HomeMy WebLinkAbout1997-05-21 Response to Stormwater Review CHRISTIANSEN & SERGI, UNIC.
PROFESSIONAL ENGNEERS AND LAND SUIRVENORS
1,60 SUMMER STREET HAVERHILL, 01830-6318 (5308) 373-031.0 FAX, 372-3960
...............
May 20, 19,97 MAY 491
North Andover Planiiing,Bloar
146 Main Street�
North.Aild over,, M A 0 18 4 5
RE Orchard Bill Road, Lot 12-A,Drainage
In response to the comrnent letter by John Chessic, dated, 4/24/9,7, with respect, to
Drainage, I olfer t1i'le followin
As stated in the Report on Stomiwater Mitigation, dated, AP it 3, 1997, tile
applicant has, designed a systern to mifigate all increase in runoff for the I GO year storm- It
follows them that it will also handle a]I i nerease in run off for the 2 year and 10 year storm
events, It doesn't matter where the.run off conies from, it will niost I ikely come fr m the
site area because the time ofooncentration is so small. If water enters. the leach,area fi-oni
off site,, that still represents a decrease in flow down stream. Therefore, it is,11a necessary
to present a pre and post consauction analysis for the entire drainagre area.
Even individuals with only an elernentaty understanding of hydrology would
understand that the system, we propose will,reduce the volume of rimoff(firom whatever
the source) and a detailed analysis of the total: area surrounding the site:is not needed.
Ven
01fistiansen
CHRISTIANSEN & SERG17 [INC.
PROFESIDNAL 04GNEERS AND LAND SURVEYORS,
160SUMMERStMEJ HAVERAIU, tOkSSACHUstrisoi83o-63i8 (508) 373-0310 FA,'C (5()8) 372!.3961D
June 11, 1997
Town of North Andover
Planning Board
146 Main St .
North Andover, MA 01845,
RE : Chessia Letter of June 5, 1997'
Orchard Hill Road
Industrial Subdivision Site Plan, Parcel I-2a
Dear Board Members :
Much of what Mr. Chessia requests in his letter has been
submitted and other information is not needed or, if provided
would make the proposed �acilities unworkable .
My response to his comments are provided below in the
same order as provided in his letter of June 5, 1997 .
1a) The drainage control facilities are shcwn an the plan.
The drainage calculations were submitted on April 3,
1997 .
The calculations do show mitigation for the 2 , 10 and
100 year storms . I have attached a post drainage sub
area plan . A, pre-drainage sub area is not needed since
all of the site runoff from impervious areas is
discharged to the ground , The change in flow patterns
will obviously be substantially less flow to Orchard
Hill Road.
10) No comment .
1bii) There isn ' t any state or local rule or regulation .or.
rule that requires a 2 - 4 foot separation between
ground water and a leach facility. The Mass DEP is at
present, developing a storm water managevent policy
which only applies to sites within the jurisdiction of
the Wetlands Protection Act . Such policies should not
be arbitrarily applied to sites outside the jurisdiction
of the Wetlands Protection Act before it is adopted by
the DE P and without the benefit of those policies
adopted as a Planning Board rule or regulation .
I suggest that a percolation test be conducted during
construction on the dense soil strata Mr, Chessia
referenced. if found not to conform to the calculations
the leach area can be redesigned .
Plalliaing Board, June 11, 1997
Page
lbiii) Plan is attached.
lei) . The design of the leach area provided is ore .that r
Chessia recently approved at Beechwood Dill . .
IE we were to install an "inlet grate over a catch
: basin with a deep sump and hood with runoff piped to the
: leaching ares93F as suggested r the leach area would be 4
: -Feet further in the ground . Pipes from catch basin
should he 1 'f and have 3 feet of cover and the invert of
. .the pipe should be above the leach area , The bottom of
the leach area would then be at leas. 8 feet blow grade
rather than 4 . 67 feet as proposed and would further
exacerbate the groundwater separation problem that Mr.
Chessia refers to in item lbii. .'A sediment trap Is :
:provided in our. detail . . . . : .
Oil separation can be addressed by using Matasorb in the
.sediment trap during the first year after the pavement
is installed. The :Matasorb will adsorb the o-il and can
-be . replaced as .needed . : .
I ii) . .The Anconsistencies .will be corrected. ,
Yer
l .P li G. Christianse �
P ; I
cc : J Chessia
or
A ! NA GE A REA S
FOR
ORCHARD
A = 10,348 SwF.
PROPOSED '
BUILDING
A = ,800 S.F. `