Engineering and Storm Prelim Comments 2-Spence-PLN20170057.pdfI►A I HLVA us] 7_l►110LVA I
REQUEST FOR ADDITIONAL INFORMATION
Date: April 11, 2018
To: Brad Shipley, Associate Planner
From: Jeanie McConnell, Engineering Program Manager
Subject: PLN20170057, Spence 2-lot short plat
17606 72"d Ave W
The comments provided below are based upon review of the preliminary development plan &
preliminary drainage report for the subject short plat. Additional information is requested
from the applicant at this time in order to continue review of the application and provide
preliminary approval. Please ask the applicant to provide a written response to each of the
comments below and revise and resubmit plans accordingly.
Comments 1 — December 27, 2018
Comments 2 — April 11, 2018
GENERAL
1. ok
2. ok
UTILITIES
3. ok
4. ok
5. ok
6. April 11, 2018 — Refer to attached plan review comments by City Stormwater
Engineer, Zachary Richardson. Please contact Zack directly at 425-771-0220 or by
email at Zachary.richardson(a,edmondswa.gov with any specific questions you may
have regarding his comments.
December 27, 2018 comment - Please submit a stormwater report consistent with the
2012/14 Stormwater Manual and the city's Stormwater Addendum. Please include full
infiltration calculations (see Appendix B of the Addendum to determine the specific
City of Edmonds
testing requirements). Ensure the stormwater management design for the proposed single
family lot is reflective of the eve line of the house, driveway, and any patios, walkways,
etc. Show a stormwater mitigation system on the plans based on the infiltration rate and
the infeasibility checklists. If there will be an outfall, show what it connects to and where.
Plans show connection to a catch basin that is not on the city system. Please show the
catch basin as proposed. Provide approximate invert elevations for all points of connection
as well as length and size of pipe, including the City storm system inverts if applicable.
Thank you.
STO RM WATE R REVIEW COMMENTS
City of Edmonds
Engineering Division
To: Engineering Reviewer
Date: April 2, 2018
Project Name: Spence Short Plat
Permit Number: PLN20170057
Address: 17606 72nd Ave W
Review Type: Preliminary Plat (Feasibility)
Submittal Date: 3/2/2018
Reviewer: Zack Richardson, PE
City of Edmonds, Stormwater Engineer
Recommendation: I recommend that PLN20170057 be withheld until the comments
below are adequately addressed.
Review Comments:
1. The project does not appear to be satisfying the retrofit requirement per ECDC
18.30.060.D.b.i; the project must mitigate storm water using MR #5 for 25% of
the existing impervious surfaces on lot 1 in addition to mitigation for new plus
replaced surfaces on Lot 2.
2. It is unclear why the engineer selected rain gardens as the most appropriate
BMP for the site; List 1 must be reviewed in -order (top to bottom) and it appears
that the design infiltration rate above 5 in/hr allows for the use of full infiltration
and pervious pavements on -site. Revise design to implement first feasible BMP
option on list and/or revise report to significantly expand on the infeasibility of
each BMPs not selected for use.
3. Per Edmonds Addendum Checklist #4, an additional correction factor of 0.9 (for
influent control) is required to be applied to the design infiltration rate; revise
drainage report as needed to use corrected design infiltration rate.
Page 1 of 1