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Home My WebLink About2011-09-20 Planning Board Supplemental Materials (3) Eggleston Environmental August24,2011 NorthAndoverPlanningBoard 1600OsgoodStreet NorthAndover, MA01845 Attn:JudyTymon,TownPlanner RE:StormwaterManagementReview 1780OsgoodStreet DearMs. TymonandBoardMembers: Peryourrequest,IhavereviewedtheMay16,2011SitePlan(revisedthrough8/5/11) andJuly19,2011StormwaterManagementReportpreparedbyLJREngineeringforthe proposedmodificationsattheJ.Tropeano,Inc.propertyat1780OsgoodStreet. ItismyunderstandingthataNoticeofIntent(NOI)applicationfortheprojecthasbeen filedconcurrentlywiththeConservationCommission,andthatmyreviewisintendedto assistboththePlanningBoardandtheConservationCommissionintheirrespective reviewsoftheproject.Myprimaryfocusinthisreviewisthereforeontheproject’s compliancewiththeTownofNorthAndover’szoningrequirementsforSitePlan Review,theMassachusettsWetlandsProtectionActRegulations(310CMR10.0),and theNorthAndoverWetlandsProtectionBylaw(Ch.178)andRegulations,specifically withrespecttodrainageandstormwatermanagement. Theprojectsiteisanexistingcontractor’sstoragefacilityonaheavilydisturbedlot,with wetlandstotheeastandtheMBTAandtheMerrimackRivertothewest.Drainage appearstobeinawesterlydirection,towardtheriver.Theproposedprojectentailsthe additionofasmallporchrooftothefrontofthebuilding,anda50’x60’footgarage addition,withassociatedgrading,tothesideoftheexistingbuilding.Roofrunofffrom bothadditionswouldbedirectedtonewsubsurfaceinfiltration systems. Mycommentsareoutlinedbelow: 1.Theproposedinfiltrationsystemfortheporchadditionisdesignedtocaptureand infiltraterunoffforstormeventsuptoandincludingthe100-yrdesignstorm, thereforeitshouldnotgenerateanyexcessrunoff.Whileitislocatedwithin50ft ofthewetland,Ibelievethelocationisjustifiedbythefactthatitisinfiltrating cleanroofrunofffromanareain similarproximitytothewetland. 2.Theinfiltrationsystemfortheproposedgarageadditionappearstobeundersized. Thedesigncalculationscallfor12CultecC-100unitstostoretherunofffromthe 10-yrdesignstorm,andtheplansshowonly6unitsinthatsystem.Additional analysisisneededtoevaluatetheimpactoftheexcessrunoffgeneratedbylarger 32OldFramingham RdUnit29SudburyMA01776tel508.259.1137fax866.820.7840 1780OsgoodStreet, TechnicalReview2 August24,2011 storms,e.g.100-yrfrequency,fromtheproposedadditionandtheassociated grading. 3.Theproposedprojectentailsfillwithinthe100-yrfloodplain/floodplaindistrict.A floodplainreplicationareaisshownontheplan,howevernocompensatoryflood storagecalculationswereprovidedinthematerialsIreviewed.Inaddition,the stormwaterreportappearstooverlookthefactthatthe100-yrfloodplainisa wetlandresourceareasubjecttoConservationCommissionjurisdiction. 4.Itisnotclearwhytheplancallsfor6-inchesofcrushedstoneinthecompensatory floodstoragearea. 5.Irecommendagainsttheuseoffilterfabricbeneaththeproposedinfiltration systemsduetothepotentialforclogging. 6.Theinfiltrationsystemdetailsindicatethesurfacecovertobeporouspavement.I donotbelievethatporouspavementisproposed(orappropriate)forthis site. 7.Theinfiltrationsystemsshouldbeequippedwithobservationportstofacilitate ongoinginspections. 8.Irecommendtheuseofstrawwattlesorstakedhaybalestosupplementthe siltationfenceerosioncontrol. 9.Disturbedareas shouldbere-vegetatedfollowingconstruction. 10.TheO&MPlanshouldaddresslong-termsourcecontrolstobeusedonthe property,includingprotectionofstockpiledmaterials. IappreciatetheopportunitytoassisttheNorthAndoverPlanningBoardand ConservationCommissionwiththereviewofthisproject,andhopethatthisinformation issuitableforyourneeds.Pleasefeelfreetocontactmeifyouortheapplicantshaveany questionsregardingtheissuesaddressedherein. Sincerely, EE GGLESTONNVIRONMENTAL LisaD. Eggleston,P.E. C:JenniferHughes,NorthAndoverConservationCommission