HomeMy WebLinkAbout2008-12-18 Drainage & Sewer - Anne Bradstreet Early Childhood Center MG_ Marshall Gary LLB
SITE PLANNING € LANDSCAPE DES€GN ENVERONMENFAL € EMN
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To: North Andover DPW ay,d Planning IBwRl
Fnim: Ben Qiir
CC.: Patrick&-dita
Municipal Fl6Iding Cons0ants
Date: November 24,2008
RE;: Profrased Modular School
Beacon Hill 13oulevaril,North An
Drain€aga Analysis
Project Safe. The proposed project site is a wooded area at the northwest corner of the
intersection of Chickering Load and Beacon 1Aill Boulevard. `Phis ground slopes from an
elevation at Chickering Road o€ 194 northerly at 3- % towards #Ire Atkinson School at an
elevation of 182, A cat6 asin on Chicleering Road discharges into a pipe that has a
headwall in the corner of the site near Beacon Hill Boulevard. Although this headwall is
partially blocked water does flaw in a ditch away from the headwall into the site.
Based on the geotechni cal report be]ow the forest mat aTe, glaciofluvial deposits consisting
of silt and fine sand to a depth or 15 r,eet. The groundwater elevation is between 9 and 10
feet below the existing ground. Currently surface water runoff flaws overland to the lawn
area of Atkinson School and extension of Beacon Hill Boulevard. The proposed project
devclopment is over 100 feet fi-orli the identified wetlands.
Proposed Development. It is proposed to construct a one story building approximately
14,000 sf with a craw space 3 feet deep, The total disturbed area is 41,900 sf The project
alto includes a paved play area and a driveway with handicap and visitor parking, The
proposed drainage systern collects the runoff from the existing headwall, drive and
parking, building Toof drains acid pedmeter foundation and discharges into an existing
drain manhole.. An existing 1 " storrn drain eonnem, This manhole with a Manhole fin
Mw;sachuse,tts Avenue.
20 CAB O'I' Fit), STF.,, 100 181,935,1665
WOBURN, I+rfA 01801 WWWAngary_COF11 f. 781.935,0166
November 24,20DS
1v1EM0, F)rainage Analysis— Proposed Modular School Building 11- 4-09 Page
Drainage Calculations
The peak discliargc, ranolf' volumes and TS9 removzl are calculated based on the
ropo ed developnictit. The design storm events are:
Beak 13ischarge
Inches of rains ll in 24 hours:
2 year storm 15„
10 year storm 5.111
100 year storm 7,6"
Area. 41,900 sf
Cocfl:icients ofRunoff- pavement &. roof.98, woods .25 and gra�;a A
Using,the Radmil Method ( =cia) the peals discharges 0 or cubic feet per seeon ) pre
and post &velopment at)-, as follows:
torni Event Pre Develoorgen# w w „ , Yost Development lncrease
yr. 75 cfs 6.3 cfs 5.25 efs
10 yr, 1.83 ef's 9A ci's 6.57 efs
100 yt, 2.25 efs 9.8 Cfs 7.55 efs
As the capacity of the 15" storin drain at a slops of 51A is 14 efs it would appear that it h
adequate capacity for the calculated discharge from the project. There are some drains
from the Alkinwii School c;oruiected to the 15".arid the discharge from the catchbasin in
C.hickerijig Road is unki-io n.
Volume
The design for the storm drainage system utilizes perforated PVC pipe installed with one
root of crushed stone (1 l?") top, bottom and sides with the stogie wrapped in rilter fabric,
The design inteiit is to allow the stormwatcr runoff'in the pipes to leaQb into the sails as
well as store the some of(lie runoff into the voids of the, i iuslied stone. The design hitent
is to red-ties the volume of'runoff to th.e existing 15" pipe,
I'ase 2
i
Novunber 24, 2008
lEMO. Drainage ,Analysis —Proposed Modular School BaiIding 11-24-08 Page 3
The following are tlic calculated volumes (cubic feet) of runoff for the stated storm
events:
Storm Lvcnt Prt�DevelopinerL ry-- Yost Development. increase
2 yr. 3040 cf 9500 cf 5460cf
10 yr. 4500 of 8100 of 3640 cf
100 Yr, 6600 of 11,880 cf 5,280 of
Based on the approximately 420 feet of 12" perforated pipe and crushed stone it is
estimated that the percolation (ass umitng l" iri 30 minutes) plus the storage in the stone
(401/.)) and pipe will equal a total storage capacity of 6380 cf. Which will off-set the
increase in volume evem for the 100 year storni of 5,280.
Notes:
I. regarding the TS total suspended silt) removal, all catchbasins have four foot deep
sumps with hoods and it is proposed that the driveway and pai-Icing be swopt to reduce
suspended silt.
2. During constractioii a combination. of haybales and silt fence will be installed and
maintained on the edges of the development closest to the wetlands. Other measuii--s
will be taken to control s{)iI erosion and sedimentation.
3. While the design approach is based on accepted valises for rainfall events, runoff
coefficients, soil data and Formula this information has not been reviewed by an
Engineer, The approach to all utilities including drainage rind sanitary sewer have
been reviewed with the Town Fngineer. With regards to the drainage design the
building and outside fkilities sine protected from flooding and the impact on the Tovm
system is Mitigated.
• Page 3
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MG
Marshall Gary LL
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SITE PLANNING LAMOSCA?E DESION 3 ENV€RONMENTAL DESIGN
M3
To: F.ugEne l'_Wi11is,Town Enginwr
Firm- Tim Gary
Ct=, Fa trick So ha,?1unicipal 13LiiIding Cons,
Date, December 1,2009
RF., North An(lover Modli1ar Pp-e.-J< c.hool
With IV ip t to yuur November 25t1" letL€.r to the porch Andover Plaililfnol Board (Copy
attached fog•r6erem e) we propose the following:
i, A sanitary sewer maiihole with vehicular access outside the praposed hu;lding -w�II be
Ineluded Ill the LEtlllty dt%ign,
. The present design for the proponed sanitary sewer does appear to be crossing (abOLEE
two feet below) the potential cement asbestos drain. This cr(7$,3ing will be ree amined
and checked again%t field dzaa and depending on fhcC Edcnti>iication of the drain. the
material, location and inverts, the proposed mnitary -,ewer will be revised with the
€ bjective of avoiding this crossing.
3. The existing ditch carrying the 12" storm discharge firo T9 Highway Route 12.5,
111okL:rhig Road will be directed to a I}1• po5�d, shallow, veegetated Swale ovci' 400
feet long extending fi-om the discharge point at Rt. 125 north along the west side of
tlic building, This disium cs should be adequate f6r dissipation of the sia-face. water
runoff. The proposed 12" pipe, dr6n manhoh, and catchbasin on thy; Vast side: of the
proposed buiIdiiig will be dcleled.
4. The €2. storm drain from DM 4 to the existing drain d71aE1hole, w i I I be changed to
5. A€though cle�kl autS are provided for the comers of tlic perEEnctci` dnain, at cleailout wiII'
be piovldcd at the intcrscetion ofthe propmed roof and folindaflon drains,
20 C:A BOT RD, STF_ 100 p. 78 1.93 5_€665
WCI}3 R ,MA01801 f 79€_433,0166
TONNIN OF" NORTH, ANDOVER
DIVISIONN, OF" ]ITTFIFIC,
3811 OSG1001 ST11111 F-F, F
!w,K)[CF1 AN DOVA,:JZ, M A SSACITUSUTS CC�845-2909
F)I R K"TOR
Fax (9,11N) 688-9573)
November 25, 20,08
North Andover Planning Bourd
1600 Osgood St.
North And0VeT
Re: North Andover Modular Pre-K Selm
Dicar Board Members,,
Lhave,rcviewed Aeets L-I through L-7 of plans by Marshall Gary1.1 C dNted Noveinber 3,
D'.),08and drawn. for the North Andover Modular Pre?K School. I oll�r the following comment's,-
I. The sanitary sew errequires a nianhole with vehicular aceess outside! the building, Jbr
maintenance,
I Thesunitary sewer routing appeas to cross what may be an existing cernent a.%be tos,drainpipe
at the southeast corner of the Atkinscm School. If this, is the:case, the sewer sli(yuld he
redirected to avoid this crossing.
3. rll,, 12"'storm froin .Ma Hi ghway Rte 125 flared end at the southern limit o('work shoulid not be
piped into the town systern. A treatment swule can connect the outfall to the inliltration pond to
he built on the south side of the building.
4. '17he 12"storm fry ii DMH 4 to the existin MHshould be: 15" dig;me ter if there is a 15"
diameter pipe out of the existing manbole.
5. There should be some sort of structure/Cleanout at the it teo,;�ction of the,proposed roof and
foundation drains.
Sim Y
1416gp le P� Willis PE
iTZ n Engineer
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