STORM1_BLD20180955_19130 Olympic View.pdf0,V E[�, STO RM WATE R REVIEW COMMENTS
City of Edmonds
Engineering Division
To: Applicant
Date: August 6, 2018
Project Name: Maldazy SFR
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Address: 19130 Olympic View Dr
Review Type: Building Permit (SFR)
Submittal Date: 7/13/2018
Reviewer: Zack Richardson, PE
City of Edmonds, Stormwater Engineer
Recommendation: I recommend that BLD20180955 be withheld until the comments
below are adequately addressed. I would encourage the applicant's team to consider
additional infiltration testing in the area believe to currently infiltrate runoff; a lack of this
information means the project may not take credit for what may be occurring naturally
and results in additional infrastructure needs.
Review Comments:
1. Drainage Report: The report notes a small manmade creek which is not reflected
on the plans; update plans and report to show and identify the creek and any
associated improvements and address how creek is fed and discharged.
2. Drainage Report: Provide additional information about existing site improvements
and their classification as impervious surfaces and update retrofit mitigation value
as needed:
a. The existing "pond"; typically standing water or lined ponds are considered
impervious surfaces.
b. Gravel area north of pond; unclear if this is a walkway or the "manmade
creek" but it is not shown on the plans and needs to be identified and
addressed accordingly.
3. Drainage Report: Clean-up and clarify the interchanging use of trench
drain/French drain in upstream analysis section.
4. Drainage Report: Expand description of drainage system to clarify how surface
flows reach Fruitdale Creek and note any potential existing structure which could
be impacted.
a. Ensure description reflects, or debunks, the local depression noted in the
geotechnical report.
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5. Drainage Report: Include a table of impervious surfaces in the MR #5 section.
6. Drainage Report: "Not favorable" infiltration rates may not be sufficient to declare
bioretention infeasible; revise report to list an infeasibility criteria from Edmonds
Addendum Appendix A specifically or propose bioretention design. Provide
supporting information as needed.
7. Drainage Report: Include a sizing calculation for each BMP based on the square
footage of impervious proposed to be routed to it; trench may exceed this length,
but the minimum required length must be established in the report.
8. Drainage Report: It is unclear why the engineer routed more than 700 square
feet of impervious to the concentrated dispersion BMP; while mitigation is only
required for 25% of the surface, the BMP must be designed per standard which
restricts only 700 SF per outfall. Revise to a dispersion trench if over 700 SF
and/or revise grading as needed to isolate 700 SF of impervious surface runoff.
9. Drainage Report: Update report (and plans) to discuss or show how the
vegetated flow path meets the required conditions (max sloping, existing
vegetation, etc).
10. C2.0: Update sheet to show proposed grading (ie. proposed contours), and
identify trees requiring removal:
a. Note that the dispersion system for the driveway appears to require
additional tree removal which could be avoided.
11. C2.0: Add notes/callouts as needed to clarify that all disturbed areas are to be
restored with BMP T5.13 and add details/specifications sufficient enough for the
contractor to install soils meeting the requirements of the BMP.
12. C3.0: Update plans to show the location and full length of vegetate flow path from
each BMP with dimensions or notes as needed.
13. C3.0: Replace "downspout" with "driveway" in the pipe callout for the driveway
dispersion system (east of house).
14. C3.0: If trench drain is new, additional saw cutting may be required; update
callout as needed, show saw cut limits, and update impervious surfaces values
(replaced vs existing) as needed.
15. C3.0: Provide enough grading information (including top of drain elevation),
and/or add curbing as needed, to show how driveway runoff will be directed to
the drain as intended.
16. C3.0: List the top elevation of the dispersion trench (assumed to be equal to CB
rim) but should be listed separately.
17. C3.0: Add note: "Footing drains shall be set at XX.XX' or above." And replace
XX' with a value 6" greater than the top of dispersion trench elevation (ie. ensure
contractor maintains 6" freeboard above full dispersion trench).
18. C3.0: Add note/callout along frontage where cuts are planned: "Maintain or
restore existing road surface drainage controls (curb, berm, etc)."
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