2021-8-24_COSV_Chad_Phillips
COMMUNITY AND PUBLIC WORKS Engineering Division – Stormwater Engineering Program 10210 E Sprague Avenue Spokane Valley WA 99206 Phone: (509) 720-5000 Fax: (509) 720-5075 www.spokanevalley.org
August 20, 2021 Lori Barlow, AICP
Senior Planner
City of Spokane Valley 10210 E. Sprague Ave. Spokane Valley, WA 99206
RE: PRD-2015-0001 “Painted Hills PRD DEIS”
DEIS Comments Dear Ms. Barlow:
This letter is being written in response to the Draft Environmental Impact Statement dated April
2, 2021, regarding the Painted Hills Planned Residential Development (PRD) and the proposed Painted Hills Flood Control Plans dated June 23, 2020. Upon review of the DEIS, the City of Spokane Valley Stormwater Engineering Program provides the following comments.
Cover Memo
• No Comment
DEIS 4-2-2021
• General Comments
o What design standard does the flood management system meet? The
design standard must be identified to adequately address the capabilities of
the system. Specifically, design standards are required for the following
elements:
Bioretention swale design
Settling pond design
Infiltration pond design
UIC pretreatment requirements
o The documents provide for a limited geotechnical evaluation. In order to
adequately address the capabilities of the flood management system, a
more detailed geotechnical evaluation is necessary.
o The documentation does not indicate the size of the storm event that
activates the stormwater and flood management system. Is the storm
event a 10-year, 25-year, or 100-year recurring storm events? The level of
system maintenance and risk of failure is dependent on how active these
systems are.
o The proponent should consider providing water source near the proposed
drywell gallery so full-scale drywell tests can be performed as part of the
Painted Hills PRD DEIS Comments August 20, 2021
Spokane Valley Stormwater Engineering Program Page 2 of 2
ongoing maintenance and operational needs of the flood management
system. Drywell tests may need to be conducted every 10 years, or
following a 10-year event, or at other intervals as established by flood
management agencies.
Appendix A - Public Comment Index
• No Comment
Appendix B - SEPA Checklist
• Question A.14.a.1
o Answer speaks to 10-year storm generating 100 cfs. Section 3.2.2.2 of the
DEIS seems to indicate the 100-year storm generates the 100 cfs design
flow.
• Question A.14.b.2 – Will stormwater be discharged into the ground?
o Answer speaks to stormwater discharge to ground per the Spokane Region
Stormwater Manual (SRSM), without providing any details. The proponent
must differentiate and provide documentation that the design standards
applicable to the development of stormwater facilities and those applicable
to flood management system are separate and distinct. The SRSM would be
applicable to the development of stormwater facilities only. The standards
within the SRSM (COSV), the Stormwater Management Manual for Easter
Washington (SMMEW) by the Department of Ecology (DOE), and even the
Highway Runoff Manual (HRM) by the Washington State Department of
Transportation (WSDOT) do not adequately cover standards for the flood
management systems.
• Question B.1.h – Proposed measures to reduce or control erosion.
o Answer speaks to measures to reduce or control erosion includes erosion
control plans outlined by the SRSM and SMMEW. This is an inaccurate
statement for this PRD. This project will require a project-specific
Construction Stormwater Permit from DOE which will prescribe the
measures to reduce or control erosion. Most likely per Appendix l of the EW
Phase ll Municipal Stormwater permit, COSV may document coverage
(erosion control) under Ecology’s CGSP and the SWPPP in leu of Erosion
Control plans.
• Question B.5.d – Proposed measures to reduce or control surface, ground, and
runoff water impacts.
o Answer speaks to proposed flood control system is designed to capture,
treat, store, and dispose of floodwaters. The response does not identify
what standards the flood control system is being designed too. Without
knowing what standards are being utilized, an adequate review cannot be
developed. Please keep in mind that the SRSM does not adequately address
flood management design standards.
Painted Hills PRD DEIS Comments August 20, 2021
Spokane Valley Stormwater Engineering Program Page 3 of 3
Appendix C - Impact Comparison Table
• No Comment
Appendix D - Standard Subdivision Alternative Environment Review
• No comment
Appendix E - Flood Management System Elements Failure Risk and Impact Summary
• No Comment
Appendix F - Traffic Impact Analysis
• No Comment
Appendix G - Truck Haul Plan Memorandum
• No Comment
Appendix H - Painted Hills PRD Biological Evaluations
• No Comment
Appendix I – Cultural Resources Survey
• No Comment
Please do not hesitate to contact me with any questions related to these comments. I appreciate your feedback.
Thank you,
Chad Phillips, PE
Stormwater Program Manager