HomeMy WebLinkAboutCDP 2017-0008; Thermo-Newton Parking; Expansion Parking Lot Drainage; 2017-12-04,: I® lffl ;mrm, di I RECORD COPY
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City of Carlsbad
Engineering Department
1635 Faraday Ave.
Carlsbad, CA 92008
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RE: Thermofisher Expansion (Parking Lot) Drainage
An analysis was performed of the possible effects on the drainage scheme at the
Thermofisher Site on Newton Drive, in the City of Carlsbad, California. The following is
the results of the analysis.
Background
The existing project site consists of a developed , industrial park, surround on the north
and east sides by undeveloped land. The entire lot consists of approximately 695,000 sf
(15.96 acres), with the developed portion of the lot covering approximately 434,000 sf
(9.96 acres) of the lot.
Drainage from the 5 acres of undeveloped property flows away from the project site,
towards the canyon located on the east and north sides of the developed lot. Drainage
from the developed portion of the lot is collected by catch basins along the west and
south sides of the building, before travelling to the west and to the north where it
discharges from the site through a 30" RCP storm drain.
The project proposes the removal of landscaping and parking areas and replacing them
with 2 sets of concrete steps, an asphalt cart path, and parking areas constructed of
pervious asphalt. In addition there is minor grading being performed to facilitate the
construction of a cart path. The total amount of impervious area being added and/or
replaced is approximately 4,060 square feet, with approximately 2,000 of that total being
new impervious area.
Hydrology
The estimated pervious area for the proposed portion of the site is approximately 65,000
sf {1.49 acres) with the estimate impervious area being estimated at approximately
369,000 sf {8.47 acres). The increase in impervious area is approximately 2,000 sf
(0.046 acres). The 2,000 square feet increase in the impervious area represents an
increase of less than 0.5% impervious area.
The 0.5% increase represent a statistically insignificant increase in area that is within the
margin of error for our measurements of the areas of impervious and pervious for the
project.
Therefore, it is not anticipated that there will be a significate increase in run off from the
project.
, Michael Baker Inti ional
Hydraulics
The project discharges to the Municipal storm drain on the west side of the site. As
stated above, the pipe consists of a 30" RCP (reinforced concrete pipe). The change in
a 30" pipe from the addition of 2,000 sf represents less than 0.4% percent increase in
flow which is insignificant.
Hydromodification
The project is not subject to hydromodification because this project does not increase
the impervious area by more than 5000 square feet, and is therefore not a priority
project. Non-priority projects are not subject to hydromodification.
Storm Water Treatment Control
The project is not subject to Storm Water Treatment Control because this project does
not increase or replace the impervious area by more than 5000 square feet, and is
therefore not a priority project. Non-priority projects are not subject to Storm Water
Treatment Control.
Conclusion
Because the change in flow from the existing to proposed condition is insignificant, no
effects in the project area or downstream area anticipated.
ichard S. Tomlinson, Jr. PE, Q
Project Manager II
Land Development
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