081809 Review Comments.pdf
CITY OF EDMONDS
PLAN REVIEW COMMENTS
ENGINEERING DIVISION
(425) 771-0220
City Website: www.ci.edmonds.wa.us
DATE: August 18, 2009
TO: Fred Breske
fredbreske@gmail.com
FROM: Ed Sibrel
RE: Plan Check #: BLD20080263
Project: Breske - SFR
th
Project Address: 9330 218 Pl SW
DRAINAGE PLAN
The city would like to reiterate its support issuance of the variance/exception
necessary for the property to address its drainage concerns via infiltration (i.e., the
ECDC 18.30.065 approach); however the applicants are still required to follow the
administrative process contemplated by that code provision. This may be
accomplished by explicitly referring to that process within the Summary of the
Drainage Plan.
Don Fiene, under contract for the review of the abovementioned proposal, has
completed his review, and his comments are included in the markup of the
submittal, here attached.
Please contact me at 425-771-0220 or by e-mail at sibrel@ci.edmonds.wa.us if you have
specific questions regarding these plan corrections.
9330 218th
Stormwater Management Review Checklist
Reviewed August 18, 2009
CompleteIncompleteComments
1 Project Overview Narrative
The property has received offsite stormwater runoff since 1961 and was set aside for this purpose. Illegal
neighborhood dumping onto the site has periodically plugged this facility. The new development will further
exacerbate this problem (due to compaction, pavement, etc). The emergency overflow system is intended
for overflow drainage only & City crews have cleared the line onto the property to facilitate infiltration
onsite. The ROW and offsite drainage from the east must continue to be infiltrated on site and there must
be a clear path for the drainage to reach the infiltration gallery. To acheive this the the storm pipe from the
X
(A)Description of existing site (include area of site)
east must be extended to the properly sized, infiltration gallery proposed for this development. The
drainage report is to address the City code requirement ECDC 18.30 which requires drainage control for
all new impervious areas that are proposed to be introduced into the storm system. This is a consistent
application of the city code. The report needs to clearly demonstrate that the proposed flow rates do not
exceed the existing rates from the site for the design storm events
X
(B)Description of Proposed Development
X
(C)Discuss offsite drainage impacts to the site & from the siteSee above
Drainage from the east street catch basin must be directed to the infiltration system on Lot 1, and must
X
(D)Discuss disposition of storm water runoff before & after development
reach that site both horizontally and vertically.
Provide map showing general location of the site & geographical features
(E)
X
X
(F)Description of predeveloped assumptions for siteSee above, this is not detailed well in the narrative.
X
(G)Description of post developed conditions of the site
X
(H)Description of Detention Requirements for Development`
(I) Description of Water Quality Requirements for Development
X
(J)Other
X
See report markups
2 Calculations
X
(A)Area Calculations
X
(B)Predeveloped Condition Runoff Curve Number
X
(C)Predeveloped Condition Time of Concentration
X
(D)Post Developed Condition Runoff Control Number
X
(E)Post Developed Condition Time of Concentration
X
(F)Sub basin routing
X
(G)Predeveloped Condition Computer Model Results
Properly label the output info from the facility. It appears that there is 0.55 cfs outflow from the infiltration
X
(H)Post Developed Condition Computer Model Results
facility, which would not be acceptable.
X
(I)Detention system assumptionsSee above
(J)Detention system routing computer model results
(K)Water Quality Storm Calculations
(L)Other
3 Plan View- Drainage Conveyance
X
(A)Label and clearly identify existing & proposed systemsDrainage from the east street catch basin must be directed to the infiltration system on Lot 1
X
(B)Identify slope, length, diameter & material for all pipes
Catch basins must have 18" minimum deep catch upstream of infiltration system.
(C)Catch Basin size/type (check size based on depth, pipe size & angles)
X
(D)Catch Basin, invert elevations for all pipes
(E)Downspouts; provide connection (w/ adequate depth) to retention
(F)Pipe slope info versus inverts @CBs and existing pipe info
(G)Profile storm system and show utility crossings
(H)Flow arrows as necessary
Drainage from the east street catch basin must be directed to the infiltration system on Lot 1
X
(I)Other
X
See plan markups.
4 Plan View & Details- Retention/ Detention (R/D) & Water Quality
1) Note the volume requirement per the calculations "Total volume required = " 2) Show connection from
X
(A)Scaled drawing of R/D pond, vault or pipe, including tract boundariesstorm drain to the east. 3) Add note: Contractor shall verify drain rock quantities with Engineering
Inspector.
(B)Predeveloped & Finished Grade contours, show max water elev.
(C)Dimension all berm widths (Ponds only)
X
(D)Show 2 cross-sections through pond, 1 must show control structure
(E)Specify soils and compaction requirements for pond construction
(F)Location and detail of emergency overflow
(G)Rock protection details
Provide inverts of all pipes, grates, inlets, tanks, vaults & spot elev. of
(H)
pond bottom
(I)Access road to control manhole and pond bottoms, plan & details
(J)Section and plan view of control structure
(K)Other
5 Plan View: Other
Show location, identification and dimensions of buildings, property lines,
(A)
`
streets, alleys & easements
Show locations of structures on abutting properties within 25 feet of
(B)
proposed project site.
Show section details of all retaining walls & rockeries, sections through
(C)
critical portions
(D)Other