HomeMy WebLinkAboutCT 2016-0002; TOWN HOUSE; PRELIMINARY HYDROLOGY AND STORM WATER MANAGEMENT REPORT; 2016-11-09CITY OF CARLSBAD
ENGINEERING DIVISION
VINCENT L SAMPO-ROE 44173
ENGINEER OF WORK
PRELIMINARY HYDROLOGY AND STORM WATER MANAGEMENT
REPORT
FOR
TOWN HOUSE
Na 44173
PREPARED BY:
SAMPO ENGINEERING, INC.
171 SAXONY ROAD, SUITE 213
ENCINITAS, CA 92024
(760) 436-0660
Railyards Flats
Standard Development Project
Sampo Engmeermg, Inc.
11/9/2016
Introduction;
The subject property is approximately 0 225 gross acres and is located at 2677 State
Street m the City of Carlsbad The ptopafy has been previously developed as an
automotive repair shop, asphalt concrete covers the majonty of the site and there is an
existing garage on-site The subject property's storm water runoff sheet flows Westerly &
Southwestarly from the State St Right of Way to the existmg storm dram inlet located on
the westerly property line & Right of Way of the rear alley. The pipe exiting the mlet ties
to the existing 66" RCP that runs South-North along the west side of the alley This
project proposes to mamtam the histoncal drainage pattern
The project proposes to construct a 4 story, mixed-use condomimum building on State
Street, just North of the recently completed Railyard Lofls and campfire projects. This
project proposes 8 luxury condominium umts and 1,600 sf of ground-level professional
office space. With 18 residential parking spaces ova: an on-grade parking garage.
Hydrology Sximmarv;
A hydrology study utilizing the Rational Mrthod was performed for the existmg and
proposed conditions and the results are as follows. The existmg condition is composed of
1 hydrologic basin that meludes the entire propaty The existmg drainage basm has a
tnbutary area of 0.225 AC with a runoff coefficient of C=0.91 and an anticipated flow for
the 100-year storm of 1 43 CPS. The proposed drainage basm, ova: the same area,
produces a runoff coefficient of C=0.93 and an anticipated flow for the 100-year storm of
1 47 CPS, The total site impavious surface area is mcreased by 314 SP fixim the existmg
condition Thus, the anticipated inarease in storm water runoff volume has beai
calculated as 43 CP. A detention basm is proposed m the pariong garage m an effort to
mitigate peak storm flows for the total site m the develops condition, refer to attadied
calculations.
Storm Water Quality SninmarY;
The project has been determmed to be a "Standard Project" usmg the City of Carlsbad
Storm Wato: Standards Questionnaire (E-34) and is therefore exempt fix)m priority
project requirements. The development proposes to reduce the discharge of pollutants
off^te by utilizing Source Control and Low Impact Development (LID) BMP's to the
maximum extent practical. Storm water treatment will be done by installing krystar
downspout filters on the roof downspouts and utilizmg a sand oil separator on ail runoff
collected in the proposed parking garage trench drain All storm water runoff generated
by the new structure will be collected, treated as outlmed above, detamed m a concrete
vault m the parkmg garage before bemg released and conveyed to the 66" RCP public
storm dram m the rear alley
Rail3urds Plats Sampo Engmeermg, Inc.
Standard Development Project 11/9/2016