HomeMy WebLinkAboutStormwater Report - 201 SUTTON STREET 8/20/1987 Kenneth Crouch
Sutton Street Project
Drainage Report
August 20 , 1987
Richard F. Kaminski & Associates , Inc .
200 Sutton Street
North Andover , Massachusetts 01845
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Table of Contents
Introduction
Site Description
Hydrograph Analysis
Existing Runoff
Post Development Runoff
Conclusions
Table 1 - Comparison of Existing and Post Development Runoff
Figure 1 - Existing Drainage Areas (under separate cover)
Figure 2 - Post Development Drainage Areas (under separate
cover)
Appendix A - Hydraulic Calculations
Appendix B - HEC-1 Analysis - 25 Year Storm
Appendix C - HEC-1 Analysis - 100 Year Storm
Appendix D - HEC-1 Analysis - Cochichewick Brook
INTRODUCTION
This report summarizes the result of a drainage study conducted
for Mr . Kenneth Crouch for a site on Sutton Street located across
the street from the office park at 200 Sutton Street , North
Andover , Massachusetts . The scope of the work includes a
complete investigation of the existing runoff from the site ,
proposed runoff after development, and hydrograph analysis of
Cochichewick Brook .
SITE DESCRIPTION
The site is located on Sutton Street across from the office park
at 200 Sutton Street . The portion of the site under development
is approximately 1 acre including the building, parking areas and
entrance drive . Access to the site is provided by an entrance on
Sutton Street within an existing 501 wide access easement . The
plan of the site is provided in Figure 1 .
YDROGRAPH ANALYSIS
Hydrograph analyses were completed for each of the major
components of this study including existing runoff conditions ,
post development runoff from the site and a flood hydrograph
analysis of Cochichewick Brook. The hydrograph analyses were
performed using Soil Conservation Service methods and the U .S.
Army Corps of Engineers HEC-1 Flood Hydrograph Analysis computer
program. The analysis of Cochichewick Brook included calibrating
the peak -hydrograph flows to match the flows presented in the
Flood Insurance Study for North Andover as developed by the
Federal Emergency Management Agency .
EXISTING RUNOFF
The site presently drains in two directions with the drainage
divide approximately along the center of the parcel . The
existing drainage areas are shown in Figure 1 . Approximately
one-half the site drains directly to the west into Mill Pond .
The remainder of the site drains northerly toward Sutton Street .
The total flows leaving the site are 0 . 1 cfs for the 25 year
storm and 0.3 cfs for the 100 year storm.
POST DEVELOPMENT RUNOFF
The paved impervious areas for the development of the site are
proposed to be drained using a closed piping system comprised of
manholes and catch basins . Six separate sub-areas are included
in this drainage study for the proposed site design . The sub-
areas are shown in Figure 2 . Drainage from the site is proposed
to be collected in the closed piping system and discharged
directly to Cochichewick Brook without the use of a detention
pond . The peak flow, post development from the site , occurs
approximately 12 .5 hours before the peak flow along Cochichewick
Brook passes the project site . The result of the increase in
runoff from the project site is a negligible rise in water
surface elevations along Cochichewick Brook.
CONCLUSIONS
Detention of the post development runoff on the project site is
not proposed due to the short time of concentration of runoff
from the site. The site can discharge runoff prior to the peak
of Cochichewick Brook without any significant increase in
downstream flooding.
Table 1
Comparison of Existing and Post Development Runoff
Location 25 Year Storm 100 Year Storm
(cfs) (cfs)
Existing - Total 0 .09 0 .30
Post Development - Total 2 . 90 3 .68
Proposed Change in Runoff + 2 . 81 + 3 .38
Appendix A
Hydraulic Calculations
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