HomeMy WebLinkAbout1986-01-06 Drainage Calculations DEF SUB JOHN CALLAHAN ASSOCIATES
ENGINEERS - ARcHITECTS - PLANNERS
166 K MAIN ST,, ANDOW.:, MASS. 01810 475.06M
ORCHARD HILL COMMERCE PARK
DRAINAGE CALCULATIONS
_Pre-Development Runoff
Use: Empirical Approach Q = Aci �S/A
Total Sate= 5 . 5 Acres
Avg. Slopes = 4%, c 0 . 45
i 2 . 50/Hr. on 25 Yr. Storm
Q = 5 . 5 x 0 . 45 x 2 . 50 5 40/5 . 5
Q = 6. 18 x 1. 49 = 9. 2 cfs .
Post Development Calculations
Increase due to proposed improvements
5 . 5 Acres ; 45 . 7% covered by buildings , paving & walks = 2 . 51 Acres
c = 0. 90 i = 2 . 50
Q = 2 . 51 x 0. 90 x 2 . 50 525/2 . 51
Q = 5 . 65 x 1. 59 = 8. 98 cfs .
Provide storage capacity for 8. 98 cfs , for a 20 min, duration.
Capacity : 8. 98 x 20 x 60 = 10 , 776 cf required,
Provide an area of 4000 s . f. x 2 ' 8" deep
Mote : design storage detention pond with a control outfall
structure allowing small flows to exit a 15" RCP pipe.
This provides for a zero runoff due to the proposed building
and paving improvements, as well as a 45% reduction in flow
from the existing unimproved site .
STATEMENT OF ENVIRONMENTAL IMPACT
at the Orchard Hill Commerce Park
Development , North Andover, MA (Parcel I-2)
The subject Park contains 15 . 2 Acres and is submitted as a single
lot subdivision with an improved cul-de-sac roadway extending
approximately 700 ' into the site . It is anticipated that perhaps
3 or 4 lots will be subsequently divided out of the parcel , this
depending upon the needs of the community' s industrial-commercial
growth.
The site is wooded throughout with mixtures of hardwoods and soft-
woods , many of which will remain outside of buildable areas , To
enforce the developer' s desire to leave as much as possible of the
natural landscaping, an Architectural Barriers Board has been es-
tablished for site development and plan review by the developer
and his architectural-engineering representative.
The Environmental Impact Statement will now follow the guidelines
of Section III B 5 of the Rules and Regulations Governing the Sub-
division of Land, Town of North Andover (1981) .
III B 5 a) Plans : Refer• �to Subdivision Plans , Sheet 1 of 1 .
(1) 2 ' contours , drainage and all cultural features are
shown on the plans .
(2) Vegetative coverage is delineated and called out on
Sheet 1 of 1. There is no wildlife habitat at the
site.
(3) An existing seasonal surface runoff stream extends
through the northerly-most section of the site ;
this area is to be left in its natural state. There
is no surface water at the site. Seasonal-high
groundwater varies from approximately 5 ' to 12' .
(4) Soils types in accordance with U .S . D .A. Soils identi-
fication are delineated on the attached plan. There {
are 4 different types in the area, classified as
follows :
WnB: Windsor, loamy sand
3 to 8% slope
WnC: Windsor, loamy sand
S to 15% slope
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De : Deerfield, loamy fine sand
WaB : Walpole, fine sandy loam
3 to 8% slopes
III B 5 b) Physical Environment
(1) The site is a wooded sloping terrain of scenic
beauty.
(2) The improved site will not affect natural features .
(3)� The site is to accommodate industrial-commercial
enterprises commensurate with those in the area,
such as Western Electric, Alco , etc.
III B 5 c) Surface, Water and Soils
(1) There is a natural , seasonal drainage stream that
extends across and parallel to the northerly property
line of the site, which will be left in its natural
state.
The site drainage from the westerly k of the site
is to be collected into a cul-de-sac street and con-
veyed to existing drainage collectors along Route 125 . In
the remaining 3/4 of the site, the water will be con-
veyed to the above mentioned natural seasonal drain-
age stream. Said drainage stream currently conveys
surface runoff under Route 125 , through the Western
Electric site to the Merrimack River.
(2) Erosion control will be very minimal at the site, as
the only development contemplated is the development
of a cul-de-sac roadway which encompasses . 8 acres .
Hay bales will be used around the excavated areas
for the roadway to contain erosion or sediment seepage.
None of the surrounding areas would be affected by.
this construction.
(3) The plan delineates catch basins and surface drainage
that will be collected and conveyed through the
said drainage system as shown on the attached plans .
There is no lowland, marshland or wetland within the
proposed development area of the site.
It is the intent of the .developer to allow facilities
development that will provide for a zero increase
from surface runoff as the parcels are developed.
This is in accordance with the aforesaid noted Archie:
tectural Barriers Board,
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( ) On site sewage disposal systems will be provided for
each facility. Percolation tests and soils reveal
adequate conditions with no detrimental effects .
III B 5 d) Subsurface Conditions
(1) Limitations set by the Architectural Barriers Board
dictate that foundations for any proposed building
will not extend below the seasonal high water
elevation. .
(2) Percolation tests and soils tests reveal a sandy
loam material with an average percolation rate of
2 minutes per 1" fall . The Board of Health has records
of results .
(3) There will be on site sewage disposal systems for
each proposed facility. It should be zero impact
based on soils and percolation tests and further
based on the generally low flow characteristics pro-
duced by individual commercial buildings .
III B 5 e) Town Services
(1) It is estimated that a maximum of 3 to 4 facilities
will eventually house the site, with a maximum peak
vehicular flow of 100 cars in a 1-hour period. we
have proposed, with pending approval by the Massachu-
settsState Highway Department , acceleration and
deceleration lanes to be constructed as shown on
the attached plan, to alleviate congestion and
backup traffic on Route 125 . There is currently
approved by the State Highway Department a temporary
commercial driveway permit with acceleration-
deceleration lanes .
(2) There are no planned dev6lopments at this time.
However , all future plans will be in accordance
with the Town parking requirements , and all parking
will be off street parking.
(3) The improved road provides full access to police
and fare with added hydrants as delineated on the plan.'
(4) The improved street provides for paved streets in
accordance with the Town requirements and the follow-
ing utilities will be underground: electric, gas
water (and drainage) .
(5) N/A
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(6) The residual and static pressures in the area are
adequate for the new 8" water distribution line
extending into the' sito , with no adverse effect
on the system.
(7) N/A. There will be on--site sewage disposal systems .
III, B 5 f) General Impact
As this site has been set aside by the Town of North
Andover for a industrial complex that sets among exist-
ing improved comparable complexes , there is no detriment-
al impact on the Town.
The first building at .the Orchard Hill Commerce. Park site,
(on Parcel I-1 , "Form A" site) adjacent to the subject
subdivision, will be a brick facade, esthetically pleasing
facility, and it is the developer ' s desire to continue
with a first class type development for commerce, in-
dustry and employment of the community.
tl OF h1fiSs,®..
JOHN y�
J.
CALLAHAN
N4 �612
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