HomeMy WebLinkAbout2380-CO-COMM-Renton-2018-06-22-Response.pdfPBG, LLC
L AND D EVELOPMENT & C IVIL E NGINEERING C ONSULTANTS
5130 S. 166th Lane ● SeaTac, WA 98188 ● T 206.229.6422
June 22, 2018
Clark H. Close
Senior Planner
Community and Economic Development
City of Renton
1055 S. Grady Way, 6th floor
Renton, WA 98057
Subject: Cho Short Plat / LUA18-000177, SHPL-A
Dear Mr. Close:
This letter is written in response to your May 30th, 2018 review of the submittal for the above
referenced project. Please find enclosed with this letter the revised plan sheets and report
addressing your comments.
Comments from your letter have been addressed below:
1. The sizing calculations for the detention facility only includes about twenty five percent
(25%) of the total area that should be included, as the existing pervious surface area is
incorrectly included from the calculations. Detention modeling has been revised to
include the entire 0.783 acres within the clearing limit. Refer to Table 4 of the TIR.
2. Raingardens are proposed as an onsite BMPs for the roof run-off. The sizing calculations
for the detention facility takes ten percent (10%) credit that is specified for bioretention
areas. Raingardens and bioretention areas are fundamentally different. Raingardens do
not receive sizing credits for the sizing of detention facilities. Either remove the credits
from the sizing calculations or bioretention will need to be utilized in place of the
proposed raingardens and sized as outlined in Appendix C of the 2017 Renton Surface
Water Design Manual. WWHM modeling no longer takes credit for LID BMP’s. Refer
to Table 5 of the TIR.
3. The Engineer who prepared the TIR is claiming exemption from water quality treatment
since the pollution generating impervious surface (PGIS) is less than 5,000 square feet
(SF). However, this total does not include the roadway widening PGIS. The total PGIS for
the project is approximately 7,749 square feet (SF), which exceeds the maximum criteria
to qualify for the water quality treatment exemption. Either reduce the PGIS to less than
5,000 SF or provide alter quality treatment as outlined in the 2017 Renton Surface Water
Design Manual. Water quality will be provided for the private road and driveways
through the construction of permeable pavement surfaces. Water quality for the
frontage improvements will be provided by a StormFilter media system.
PBG, LLC
L AND D EVELOPMENT & C IVIL E NGINEERING C ONSULTANTS
5130 S. 166th Lane ● SeaTac, WA 98188 ● T 206.229.6422
4. The TIR does not reference Special Requirement #6, which is applicable to the project.
The TIR has been amended to show compliance with SR #6. There are no open
facilities such as flow control or water quality treatment ponds.
We appreciate your assistance with this project. Please feel free to contact me if you have
questions regarding this resubmittal.
Han Phan, P.E. | Civil Engineer
Sincerely,
PBG, LLC