20010944 Ver 3_Staff Comments_20080514

Project Name: River's Edge Apartments
County: Cumberland
DWQ Project #: 01-09440
Date: 5/14/08
Stormwater Review
Please note that the stormwater management plans submitted with your 401 application
received on April 22, 2008 have been reviewed but not yet approved due to the following
reasons:
1. The elevations and design of the BMPs and associated components must be based on the
final grading contours, drainage patterns, land cover and associated impervious
percentages, but not on the assumptions made that are likely to change. In addition, the
final approved stormwater plans shall be required When the final grading plans have been
finalized, please resubmit the following:
a. Two (2) copies of full size plans for the entire site on a scale 1 ":50' or larger. The
site plans must show existing site conditions and final grading contours, all
building envelopes, roads, streets, utility features, club houses (if any), wetlands
and streams and associated impacts, etc.
b. Two (2) copies of final plan details and section views of each BMP (I" : 30' or
larger) showing the pretreatment system, various zones in the main treatment
systems, high flow bypass system or overflow devices, under drain pipes and
clean-out pipes, inlet and outlet pipes, inlet and outlet velocity calculations, outlet
protection design information, soil media specifications (composition,
permeability, P-Index), planting plans, maintenance access, construction
sequence, fertilizer application requirements for vegetation establishment, etc.
c. Please pay particular attention to the following: The spacing between the
collection laterals of the underdrain system shall not be greater than l Ofeet, and
the number of clean-out pipes required is one per every 1000 square feet of BMP
surface area at a minimum.
d. Please indicate whether the outlet pipes from the Bioretention cells discharge
above or below the normal water levels of the receiving streams. If they are
unsubmerged, stream bank protection may be required based on the exit
velocities of the 10-year storm.
e. Please note that stormwater runoff from entire project site must be treated prior
to leaving the site. Please provide treatment for the northern portions of the
project area that are not being treated