stormwatermanagement.Aredevelopmentprojectmustalsoimproveexisting conditions.WhiletheproposedprojectisaimedatcomplyingwiththeDEP standardsfortheexpandedbuildingandnewparkingarea,nothingiscurrently beingproposedtobringexistingstormwaterdischargesintocomplianceorto improveexistingconditions. 2.TheApplicantmakesthecasethatdrainagefromtheprojectsiteiscoveredunder aStormwaterMasterPlan,forwhichtheAndoverConservationCommission issuedanOrderofConditionsinOctober,2001,andthatthedetentionbasin(s)to whichtheprojectareadrainshaveadequatecapacity(flow“credits”)toattenuate theprojectedflowrates.ThePlanandtheapprovedOrderofConditions(OOC) fromtheAndoverConservationCommissionwereincludedinthesubmittalbutit isunclearwhetherthebasinswereeverconstructedand,ifsowhethertheywere builtinaccordancewiththeapproveddesignandmaintainedaccordingly.In addition,itappearsfromthismaterialthatthe“wetland/footballfieldbasin”is actuallyabermdesignedtodetainflowwithinthenaturallyoccurringwetland VolpeAthleticCenter, TechnicalReview3 September28,2011 systemtothesouthandwestofthefootballfield.ThecurrentDEPstormwater regulationsprohibittheuseofwetlandresourcesforthispurpose;allofthe stormwaterstandardsincludingpeakrateattenuationneedtobemetpriorto dischargetoawetlandresource. 3.SubcatchmentM-1B-1dischargestothewetlandtothenortheastofthebuilding (Wetland2)throughwhatappearstobetworoofdrainoutlets,aswellasinthe formofoverlandflowinareatotheeastofthebuilding,includingthetennis courts.Inordertomoreaccuratelyassessimpactsonthatwetland,theseareas shouldbemodeledindividuallyandthewetlandtreatedasaseparatedesignpoint. 4.Thebuildingextensioninthesoutheastcorneroftheexistingbuildinghasroof drainsalongtheeasternwallandlookslikeitshouldbeincludedintheExisting ConditionsSubareaM-1B-1,notinM-1B-3Awhichdischargestothesouth. 5.Additionalinformationontheproposedmodificationsandadditionstothe buildingareneededinorderformetobetterunderstandtheroofdrainageareas modeled. Theplansmerely showthefootprintofthebuilding,butitappearsthata numberofexistingroofdrainsarebeingredirected. 6.Thehydrologiccalculationsshouldincludethe1-yearstorm,inaccordancewith theNorthAndoverWetlandsBylaw.Inaddition,impactstoboththerateandthe volumeofdischargeneedtobequantifiedforeachwetlandresource,andflow pathsandcontrolpointsshouldbeshownonthepre-developmentandpost- developmentwatershedmaps. 7.Thethreepipesexitingtheexistingbuildingattheconcreteheadwallonthesouth sideofthebuildingareunlabelled;whatisthesourceofthedischarge? 8.AppendixAcontainsriprapsizingcalculationsforthreeoutfalls;FES-1,FES- Roof-NorthandFES-Roof-South.However,onlytwooutfallsareshownonthe onthedesignplansandbothareunlabeledandonthenorthsideofthebuilding. Inaddition,itisunclearwhatthebasisforthedischargeratesusedinthe calculationsis;theydonotcorrespondtotheHydroCADcalculations. 9.Thedesignplanscallforreplacingtheexistingdrainlinethatextendssouthfrom DMH-2inCullanAve.Asignificantportionoftheflowfromtheproposed projectwillbedischargedtothe15-inchdrainfromCB-1andnotthedrainfrom DMH-2;hasitbeendeterminedthatthisdrainhasadequatecapacityto accommodatetheincreasedflow? 10.Theproposedplanmakesnoefforttooffsetlostrechargeonthesite,onthebasis thatthesoilsarepoor(HSGCandD)andthegroundwatertableishigh,andthat itisconsistentwiththeStormwaterMasterPlanApprovalbytheAndover ConservationCommission.TheAndoverOOCdoesnotprovideanysuchwaiver ofrechargerequirements,exceptforprojectsentailing<2,000sfnetimpervious VolpeAthleticCenter, TechnicalReview4 September28,2011 areawithintheTownofAndover,andIdonotbelieveithasanybearingon wetlandspermittingbytheTownofNorthAndover.StormwaterManagement Standard3doesrequirethatsitescomprisedsolelyofCandDsoilscomplywith therechargerequirement“tothemaximumextentpracticable”,e.g.theapplicant mustmakeallreasonableeffortstomeettheStandard,includingevaluating alternativesthatminimizeimpervioussurfaces.TheGeotechnicalstudy conductedbyMcPhailAssociatesindicatedthatgroundwaterlevelsintheareas studied(tothesouthandwestofthebuilding)rangefrom2to4ftbelowgrade, suggestingthatthereshouldbesomeopportunityforinfiltrationonthesite. Alternatively,Iwouldsuggestthatthecollegemightbeabletoprovide compensatoryrechargeelsewhereonthecampus. 11.IamawarethatMerrimackCollegeandVHBrecentlysubmittedtwoconceptual designalternativesoutlinedinalettertotheConservationCommissiondated September21,2011.Theplansincludeseveraldesignmodificationsaimedat minimizingbufferzoneincursion,shrinkingandrelocatingthenewparkinglot andprovidingLIDelementsintheformofaraingarden.Basedonthe configurationandproposedgradingitdoesnotappearthatanyofthepavedareas onthesitewoulddraintotheraingarden,thereforeIpresumethatitspurpose wouldbetocaptureandrechargeroofrunoffonly.Whilethismayaddressthe requirementtoprovidegroundwaterrechargetothemaximumextentpracticable onthesite,additionaldetailonthesoilsinthatareaandprojectedrecharge volumewouldbeneeded. 12.Thetreatmenttrainfortheproposednewparkinglotiscomprisedofdeepsump catchbasinsandanin-lineStormceptor450itreatmentunit.Thecalculationsusea 75%TSSremovalcreditfortheStormceptorunitbasedontheNJCAT evaluationscitedontheMASTEPwebsite.TheNJCATevaluationdid corroboratea75%TSSremovalratefortheunitinlaboratorystudies;however theirapproved TSSremovalrateforfieldinstallationsis50%. Thisistheremoval ratethatshouldbeusedinthe TSSremovalcalculations. 13.TheexistingcatchbasinsinCullanAvenuearein-lineandinseries,onehasa brokengrate,andinalllikelihoodtheydonothavedeepsumpsoroil/debris hoods. Evenifflowattenuationisprovidedfurtherdownstreaminthesystem,the proposedincreaseintheflowratedischargedthroughthesestormdrainshasthe potentialtomobilizesedimentsaccumulatedinthecatchbasins.Consideration shouldbegiventomovingthecatchbasinsinCullanAvenue(particularlyCB-1 throughwhichmuchoftheproposedflowisdischarged)offlineandupgrading themwithdeepsumpsandoutlethoods. 14.Theproposedplandoesnotcallforanydrainageimprovementsfortheexisting parkingareatothewestofthebuilding,eventhoughtheparkinglotisbeing reconfigured.Itisunclearwhatconditiontheexistingcatchbasinsservingthislot areinandwhethertheyprovideanydegreeofwaterqualitytreatment. VolpeAthleticCenter, TechnicalReview5 September28,2011 15.TheapplicationdoesnotaddressthefactthatthereisanapprovedTotal MaximumDailyLoadallocation(TMDL)forbacteriaintheShawsheenRiver basin,andthattheTownisrequiredthroughitsPhase2NPDESPermittoreduce thedischargeofthesepollutants.Tothemaximumextentpracticable,theproject shouldemploystormwaterBMPsthatareeffectiveataddressingthesepollutants, e.g.throughfiltrationorinfiltration. 16.AsisindicatedintheStormwaterManagementReport,theproposedproject entailsthedisturbanceofmorethanoneacreandwillthereforerequirea ConstructionStormwaterPollutionPreventionPlan(SWPPP)filedunderthe EPA GeneralPermit.IrecommendthattheConstructionSWPPPbepreparedbyorin conjunctionwiththecontractorselectedforprojectconstruction,andthatthe ConservationCommissionandPlanningBoardhaveadequatetimetoprovide inputpriortotheplanbeingfiled. 17.Measurestopreventillicitdischargesfromtheproposedprojectareaddressedin theLong-TermPollutionPreventionPlan.Theyare,however,somewhatgeneric andnotspecifictothesportsfacilityorthenatureoftheoperations.Morespecific snowstorageareasneedtobedesignated,andtheuseofalternativedeicers should bediscussed,particularlyinwetlandbufferareas.AnIllicitDischargeStatement isalsorequiredunderStandard10andhasnotbeensubmitted.Giventhatthe existingbuildingisbeingrehabbedratherthanreplaced,thatsomeportionofthe interiorplumbing(roofdrains)appeartodischargedirectlytothewetland,and thattheShawsheenRiverhasanapprovedTMDLforelevatedlevelsofbacteria largelyattributedtoillicitdischarges,theexistingbuildingshouldbethoroughly dye-testedtoconfirmthattherearenoillicitconnectionstothestormdrain system. IappreciatetheopportunitytoassisttheNorthAndoverPlanningBoardand ConservationCommissionwiththereviewofthisproject,andhopethatthisinformation issuitableforyourneeds.Pleasefeelfreetocontactmeifyouortheapplicantshaveany questionsregardingtheissuesaddressedherein. Sincerely, EE GGLESTONNVIRONMENTAL LisaD. Eggleston,P.E.