Peer Review ltr Preliminary Storm
8730 Tallon Lane NE, Suite 200 Lacey, WA 98516 Office 360.352.1465 Fax 360.352.1509 scjalliance.com
July 20, 2018
Tami Merriman, Associate Planner
City of Yelm Community and Economic Development Department
105 Yelm Avenue West
Yelm, WA 98597
Re: Peer Review – NPR Recycling
SCJ Project No. 0605.05 Task 41
Dear Tami:
The City has requested SCJ Alliance to conduct a preliminary peer review of the proposed stormwater
management system for the NPR Recycling projecting including a review of the Preliminary plans and
Preliminary Drainage Report in accordance with the 2014 Stormwater Management Manual for Western
Washington. This review consisted of the following documents:
· City of Yelm Administrative Site Plan Review Application
· Preliminary Plans dated 6/1/2018
· Preliminary Drainage Report dated June 2018
Review Understanding:
Previously, City of Yelm policy was that all storage yard areas that had any possibility of waste, auto’s, or
whatever, were to be paved to meet stormwater treatment. In the recent past, there has been a switch
that gravel storage be allowed, if it meets the 2014 Stormwater Management Manual for Western
Washington (referred to as the stormwater manual for the remainder of this letter). The purpose of this
review is to establish whether the proposed design meets the stormwater manual requirements and
comment on any changes that are required.
The stormwater manual generally defines gravel surfaces as impervious surfaces, therefore the drainage
design as provided meets the intent of the stormwater manual. We also made the following
observations regarding the drainage design:
General Comments
1. Per the plans provided, a bioretention swale is identified but the swale does not meet the
minimum requirements for a swale. (e.g. bioretention swales imply longitudinal slopes or a
method of conveyance) Please clarify if the design intent is as a bioretention swale or a
bioretention cell. The design of the selected facility type then needs to meet the design
requirements of the stormwater manual.
2. The project must incorporate BMP T5.13 Post Construction Soil Quality and depth within
landscaped areas.
July 20, 2018
Page 2
Preliminary Plans
3. Sheet P1.1 – Grading construction note #4 references a v-bottom ditch but appears to callout a
pipe in the plan.
Preliminary Drainage Report
4. Applicable references, charts and figures within the preliminary drainage report need to
reference the 2014 version of the stormwater manual.
5. Document the 6-month, 24-hour rain event can infiltrate through the facility within 48 hours in
accordance with SSC-4 of the 2014 stormwater manual.
6. Part 4 - MR #6 is not addressed within the drainage report.
7. Part 5.1 - The detention volumes represented for the proposed facilities is not shown in the
WWHM output. Confirm the detention volumes are correct or demonstrate basis of volume
calculations.
Should you have any questions or comments, please contact me at (360)352-1465 at your earliest
convenience.
Sincerely,
SCJ Alliance
Jared VerHey, PE
Project Manager
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