20-101386-Comment Response Letter-03-21-2022-V1
March 21, 2022 Job No. 1886-001-016-0015
Ms. Stacey Welsh, AICP
Principal Planner
City of Federal Way
33325 8th Avenue S
Federal Way, WA 98003
RE: Permit #20-101386-CO
Comment Letter #3
Woodbridge Building A; 3120 South 344th Street, Federal Way
Dear Ms. Welsh:
ESM Consulting Engineers, LLC, is submitting the following responses to the comment
letter we received from you dated March 18, 2022.
In an effort to provide concise and direct responses, we have copied the review comments
below in italics and our responses are in bold.
Community Development – Planning Division
Stacey Welsh, 253-835-2634, stacey.welsh@cityoffederalway.com
1. Conditions of Approval – Please Review the enclosed Conditions Compliance
spreadsheet.
There do not appear to be any planning related comments to address prior to
issuance of the Building Permit.
Public Works – Development Services Division
Leonard Spadoni, 253-835-2732, leonard.spadoni@cityoffederalway.com
2. Conditions of Approval – Please address the comments in the enclosed Conditions
Compliance spreadsheet.
Conditions #27, and 30: With this letter, we are including a copy of the fully
executed WSDOT Developer Agreement and WSDOT Bond for Agreement
Permit.
Condition #39: On April 5, 2021, Danielle Allen with TENw specifically asked Duffy
McCollough, the WSDOT Developer Services Engineer for this project, to confirm
that Condition #39 had been addressed. In his response, he stated that the
Ms. Stacey Welsh
March 21, 2022
Page 2
WSDOT hydraulics group had reviewed the drainage report and they had no
comments. He went on to note that official approval of the project is complete
with execution of the Developer Agreement, which is included with this
resubmittal.
Condition #35: We have reached out to both Leonard and Cole, describing how
the impervious surface detention has previously been addressed with Ann Dower,
prior to her retirement.
The Building A TIR addresses the frontage improvements for both Buildings A and
B at the bottom of Section 4. Flow Control & Water Quality Facility Analysis &
Design:
The pedestrian connectivity improvements along the Weyerhaeuser Way
S (0.37 acres of sidewalk for Building A) are proposed to bypass the
detention pond, which is acceptable, because this area (estimated 0.78
acres of sidewalk for combined Buildings A & B, 0.48 acres will be
undetained and 0.28 will be mitigated by the onsite detention facility)
generates an increase in the 100 year peak flow rate of 0.36 cfs, which is
less than 0.4 cfs. The detention pond also over-detains for the frontage
improvements within the factor of safety.
The King County Surface Water Design Manual (KCSWDM) Section 1.2.3.2.E.
Mitigation of Target Surfaces that Bypass Facility (same for both 2016 and 2021
KCSWDMs) allows for some of the project runoff subject to flow control to bypass
the facility provided that all of the following conditions are met:
1. The point of convergence for runoff discharged from the bypassed target
surfaces and from the project's flow control facility must be within a quarter-
mile downstream28 of the facility's project site discharge point, AND
This requirement has been met, because the added sidewalk discharges
at the natural location, adjacent to the project site.
2. The increase in the existing site conditions 100-year peak discharge from
the area of bypassed target surfaces must not exceed 0.4 cfs, AND
This requirement has been met, because the 100-year peak flow rate
increase is 0.36 cfs.
3. Runoff from the bypassed target surfaces must not create a significant
adverse impact to downstream drainage systems, salmonid habitat, or
properties as determined by DPER, AND
The added sidewalk is not pollution generating and will not have an adverse
impact to downstream facilities.
Ms. Stacey Welsh
March 21, 2022
Page 3
4. Water quality requirements applicable to the bypassed target surfaces
must be met, AND
The sidewalk is non pollution generating.
5. Compensatory mitigation by a flow control facility must be provided so that
the net effect at the point of convergence downstream is the same with or
without the bypass. This mitigation may be waived if the existing site
conditions 100-year peak discharge from the area of bypassed target
surfaces is increased by no more than 0.1 cfs (modeled using 1 hour time
steps) or no more than 0.15 cfs (modeled using 15 minute time steps) and
flow control BMPs as detailed in Appendix C are applied to all impervious
surfaces within the area of bypassed target surfaces. One or combination
of the following methods may be used to provide compensatory mitigation
by a flow control facility subject to permission/approvals from other parties
as deemed necessary by DPER:
a) Design the project's flow control facility or retrofit an existing offsite flow
control facility as needed to achieve the desired effect at the point of
convergence, OR
b) Design the project's flow control facility or provide/retrofit an offsite flow
control facility to mitigate an existing developed area (either onsite or
offsite) that has runoff characteristics (i.e., peak flow and volume)
equivalent to those of the bypassed target surfaces but is currently not
mitigated or required to be mitigated to the same flow control performance
requirement as the bypassed target surfaces.
Compensatory mitigation using a) is provided in the proposed detention
pond as calculated in WWHM with the bypass basin. Furthermore, the
Building A detention pond has a factor of safety of 31% and with the
Building B development the combined flow control facility will have a factor
of safety of 7%.
In summary, with the 2021 KCSWDM allowed mitigation, based on the WWHM
calculations, and added factor of safety in the detention pond, the Woodbridge
Building A TIR should be adequate to address both water quality and flow control
for the proposed frontage improvements.
3. Stationing must be tied to an existing monument. Clearly identify, both on the
street improvement plans and on the horizontal control plans, which monument
was used for stationing.
This comment was received with the first round of comments on July 27, 2020 and
addressed in the response letter dated September 10, 2020 as follows:
The monument information is shown as part of the vertical datum note on
sheet 2. The plans were completed in real world coordinates matching the
datum information, including the stationing information.
Ms. Stacey Welsh
March 21, 2022
Page 4
This comment response and the added monument information on sheet 2 – Existing
Conditions was adequate, because this comment did not reappear in the second
comment letter dated April 22, 2021.
Public Works – Traffic Division
Sarady Long, 253-835-2743, sarady.long@cityoffederalway.com
4. Conditions of Approval – Please address the comments in the enclosed Conditions
Compliance spreadsheet.
Condition #28: The weight limit signs on Weyerhaeuser Way S will be installed by
March 24th.
If there are any questions or a need for further clarification, please feel free to contact me
at (253) 838-6113 and we would be happy to discuss them with you.
Sincerely,
ESM CONSULTING ENGINEERS, LLC
ERIC G. LaBRIE, AICP
President
\\esm8\engr\esm-jobs\1886\001\016-0015\document\letter-023.docx