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June 20, 2019
Zack Richardson, Stormwater Engineer
City of Edmonds
121 sth Ave N, Edmonds, WA 98020
Phone: 425-77L-O224
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Dear Zack,
Please find attached revised site plans, which reflect the changes as requested in the plan
review dated April 11, 2OL9. Our response to each comment is shown below in bold.
1. The architectural site plan refers to civil drawings for grading and drainage but no civil
drawings were submitted. A site-specific site plan showing grading and drainage along with
the improvements proposed under this permit, is required.
Update: Civil plans submitted, but drainage memo or report specific to the building permit
has not been submitted and the no summary of the proposed impervious surfaces or sizing
of the BMPs is provided. Show on the civil plans, or submit a permit specific drainage memo
that references the plat documents but which provides, the actual proposed square footages
and BMP sizing calculatíons based on this permit submittal. Additional comments regarding
necessary revisions to the civil plans are below.
A drainage memo specific for the lot has been created to address storm design.
2. It appears that the proposed impervious exceeds the plat allotted impervious surfaces
(by -5 SF); revise plan as needed to comply with plat impervious restrictions.
Update: Impervious surfaces proposed under this permit do not appear to be listed on the
civil plans; update civil cover sheet to include a table which quantifies the total proposed
roof area, hard surfaces, and pervious areas separately and list the BMP for mitigating each
of those surfaces.
The impervious areas have been revised and added to the plans and drainage memo.
3. Include an erosion and sediment control plan and ensure it protects the infiltration facility
areas from construction traffic.
Update: It appears the construction entrance is proposed over the planned pervious
driveway; relocate construction entrance and protect infiltration surfaces with construction
fencing or provide notes as needed stating that over excavation and geotechnical approval
of the subgrade is required prior to placing the ballast rock (or any material) for the
pervious pavement section.
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5920 100ih St SW, Ste #25
Lakewood, WA 98499
phone: 253-341-4157
fax: 253-336-3950
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The construction entrance has been angled to avoid the permeable pavement area
as much as possible. Orange fencing has been placed around the permeable area.
4. Civil Plansl Reviewer has concern about directing runoff from all pervious areas to a point
discharge (end of swale) above a -260/o slope and public walkway; revise plan as needed or
provide report/memo text addressing erosion and freezing concerns.
The ditch will now enter a drain and be piped to the curb in the right-of-way.
5. Civil Plans: Show the limits of the rock around the chambers and provide dimensions
between the two nearest property lines and edge of infiltration facility; setback are applied
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If utilities fall within required setbacks from the chamber system, provide additional
information (trench elevation vs chamber elevation) and/or additional improvements
(impervious liners, etc) to ensure infiltration water does not end up in utility trenches.
Chamber rock and dimensions have been added.
6. Civil Plans: Show a dimension, or minimum dimension, between the proposed structure
and infiltration system,
Tf the nronoced structrrre is within setbacks. oeotechnical anoroval of the olan lwith dates)
is required prior to approval.
Dimensions have been added.
7. Civil Plans: It appears the water service runs through the proposed chamber system and
may conflict; revise plan or provide additional information to address as needed.
The water service has been re-routed around the chambers.
B. Civil Plans: Identify where the footing drains for the home are proposed to outlet. If
proposed to connect to the chamber system, add notes accordingly and list a minimum
footing drain elevation which is a minimum of 6" above the design max water surface
Footing drain discharge location has been provided.
9. Civil Plans: Provide additional information of the actual configuration of the chamber
system:
a. Show an inspection port in plan view near the south-east end of the chamber system
and cross out all references to the inspection port being "optional" in details,
b. Clarify if the length dimensions provided represent chamber or gravel length (ie, does
30'include the 12" of rock at each end?)
c. Assuming the listed length is the chamber length (without rock), it appears the
proposed chamber length would require a fractional length of chamber (at least with
the limits of details provided); revise proposal to design the chamber system as it can
actually be built or provide additional direction for cutting and connecting a fractional
chamber along with confirmation that such approach falls within the manufacturers
recommendations and specifications.
d. Provide a pipe size and slope for the inlet pipe between the chamber and the area
drain.
Inspection port has been added, chamber dimension have been clarified, and
information has been added for the inlet pipe. The chambers are now full sections,
so no cutting is required.
10. Civil Plans: List or provide the required check damn spacing based on the design slopes,
The permeable pavement will not require check dams; the detail has been removed.
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11. Civil Plans: Provide a riser prior to the chamber system as shown in Edmonds detail SD-
637.
An area drain, as shown, may not provide sufficient space for the riser and may require a
larger basin size.
The area drain has been replaced with type 1 catch basin.
Thank you for your time and assistance in the review of this project. Should you need any
additional information, please do not hesitate to contact me at 253-984-2900 or via email at
mkel ler@beylerconsulti ng. com.
Sincerely,
Beyäev trenrnsurl*ång
Mark Keller, P.E.
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