HomeMy WebLinkAboutSPR Stormwater Pollution Prevention Plan Corners Community Center Medical Office Building.pdfJuly 18,2016
Brent Cross,P.E.
Stormwater Management Officer
Village of Cayuga Heights
836 Hanshaw Road
Ithaca NY 14850
Re:Community Corners Medical Office Building
Dear Mr.Cross,
Regarding the need for a Stormwater SPDES permit for the Community Corners project
we offer the following concept summary:
A site disturbance of more than 1 acre and less than 5 acres requires the preparation of
a Stormwater Pollution Prevention Plan (SWPPP)for review and approval by the Village
of Cayuga Heights Stormwater Management Officer (SMO)prior to the issuance of a
Building Permit.A SWPPP requires controlling erosion and sedimentation during
construction and permanent stormwater controls to reduce the rate of runoff and
provide water quality treatment.
The existing cover for the property is predominantly impervious with 69%of the site
consisting of buildings,pavements or walkways.The property contains two watersheds.
The northern watershed contains the majority of the site and will largely remain
unchanged.Runoff from several buildings and parking lots sheet drains westward
towards East Upland Road and is collected by an existing on site storm sewer.
Ultimately,all runoff from the northern watershed enters the Village’s storm system on
East Upland Road.The southern watershed consists mainly of parking and the former
bank drive through and either sheet drains southward or is collected by an existing on
site storm sewer.Runoff from the southern watershed is collected by an off site
drainage swale and conveyed southwards.
The proposed re development of the property will maintain these drainage patterns and
will increase impervious cover from 69%to 70%.As summarized in the two attached
cover type illustrations,the footprint of new impervious surfaces will increase by 0.09
acres.The project is a previously developed site in an urban area and meets the State’s
definition of a “Redevelopment Project,”requiring water quality treatment for 25%of
the existing,disturbed impervious area and 100%of the new impervious area.Per the
“Frequently Asked Questions about Permit Requirements of the SPDES General Permit
(GP 02 01)”issued by the NYSDEC on September 12,2006,and parking lot
reconstruction that does not disturb the bottom 6 inches of subbase material is not
considered a regulated disturbance and should not be included when calculating the
total disturbance.As a result,portions of the existing parking lot that will see minor
grade changes by means of pavement overlays are not included when calculating the
total disturbance.To help illustrate this,a third map has been included showing the
areas considered “full depth disturbance”(i.e.,the limits of new pavements,land
grading and full depth pavement disturbance).
To address the water quality volume requirements,a bioretention filter will be installed
in the southwest corner of the site.The filter will receive runoff from some of the
adjacent parking lot by means of sheet flow and a diversion structure will be installed to
direct water quality storm events to the filter practice from larger portions of the
parking lot while bypassing larger storm events to the Village’s storm sewer on East
Upland Road.To mitigate stormwater runoff rates,two linear detention basins will be
constructed along the southern property line to capture runoff before it enters the off
site swale.
Standard storm sewer improvements will consist of drain basins to support the site
grading.Temporary erosion and sediment control practices to be selected for the
construction phase will focus on minimizing tracking soil off site,controlling dust and
filtering any foundation dewatering discharges.The completed SWPPP,prepared in
accordance with the Village’s regulations will be submitted for your review and approval
prior to issuance of any building permit.
Please contact me with any questions or comments.Thank you.
Sincerely,
David A.Herrick,P.E.
Enclosure:(3 Sheet)
cc:T.Ciaschi
T.Covell
K.Michaels
PROPOSEDMEDICAL OFFICEBUILDING