HomeMy WebLinkAbout2010-10-05 Stormwater Review SPR Ile
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From: Lisa Eggleston
Sent. Monday, September 20, 2010, 12:28 PM
T o: Tyre n. Jjudy�. John; Morin
C C., rogan@bakenjoy.com, Hughes,, Jennifer
Subject; RE: 351 Willow St, com men ts
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I agree with]Wady -Jbhn's ernall thl'S morning _5ati,5ifaictorily addresses the remalbing Planning Bid issues so they should be
able to,dose. Judy, Ilet me krim if you need a nything written) from me to thils effect, or whether the,emails will 5,ufflice,
]thin - as lb,ng as you get them to me Iby Thursday morii I should Ibe able to review the last few Items for the Cm(Com
as they are completed this week. I agiree that a separate Erosion &Sediment Control Plan is not necessary, but I would
like to,see the revised plains with the idewatering basins, etc. You can juist ernaiii me,a pdf.
Lisa
Usia l01, Eggleston, P L
Eqgf;estoin Funs iroviiii,eintM
55 (Nd Rd
Sudbury, MA 01,776
t6l
fax 8166,,8.20,,7840
From i: Pmoin@town�ofno,,rthandover,.com
'To. john@nevemorin.coni; lisa,@egglllest.oneinvf�ronmiental.ciami
CC: rogan@bakenjoy.coini,;jhughe!5@�tow,iiiofflorthandcvver.,com
Date. Mon, 210 Sep 2.010 11.,21!!27 -0,400
Subject: RE., 351 Willow St. comiments
Lisa,
I don't tNnik the Planning Board will have issues with the changes that John is piroposing, as long ais you don't have any
issues,with It. I thiink.he,hias dernonstrated that he can treat an exIsUng parking lot area that is Wgier than the ne-w area,
with TSS rernovA of 87%. Overall it provides;a net impmvement to the site and treats a large,area that is currently
untreated, I don't think the condition -that he proposed �provide a revised O&M plain ais a condition of approval) would
be objected to by the Board. So let ine know,what you think, Thanks
Judy
From: John [mail o:jobnCcb nevernorin.cornI
Sent: Saturday, September 18, 2010 11:34 A
To: 'visa Eggleston'
Cc: Ty on, Judy; rogan bakenjoy.com; Hughes, Jennifer
Subject: RE. 351 Wi}€4w St. corn ment5
Hi Lisa,
Thank you for the detailed email pursuant to our conversation the other day. Find attached Borne additional information based on
changes in the drainage design based oa your comments. Also attached are the DEP comments which appear to mimic your
comments.
The original:calculations showed that we can storelinffltrate thQ required water gtmiity vo€usne based on the Simple Dynamic
Method using €"of runoff; therefore 1 don't believe there is any need to change the W V by using 'A" depth. Please rote however
that€f you use a A` depth the WQV =U.S"x 0,15 ac = 0.075 ac-En = 0.00625 ac-ft. The proposed szormwater chambers have a
storage capacity of 0,008 ac-ft bellow the oertlet invert of the system so the chaniber system wiii storeftfiltrate the W V based on
f O
x ,
As you pointed out based on the locationlelevation of the proposed parking area it is difficult to infiltrateltreat this area_ We used
an approach of treating a section of the existing parking lot of the same. if not€argnr, size as the proposed impervious surface_
Subcatchement 35,find attached, is 0,29 acres of impervious,the proposed increase in impervious based on the new parking 1cit i5
0.15 acres, therefore by treating the runoff from Subcatchment 3S I believe we have met the intent cf the regulations. You have
requested that we attempt to diroct more flow from CIS I to the i nfEltration chambers and have stated that you w❑i-rid allow us to
model the chambers using ex{iltration at a conservative rate of 2.41 in1hr. Currently we are proposing a 12"dia pipe from existing
CBI to a First Defense unit and then to the infiltration chambers. this 12" pipe is set at the saine invert as the existing 12" pipe
leaving the structure. In ari attempt to direct more runoff to the infiltration chambers we are proposing to increase the sire of the
} pipe to the First Defense unit to an 18"dia page and drop the invert of this pipe so it is 0.1 feet lower than the existing pipe leaving
the structure, based on these changes the ftow to the design paint is still mitigated and we have increased titre flow/volume going to
the lnfiltraticn chambers as follows {increase based on design changes)-
2 Year Storm. 1.32 cfslf}_092 of i 1.67 cfsJO.161 af) 75% increase in vo€uene
• I0 year Storm: I.90 cfslO,I4Oaf (2.36 cfs10,231 of 65 increase in volume
25 Year Storm: 2,21 cfslO.167 of (2.72 cf00,269 of 61% increase in volume
100 Year Storm: 2.70 cfs/0.205 of(3.27 ds/0.323 a5 57%increase in v ltame
The flow rates and volumes above exceed the flows and volumes generated by subcatchment 3S for the same
storm events. In fact the volumes above exceed the volurnes generated by Sub 3S for the same events by more
than doubte.
ree that if we can demonstrate that we can treat an area of existing impervious surface
Based on your comments 1 believe you ag
(parking lot) that is the same size as the proposed impervious area then we have met the intent of the regulations. As you are
aware the existing parE4ing areas have very little treatment. We are proposing Co treat an existing paved surface with an area of 0.29
acres which exceeds,almost by double, our proposed increase in impervious which is 0.I S acres. Thlis area of 019 acres is currency
treated by a catch basin with a minimal sump. 13y routing this flow through the existing catch basin JSS removal of 5%), the First
Defuse unit JSS removal of 35%) and the Infiltration Chambers (TS5 removal of 80 ) you have a TSS removal of 87%(see
calculations attached). Therefore we have shown that we have achieved the requited TSS removal for are area of equal size, in
actuality of larger size, than the area proposed. Also,we are proposing to treat the new impervious with a treatment device with a
TSS removal of approximately 35% - SO%which exceeds the existing treatment currently on site.
e will provide the required DEP checklist with illicit discharge statement and revise the O & M plan to include the existing catch
basics On site.
I believe the above changes to the design and the additional information attached addresses your concerns as wO as DEP's
comments. Before we fna€e,the plaris and resubm€t i wanted to forward this information for your review and approval_ If the
above design changes are acceptable we will modify the site plan accordin&
Z
We are rneeting with the Planning Baird this Tuesday Sept. 2 1 & ineeting,with the Conservation Commission on'Wedl Sept, 23, 1
believe other than the revised design plans the only other iterns that wi.11. need to be Submitted are the Storn'water Checklist, 1114'cit
discharge statement and inodified 0 & M plan. The project is not complicated and a construction sequence was submitted witli the
NQl application so II believe the site plans can serve as the Erosion Control planis. Depending on how detailed you want tile 0& M
phn,we may not,be able to have all that inforniation subinkted and revie�wed prior to the ineotings this,week.
If you,have time to review the,above design changes prior to the naeeting�;this week, find then acceptable and we can iprovide you
with the final revised plans would you be willing to recornmerld to the P[atining Bolard and Conservation Cornmission to close the
hearing&and make one of the conditions in each pleirmit that prior to,any work on site the applicant shall submit.a revised 0 & M,
plan which shall be reviewed and approved by the North Andover Planning Board, Conservation Commission and their consultant, I
would not usually ask this but we appear to be very close in getting this approved and continuing the hearings will cost us an
additional 2 to 3 weeks and our chent was,hoping to build the parking lot this year.
Please give:Me ar call if you have any quiestions.
On,behall'of our client and myself I wouldl like to,thank you for the tin le and effort you have given oil this project.
John M. Morin, P,.E.
THE NEV'E-MORIN GROUP, INC. 447 Boston Street, US ROLIte 1, Topshold,, MA 019831
978,8117.85 8,6 f 1 978.887.3480 w I .nevi-ngr:w,&L-m
..........
From,- Lisa Eggleston (imal Ito:I1sa@eg1g[estonenvi ronmentaLcom]
Sent: Thursday, September 16, 20,10 4301 PM
To- john,@neveinorin.corn
Canal Judy Tymon; rogan@bakenjoy,com; Jennifer Hughes
Subject: RE: 351 W1111ow St., comments
John,
Following up on our dISCUssion on Tuesday, I have finished reviewing the Hydrology Report for the 351 Willow St. project.
Based on that review, and our dj%usslon, rny comments are as,folljows'.,
L, As we discussed, the First Defense units, and hydrodyiniamic separators in geinerall do not meet the 8,0%,TSS irernoval
requirement by themselves - DEP considers them to be primarily suitable for pretreatment or retro-fit installotio,n s,. A.
more reallistic estimate of their removal rate for most:roadway solids (vs., the sillica sand used in the test study') wauld be
35 - 50%. However, since the gradibg on the site 15 such, that the treatment options for the new paved area are himited, I
thin I it does nale sense for you to keep the 11r,1 Defense unit theme, and to demonstrate that you are providing at, least
SO6 TSS removal. for a comparable area, of the existing parking lot(which currer)tly gets no treatment) through, the
second First Defense unit followed by i nf i 11tration of the water quality volume. This, in conj u nction with the proposed O&M
to be Implemented throughout the site, WOUld, provide a net Improvement in tine quallity of runoff from the site.
2, The water quality volume can be based on '/�-Inch of runoff for this site:-while the soils,clearly have,a higher infiltration
rate than is mapped, I don't believe they warrant bumping up to a 1-Inch, water quMlty volume.
3. T he hydrologic analysis adequately demonstrates that the peak flow rates can be attenuated to, pre-development levels,
even without takings into account any eAltration froni,the subsurface Storage system. As,we discussed, your diesiglin
parameter's for the subsurface system are Oustifiiab[y) conservative. I would encourage youni to direct even more of the
existing flow into the system to maxinilze the treatment and recharge Iprovidecl, recognizing the fact,that there may be
tilnes when its capacity is exceeded and allowing for backup/overflow through, the,existing drain lines. I do not believe,
that this,woul.d warrant a moundling analysis,
4. The Korth, i Andover Wetlands Bylaw does, require that tile hydrologic analysis be ruin for the 1-year storm, and that any
alterations to time volume of discharge, be quantified. This is, primari[y to evaluate: Impacts on wetlands resources.
However, since the project does not entail any diversion of`flow from one resource to another and yau have Mready
demonstrated that the irecharge reqUirement will be, met', I do not believe that these additional analyses are needed. ( en
- feel free to chime In, if you thilink otherwise).
5. Short-term, construction related activities should be removed from the O&N plan and put with the Erosion and Sediment
Control Plan/notes., 01n,going, OW should Include c[eaning,of the existing catchbasins,on tihe site. Since they are Rkelyto
have minimal s urrlp capacity, all of the ba,sins should be cleaned out at least once a year,
6.. A completed IDEP StorrnwaterCheckllst, stamped by a PE, is r6quired. Also required, per DEP Standard #10, is a
statement I ridicati ng that you halve Investigated tbe existing drama e systern on,the site and determined tha It there are
no, [11ficlit discharges from the site.,
please fee[free to contact me lif you have any questions.
iis,a D Eir,;g iris ton, P,E
Eggleston IEnyironrnepit�fl
55 ()Id d (""'()a c,�i Rd.
SUdbiury, PIA ID 1776P
b-A 508-259 1137
fax 816,6.82,018,40
Fromm: john;@nevemorin.com
To: lisa@eggl stop nvironmental. m
CC ftyrnon@townol'northanidover com; rogan@ba,ke,njo .com
Subject.- FW: 51 Wiflow, St. Initlail comments
Date: W'edl, 8 Sep 2010 13.14�28 -0,400,
Hi Lisa,
Judy Tyrnon recently forwarded me your Aui,g 20,email which had several initial comirnents,from you regarding the proposed
drainage for the above referenced proilcct, The PlIannIng Board has,given us pertnission to deal directly with you regairding your
technical review of the project. [was unaware that you did not have the Hydrology Report so that is being semi out to you today.
I believe several of your comments will be addressed once you review the drainage analysis but II also chose to respond to your
CoMmellts (s,�ee responsies below in blue).
The Pkanning Board meeting has,beencontinuied until 912 11101,
Once you have had a chance to review the additional inff61rmadon bellow and the drainage calculations Iplease gi:ve,me a call to
di[scuss.
-4 to woirlki n:g with you on this pro iec:L
'Thank you for your timeand we look�forwaii
John, M. Mioriin, P.E.
THE NIEVE-MORIN GROUP, INC. 447 Boston Sweet, t)S Route I, Topsheld,, MA 04983
1) 119,78.8,87.8586 f1l 978.887.34,90
From: Lisa Eggleston [mailto,�:lisaCOegglie5t,oneinivironmerital.ico,mI
Seat: Friday, August 20, 2010 3:43 PM
To. Tymon, Jody; Hughes, Jennifer
Subject. 351 Willow St.. iinitial cornnients
Judy and Jen,
I have taken a prefirninzry look at the 8/6/10 Special Permitappl,icatiOn, packet for 351 Willow St, but need some
additional c1larification/miore info before I can do a complete review, Basedl on the fauthat the proposed new Iparkriing
area is in buffer zon8, 11 believe this Iprojlect is subJect to WPA and the Stormwater Management Standards, and since it
represents a net increase in impervious airea,it reqtflre-s comphame with all of the SW Management Standards for the
new area. However, theire was,no S,W checklist, des[gn cailculations, hydrologic calculations or other required
4
documentation included in the packet—Just the design plans F'he Hydirollogy/Drairiage Analysis is, [)eing sent out taw you;
today.
Looking at those, I can.o f fe r only the fol lowi ng I ni tia 11 comments
As proposed the new parking,area Would drain to a,vortex separator/inlet urilt, and then discharged directly out the
existing olutfall with no further treatment or flow attenuatiOn. Thus,the new area woulld not meet the Standard or thie
Site Plan Review criteria, though the, net of the entire site Might.
l belie%re the project cornplies M,,thi th,eWPA airid the Stoninwater, rnanagernient staindardssinire proposed impenADUS
area is to be treated Iby a First Defense uinit that: provido-,s,greater than 80(1,Xa T55 removal (calcuWJons are in the
H,ydr(,jj,ogy Anaiysis�. When youl review the drainage repoirt you will see that Ote dnairnage systern has been, designed so
that there is Inm in in the rate of Iri.nnnoff leaOng the site, Not ordy are we treating the, propiose,�.J impervious area
bUt we are also provildhig addffiiuna�,, treabneint to existing paved surfaces.
The desigin, does cal[for diverting:flow from a portion of the,existing upgradlent parking area (that tributary to CB-1),
thirough another vortex separator and then inito a subsurface jnfiltratiion�detentlon systerriwith overflow through
the existling discharge pipe. However, by leaving the existing outlet frorn CB-1 at the same Invert as,the diversion
pipe, it Is not clear that the flow will in fact, be d[verted, I would suggest p1luggingi the existing Connection
between SIB-1 and CB-2, and perhaps hard-piping the roof drain discharge through or arOUnd CB-1 to the new
outlet pipe. The charnber system caninat handle the entir flow frarn, CB1 so that Is why the flow has been
diverted. 'We are, not trying to re-direct the entire, fi!bw for CB,1 to the chamber system, we are diverting enoulgh
flow to provide mitigation in the rare of: runoff to the design points studied as, we4 as to provide the required
groundwater re-charge. Once you revlew the drainage c-a[culations if ylou stfll feel then,,Paed to isolate� the roof
runoff firom CB1 we, can take look at that option aiid see how it affeicits, the proposed drainege de sign.
It Is difficult to tell wi thaut more info, but the proposed I nfJ Itration/detention system seerns to have a lot of capad ty
It does have good solls and; adequate depth, to,groundwater, so it should do a good!job of recharging runoff flbw.
If possible, I would suggest movhng the treatment unit closer to, the recharge system and routing the flow from,
CB-2, through it and the iinfilltration system as well, again hard-pipling the roof drainage through or around the
C13, We caninot re-direct the flow from CB2 to the chamber syraern becaiujise ttie existing outlet ftivert of 2 Is
lowertllhani the Net iinveit of the proposed chanibers, W'e cannot lower the chanibeirssincee we are providing the
miinirnuirn 2 foot,separation between the bottom of t1he charnbers and the Esj-wr elllevationi-, We, Illcnoked at
designed two sets of harnber systeml,; at:different ele-vatbans but tine grading of the parkirig lot wr.)Wd not work,
W'e believe the systeaii, as desiginied meets the standards
The outiet cointrol structure for the infiltration system is labeled on the plan as, having two inlets and no, outlet. This
is a drafting error, you will in,,Qte that the seooind iinvert is loweir than the first invert and that w5 the oudet, but they
both do say "Invert In"', Thies ,,mill be revised an the plan.
5. 1 am not familli'ar with the First Defense treatment u.uiniuts, proposed, and donut Iknow how effective they,are, The
MiASTIEP webisite Indicates that there 1,5 very fittIle I in terms of decent 3rd party verification available, so more Info
wouild; be needed I believe the MAS'TEP data that iiis availaUe satf5fie the testing criteria under the Sturmwateir.
Management Standards for proprietiory treaftnient deVices, We perirn]tted a project thirotigh DEP proposing a
StorrnM)toir Unitzind the DEP did not Iliike it so tliey asked us to propose something else, we dhose a First
Defense untt., We sobimitted the revised calculatwons alorrgwid- the MASTEP data on the Unit and DEP vias
satisfied, ff you have any ad&,Um,,,i,a[ technical quiestions regarding the First Defense unit or the testing data
please feel free to contact DaVid Monigeats of Hydro Iriternational at 1-207-321-3736.
An O&M plan for the proposed BMP5 would clearly be needed; I'd also life to, see it lincoarporate additional O&M
(sweeping, cb cleaning, source controls) that can be implemented site-wide to achieve low cost improvernient.
The 0 & M Plan is provided at the re-air of the IHydrohogtn Repo�rt.
As you are aware, I wiH be on vacation until September 71". [Will plan to,touch base when, I return and i0ok at the
project In further dletaiii then.
Lisa D. Egg eston, Ili It:`
Eggles,ton En,virenmental
55 D[id Coach Rd.,
Sudbury, MA 01776
tell 50&25,19A.137
rax' 86,6 820.7840
�,Lwqo�,&!IL N.,gr
Pic-aoi note,the Massachmett$Secretary iof State-'s ufriba has djaiermined thed irmstfisnahs to anci from rMILAIT16,plal aDifice:s and offjomais ana public records.For miove
Wai rnafion please refer lo- hlm,,
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6
CV"lion,, J'l.I
From., John Dohn@nevemodn-com]
Sent, Tuesday, September 21, 21010 "h GA9,AM
To U a Egigle;ston'
c: Tymtnon, Judy: Hughes, Jennifer', rogan,@balsenj�cy.com
subject' RE': Bake l'sli Joy _351 Willow Street South, Illorth Andlovaer,
Ili Lisa„
h do n ou c thindls we^ illi need as [sage as a stoehcpi[e area.as e showed but i wanted to cover our basis, We wi,11 surround the.
stockpille area with sift fence as needed.
Thanks,
John n M. Morin, P.E.
TIt®JE NEVE-IMORIN OROUP, IMC. 40 Bosw:(')rr, Stl-ee , kiS fu minute 1, "Fopstieid, K A 0 1983
[ 97 .887.858 f°[ 978,,80 .3 480 w [ NyyK,C, rnorJ!1,,cQ
From Lisa, Eggleston I[rrr'uallltc:iisa�@eggle5toin inviroii;mental.carp]
Sent: Tuesday, September 21, 20,10 9,37ANT
To: Johnin lMomin
Cc: Judy Ty man; Jennifer Hughes; t,oga,n baluenjcny.c rn;
Subject E: make N .boy A 351 Wiflow Street South,, North Andover
John,,
Theis hooks good. My one thought iis;tNnat it-appears that time soli stockpiille is, up r-Wlent of the exisUng cat hbasin and the
proposed tnfihtration systeirn. If this its the case you will need to see to it that proper protections are in plaice to pirevent
soil from getting into the system,„ and keep the infiltration ;system offline until the soil stockpile is gone.
In answer to your question, t dlo, not ufeed hard copies of the revised plans;.
{ Thanks,
Lisa
i
f usa D. Eggleston, P.E.I
t 1 le ton Environmental
55,, Old o,ir),ch IRd
Sudbury, 'hwI 01 77
tel ' if 8,,2 5 137
�G�a� gi�,[u�stcrneru �tlrout .' !i �"
From, john ruevernorin.corn
To: llisa eggplestone,,nivironrn,eii�tah,comn
„ JTyrn,un� towinicfncrtbiandlc er.cor,ini Jhutlghes@,towruet'norttr,andover, rn,; rogan@bakenjoy.comi
1
Subject: Bake N Joy,- 3�51 Willow,Street South, North Andover
Date: Mon, 20 Sep 2010 16,15:43 -04,00
Hi Lisa,
Please find attached the revised site,plans® the stormwater checkitst and a,revis;ed 0, M plan. You nientiorued that you wanted die
catch,basins added to,the 0 & M and also wanted "'during construction"" activities removed froin the 01& Mi. Sinice tho project is so
srn0i I felt it approprlate to cogribine!the"duiring construction"and "after construction" activities into one plan, I will! remove,it if
you would I i ke., The catch basins are already included in the 0 & K I did how ever add the client naine, Muffin Realty Trust, as the
entity responsible for maintaining the stormwater Structures on site after constructi,on is complete.
The plans have been revised as follows:,
Sheet I-,Add de watering bKasin and soil stockpile area. Inicrease (length of silt.fence down gradient froni soil stockpile area.
Sheet 2:Add dewatering basin andl soil stockpile area. I nicrease length of silt fence dbwn,gradient frorri soi[ stockpile area.
Add exi sti,rkg grad,es, ups[opQ of wetland flags, 12.3-125. Revise C6 I Ilalbel to show a proposed [8" outlet pipe at iGnyeirt
elevation =249,.S'- Correct the [ab,el of outlet control structure to shio�w Inv, Out",
• $heet I. Modify First Defense Unit 0 1 to show II8" Dia Inlet& Outlet
• Sheet 4: Revise i�nforniatiori for reach, D-1. shiown in Schtedule of Drainage StrLictures & Piping,to reflect an 18"'diameter
pipe andl invert of 249.51"- Revise Stormwater Management Area detail to show 11 B" pipe ente�ring,and leaving First Defense
Unit L Add a dewaterdng basin detail,
If'you have any questions please do not,hesitate to contact n,ile.
l may have already asked you this,but do you want me to inail you a full si:ze copy of the plan oince you harve reviewed it?
Thanks,again for your help.
John M. Florin, P.E.
THE NEVE-illORIN GROUP, INC. 447 Boston Street, US, Route 1, Topsfidxt !MIA 0 1983
p 119,78,887.8586, f 1978.887.3480
Pj(-A�rie note the Mass,achusaus Secretary orsi aw's office has deteniiined,11hat must ermia&&to and from municipal offloes and affidwols ai o pubMic:recordb.For niore
inlormatiani please refer to: V&-L�Ljrn
IPI,cqase consider the Kiviifonnient before,ppiryling this eirnail,,
2
From: Jiohn Dohrrn@inevemodin.comil
senile., Saturday, S8ptember 1 , � 010 11� d A
To, "Lisa Eggleston'
C: T rno, n, Judy„ ro an@bakenjoy.comi: Hughes, Jennifer
Subject. RE, 1 Wiflow St comment
ttac�himents: Bake N Joy-Additional Info,pcif
Hi Lisa,
Thank you for time detailed email pursuant,to our conversation the other day. Fi.rmd attached some additional information based on
changes in the drainage design based c n your comments. Also attached are the f EP cornnments which appear to mimnic your
cormnments.
Thee original calculations showed that we can storefbnfiltrate the reg0red water quality volume.Ibased on the Simple Joynanmic
Method using I°" of runioff; therefore li doe,"t believe there is any need to change die WQV by uusinmg, 'A"'depth. Please mute however
that if you use a A" depth dme + " = 0.5"ru 0.I,S ac = 0.075 ac-in = 0,00625 acrft, The proposed storn,�water chambers have a
storage capacity of 0.008 ac-ft below the outlet invert of the sysnenrr so the chamber system will storehinfi�ttrate,the WQV basedon
I/2nrv..
As you pointed out based on the locationfelevation of the proposed parkiing area it is difficult to infltrateftreat this area., We used
an approach of treating a section of the existing parking lot of�the same, if riot larger, size as the proposed irmmperviomus surface,
Subcatchmemt S, find attached, is 0.7 acres of ii,rnperviouus, the proposed increase in impervious Mused on the new parking lot is�
0.15 acres, therefore by treating the runoff from Subcatchment 3S II believe we have met the intent,of the regulations. You have
requested that we attempt to direct more flew from CB II to the infiltration chambers and have stated that you woauid allow us to
remodel the chambers uisieg exfliltration at a conservative rate of 2,4 II in1h:r. Currently we are proposing a l "" dia pipe from existing
CB] to a First Defense unit and then to,the infktratlon chambers, this 17""-pipe ks set at the same invert as the existing, 12° pipe
leaving the structure. In an attempt to direct more ruuncoff to the infiltration c ainbers we are proposing,to increase the size of the
pipe to the:First Defense unit to an I B" diva pipe and drop the invert of thiis pipe so it its _l feet tower than the existing pipe leaving
the:structure. Based on these cJhaung�es the flow to the:design poinit is still imiti aced and we have increased the flow/volume going to
the infiltration chambers as follows(increase based on design,changes),:
f
I7 Year Storing 1,32 cfs/0.092 of(1.67 cf 0,1 I a l5%increase in volume
ifl Year Storm: 1.90 cfsf0e140af(216 cfs10.231 af) 65 increase in vokime
0 5 Year Storm 2.21 cfs1O.167 of( .72 cfs10,269 af) 1 increase in voiume
� 100,Year Storm:2.70 cfsf0,205 af(327 cfs1BA'32 af) 'S7% iincrease in vollunle
The flow rates and mrollmuin res arb,ove exceed the flows and volumes generated by s,u;mlbcuakclhmenl:3S for the sa nne,
stourrrm ewr''enits. In facet the volurnes above exceed the volumes generated bySub 3S for the same events by more
than double.
Based on,your comments i believe you agree that if we can demonstrate that we can treat an area of existing impervious surface
(pariking hoot)that is the same size as the:proposed impervious area then we have met,the intent of the reguuiations. As you are
aware the existing parking areas have very little treatment. We are proposing to treat an existing paved surface with an area of O.2,
acres which exceeds, alrnasr by double, our Iproposed increase in impervicous which is D.115 acres. This area of 029 acres is currently
treated by a catch basin with a minimal suun,p. By routing this,flow through the existing catch basiin (T'SS removal of S ), the First
Defense unit(TSS.rernoval of 35%) and the linfil,tration Chambers (T55 removal of 80%) youi have a TS�S removal of 87% (see
calculations attached). Therefore we have shown that,we have achieved the required T 'S rernoval for an area of equall size", in
actuality of larger"size, than the area proposed, Also, we are proposing to to-cat the new Impervious with a treatrmeumt device with a
TSS,removal of approximately 5%- 5 11 which exceeds time existing treatment currently on site.
We will provide the re eir-ed DEP checklist with illicit dischairge staternient and revise the 0 & M plan to include the existing catc,
basins on sine..
I believe the above changes to the design and the additional information attached addresses your concerns as well as DEP''s
co nmenrts. Before we finalize the plans,and resubmit k wa.nted to forward this information for your review and approval, if the
above design changes are acceptabte we will .modify the site plan accordirmgNy.
1
We are meeting with the Planning Board tblis Tuesday Sept. 21 & meeting with the Conservation Cotni-ni5sion,on Wed Sept. 23. 1
Mieve other than the revised design plans the only rather items that will need to biesubmitted are the Storm,wateir Checklist, Illicit
discharge statement:and modified 0 & M plan, The proiect,is not complicated andl ar constiruction sequence was slubTnitted with die
N01 apphicadon so [ believe the siite plans cart serve as the Erosiiori Control plans. Depending on how detailed you want the,Ci& M
phan we Nnay not be able to have 01 that information submitted and reviewed prior to the ineetings,this week.
If you,have time to review tine above design changes prior to the meetings this week,find them acceptable and we can provide you
with the final revised plans would you be willing to recommend to,the Planning Board and Conservation Conimission to close the
hearings, and make one of the conditions in each permit that Iprior to any work on site the applicant shall] submit a revised 0,& M
plan whicb shall be reviewed and approved by the,North Andover IPllanniiirng Board, Conservation Continis,sion and their con&Ultant. I
would not usually ask this but we appear to be very close iin getting this approved and continuing the hearings wilill cost uis a9l
additJoinal 2 to 3 weeks and our client wa,s hoping to build the parking lot this year.
Plear$e give ine a cafl if you have any quiestions.
On, behalf of our client and myself II would lhke to thank you for the time and effort you have given on this project.
John M. Morin, P.E.
THE NEVE-MORIN GROUP,, INC. 4+7 Bosti::)ii Strreet, US [kouw 1, I'opsfiehl, MA 0198.1,
p, 978,.887.85 8,6 f 19781.8,87.348,11) vy Awwww n eKp -corn
�Fromi: Lisa Eggleston �[mail�ito-.Ii,.5,a,@e,,ggllestonlenviro,nmerit Il.comiI
Sent: Thursday, September 16, 2010 4 IPM
To,:jobn.@nevernorin.com
,Cc Judy Tymon; rcigan@bakeinjoyicorii�; liennifer Hughes
Subject: RE. 354 Willow St. comments,
John,
Follomring tip, on (Air discussion on 'Fuesday, I have finished, reviewing the flydrology Report for the 3511
Willo,w St. proJect. Based on that rt-view,, and our diseussion,, my coynrne�nts are as, fbllows.
1. A,5 we discussed, tine First Defense units, and hydirodyflamic separators in gerierail do not rneet the 810%TSS removal
requirement by themselves -- DEP cansiders them to be, prirnarily sluitabi for pretreatment or retro-fit install(ations. A
more rea listic estimate of their removal rate for imost roadway solids, (vs. the sihica sand used In the test study) would be
35 — 50%. However, since the grading on, the site is such, that the treatment options for the new paved area are hirniiii I
thilink it does makesen.se for you, to keep the First Defense unit there, and to demonstrate that you are proViding at least
80%TSS removal for a, comparable area of the exiisting parking Ilot (which currentliy gets no treatment) through the
second First Defense unit followed by Infiltration of the water quality volume.,This, in conjunction with the proposed O&M
to be Implemented throughout the site, would provide a net Improvement Mn the quality of ruinoff from the site.
2. The,water quality volume can be based on 1/7-Inch off runoff for this site— wbille the 5olls,dearly have a higher Mfiltration
rate than Is (nappedii, I don't betieve they warrant bumping up to a 1-inch water, qu-Mity volume.
-d
3. The hydrologic analy§�� aideq'i-iiately demonstrates that the peak flow rates can be attenuated to pre evelopment levels
even without taii Into account any exi'liltration from the,subsurface storage system., As we,disc.uissed, your design
, I
pa rameters for the SUbsu irface,sY,5t)em are �)ust[H �y a bif ) coin servat ve. I woo lid encourage you to direct even rnore of the
existing flow Into the system to maximize the tii, ent and recharge provided, rer-oignilizing the fact that there may, be
times when its,capacity is exceeded and allowini for baickup/civerflow throughi the exi",.5t[ing draiiin lines. I do not believe
that thils wouldl warrant a, mounding anaJysis.
4. The North Andover Wetlands Bybw'does, require that the hydrologic analysis, be run for the 1-year Storm, andl that any
alterations to the volume of discharge be quantifiled. This is primadly to evailuate impacts on wet�lainds, resource&
However, s[ince the project does not entail any diversion of flow from one resource to another and you have already
demonstrated that the recharge requirement will be met, I do not believe that these additionall.analyses are needed. (Jen
- feel free to chime in If you think otherwise).
5. Short-term, construction related activities should be removed from the O&M plan and put with the Erosion[ and Sediment
Control Plan notes, Ongoing G&M should include cleaning of the exi,5tinig catchbaslins on the site,. Since they are likely to,
have minimal sump capacity, all of the basins should be cleaned out at least once, a year.
6. Acompleted DEIPS for mwater ChL�,cklliststampedl hey aP'El, is, required,, Al5o, i�-�equiired, ptf, DEP Standard #10i, isa
statement Indicating that YOU have investigated the existing dirainage stern on, the site and determined that there are
no i[ficit discharges from the site.
Please feel free to,contact rmne If you have any questions.
LJSa Irk Eggleston, IP El 11
Egglle,sftoin Enviroiftmental
55 ,Dd Coar,.-Jii Rd
Sudbjuiry, MA D1776
t6 51C.18 259 11,137
fax 866 8210,7B40
ornLantaLcorn
Fronn., Johni@bnevernioriin.co(rn
To., hisa@,egglestone,,nviron�i�ental.conii
CC: pmoiil,(�-bt�ownofnorthc��ndover,com; rog,ain@bakenjcry.com
Subject-. FW: 3,51 Willow to iriftlal cornimients
Date. Wed, 8 Sep 20,10 1114:28 -0400
Hi Lisa,
Judy Tymon, recently forwarded me your Aq 20,mail which had several initiall comments frOnli YOU regarding the proposed
drainage for the above referenced projlect. The P[anning Board has given us permission to deal directly with you regarding your
technical review of the project., ] was unaware that you did not have the Hydrology Report so that is being sent twit to you today.
I befieve several of your conaments will be addressed orate you review the drainage analysis but II a,liso chose to respond to your
con iments (see responses below in blue).
The P'lalinfilig Boqrd mooting h a s been continued until 912 1110.
Once you have had a chance to review the additional information below and the drainage calculations,please give me a call to,
discuss.
Than I, you for your time and we look forward to working with you on this project,
,Jlohn M. Morin, P.E.
THE NEVE-MORIN GROUP, INC. 447 Boston Streer., US Rome I, I c�qisheld, PIA W1983
p, 1978,887,0586 f [ 978.8,87 3480 ve � wfl.ie
From: Lisa Eggleston, [rna,iiito,:lliSa@egglesto,nenivkoiimentai.ccvmI
Sent: Friday, August 20, 2010 3.43 PM
To: Tyimt n, Judy; Hugi'4e,5, Jennif0i-
Subject: 351 iflow St. lnitfal comments
Judy and Jeri,
I have taken a pirelh-niiiiiary look at the,8/6/10 Special Permit application packet for 3,51 Willow St, bunt need so,irne
additional c1larification/imore info before I can do comp 4ete review. 1Based on the fact that the proposed! new parking
airea is,in buffer zone,, 1. believe this projectt,is subjec:t to,WPA and the Stormwateir,Management Standards, and since it
represents a net Increase in impervious area, it requires compliance with all of the SW Management Standards,for the
3
new area. However, there was no SW check[ist,des,igji� calculatioirls, hydrologic calculations or other required
documentation included [in the packet—joust throe desjgn, plans. The Hlydro-0ic)gy/L) ainageAnialysis ens being sent mAlto you
today,
Looking at those, 1,can offer only the,following initial,comments:
As proposed the new parking area would drain to,a vortex separator/Inlet unilt, and then discharged direcfly out the
existing ci with no,further treatment or flow attenuation.Thus, the ftlew airea would not meet the Standard or'the
Site Plan Review criteria, though the net of the entire site might.
lI beheve the project coirnplles,with the MIA.and time Stor,'imvlrater management standards, silrice the proposed limpervious
area is to be treated by a Rrst Defense unit that proMes greater than 8,0%,TSS rerr rwal (calictdafions are in the
Hydrdbgy Analysis�., When vo ju.review the drainage report YOU Willi see that the drainage systern has, been desigil so
that thiere is,no iincirease In,the mite of rulnoff leaving the site. Not orfly are we treaUng the propos,ed inn 1perviimis area
but we acre lalllsol providing addftiojnai treatiment to ex" sfirmg �paved sijrfaces.
The design dooi call ror diveiling .flow ftom a portion of the existing up gradient parking area (that tribulary
to l through another vortex separator and then into a stibsurfiacie hi) ltrationMetention system with
overfl-ow throug[L the: existing discharge pipe. TR)wevet, by leaving the existing outlet From CB-I at the
same invert as the diversion pipe,, it is not:clear that the 110 w wi I I in. fact be di vealed. I would s ug gest
plugging the existing connectio(n,betwileen C.B-I and CB-2, anild Perhaps hard-piping the roof,drain
discharge through or around C`B-I to, the new outlet pipe. The chatnl)er cannot handle the en�tire
fic'mp'l from C'B1 so thal irm mAty thic �flow has beeriii divt�rted,, We are not trying to re-direct the l flow
C13A to the ch.,inilber sylitern, %ve are diverting enoi,igh flow to providic n,fitigation ini of,,'runoA11`
tci, the design 1noirits storied as,AvOl as tar pro,vide fl,,i.e re1qLfirCd gFOUndwater recharge ()nce you review
the drai.n e elalcullations ff'.'l still R"el lh,e need,to i�,.,,cflate (lie CB1 we lc,an tak:e a look
at that oji,fion and see how it afTects the prlll drahl.age design,
It is difficult to tell wi(holut more info, laut the proposed infiltratiointion sYstem seems to have a lot of
eapacity. It does have good soils and adequate depth to groundwater, so it should do a go,(,),d job of
recharging runoff flow. If possible, I would suggest moving the treatment unit closer,to 1111e recharge
system and routing the flow ftoni CR-2 through it and,the infiltration system as well., again hard-piping
the roctf drainage through or•around the CH, We cannot re-direct the fliovv, from, CB2 to the, chatnber
ls)Fstern becaiuse the existing oullet invert of C 3, fer than tt.,ie inlet in,),,ert ci,flthe projx)sed ci,mmbers.
A 2 is 1m,'
�Ve Q,,ar,,nt(,A lower the chambers since we are prov 11 1 1 ding the mininfunn 2 tl selmr,ation be[ween, the
botiArml,'i of the chana ibers and the We looked at desig1ted two sets lafeli.,atilber systemis
at different lei evat ions but the grad.iu g,c)f the paa':king h)t %voiald. ,nol. %vork We believe the systeini, as
designed ineets the stMidar'd.s.
The outlict control strucil'ure fin, the infiltration system is, labeled on the plan as .having two inlets and no
OUllet' iS "Ir draffing, ernm%, 'you Wit] note that the seeckrid invert is tomier than the first hnnert and that
is thie, rmlet, burthey,both do say "Irt-vt-;m Tif This mvffl be revised oil the phlr
I am not farniflar with the Hirst Defense treatment units proposed, and don't know how effective they are.The
MIASTEP websilte indicates that there is very little in, termis of clecent 3,,d party verification avalllabte, so more, info
woulld be needed, 1. believe the MA,STEP data thlat is avallaiNe satisfies the tli criteria jujinder the Stormwater
Management Standards for proprietory treatrnent dewlces,, We permitted a project throughi IDEP proposing a
Storimr-eptor Unit and the DEP did not like It son, they asked us to propo5e 5Qnlethlng else, ,we chose a First
Defiense umt. We submlitted the revised calculations lalonq with the MASTEP data ori, the unit and DEP was
satisfied If you have any addfflonial technlrai quelstons, regairding the First Defense unitoar the, tesUingi data
please feel free to contact David Mongeau of Hydro Initeirriattortal at 1.207,321-3736,
.An O&M, pkm I'm- the proposed BMPs, would clearly be needed; I'd uls(') like to, sine it incorporate additionial
O&M (sweeping, eb cleaning, source controls) that can be implemented site-wide to achieve low cost
improvement, The 0 & NM Plan is provided at the rear on lFthe I Pyiclrology fiil
As you are aware, I will be on vacation untill Septernber Ton: I will plain,to touch base when 11 return and look at the
project in further detail then.
2 Year Stoma Event
Bake N .boy - €parking Lot Expansion - Post Dev Rev 9.20.10 Type III 4-hr Rainfall=3. 10"
Prepared by The feve-Morin Group, Inc. Printed 911812010
HydroCADV 9,10 sin 00401 0 2009 F] droGA€] Software Solufions LLC Page "I
Summary for Subcatcbment 3 : Area Flowing To CB1
Runoff - O.95 efs @ 12.03 hers, Volume= 0.069 af, Depth= 2,87"
Runoff by SGS TR- 0 method, UH;--SCS, Time Sparc= O.W-30.00 firs, dt= 0-05 hrs
Type III 24-hr Ralnfall=3.1g"
Area (ac) DID} Description
0_290 98 Pavernent
_290 1 DO-00% 1mpervlaus Area
Tc Lengthy Slope Velocity Capacity Descdpt�on
(min) (feet) Oft) (fuser.).--- gs)
T 0,9 60 0.0160 1.12 Sleet Flow,
Smooths surfaces € = 0_011 P2= .10"
0,7 40 0.0120 0.92 Sheet Flow,
Smooths surfaces n= 0_011 P = .19'
0-3 45 O.0120 2_ 2 Shallow Concentrated Flow,
Paved Irv= 20.3 fps
1.9 145 Total ---
ubcatc elnt S: Area Flowing To CB1
Hydrograph
1 q)'a C€e —Rurwff
Type 111 4-hr
Rainfall=310"
Runoff Area=0.290 a
Runoff Volume=0.069 of
Runoff Depth=2.87"
Flow Length=145'
Tc=1 .9 min
N=9
a
i 2 3 d 5 G. 7 8 9 10 t1 17 13 to 15 16 17 1.5 15 20 21 72 23 24 25 26 27 28 29 30
Time (hours)
Location. Outlet Stormwater Chambers
B D D B
TSS Removal Starting TSS Amount Remaining
B P Rate Load` Removed (E.3x ) Load ( -D)
Exist. Catch % 1.0 OM 0-95
Basin
to
First Defense 4' % 0.95 0,33 0,62
Dia. Unit
0
f-.- Infiltration 0% 0-62 0.49 0. 1
Chambers
Total TSS Removal _ 0.87
Project: 351 Willow Street, North Andover
Prepared By: JMM *Equals remaining load from previous B 1P (E)
Date. 11 /10� which enters the B P