pln20060144-Hiinkle-Miles_Storm Checklist-07_14_2010.xls
Stormwater Management Review Checklist
Date:7/13/2010
(For New Developments with > 5,000 sq ft of new impervious surface
Site:Hinkle-Miles Short Plat
or North Edmonds Earth Subsidence and Landslide Hazard Area )
Address:7005 &7027 - 174th St
By: Jerry Shuster, P.E.
CompleteIncompleteComments
1
Project Overview Narrative
X
(A)Description of existing site (include area of site)
The modeling assumes the disturbed area only includes the impervious area from the structures
and driveways (assumes none of the existing vegetation on lots 1 and 3 will converted to lawn or
other landscape) and that lot 4 is simply house, walkway, and driveways are in the middle of
native vegetation. The modeling for lots 1 and 3 have to assume some area of lawn or other
landscaping to proper size the detention system and be binding for the short plat. The modeling
for lot 4 also needs to include the existing lawn or landscaping area. This information is needed to
assess the pre-and post development point of compliance which is now the outflow to the
X
Meadowdale Beach Road system.
(B)Description of Proposed Development
The drainage proposal has been improved from the last submittal in that it uses gravity instead of
pumps and it preserves the natural drainage system for the site (as required by ECDC 18.30.060
B.2 - not this project is vested under the former stormwater code). Section 4.A of the Storm
Drainage Study Report states that approximately 1/2 acre upstream of sites drains onto the site.
X
Please discuss the disposition of this upstream runoff once the project is built.
(C)Discuss offsite drainage impacts to the site & from the site
Include in the report that at the bottom of Meadowdale Beach Road, the runoff enters into
X
Stilthouse Creek before being discharged to Puget Sound.
(D)Nearest mapped surface water body where site stormwater discharges.
See 1(B). Also, since the site is over 1 acre, and creating more than 5,000 sf of new impervious
Discuss disposition of storm water runoff before & after development
surface area, the report must discuss how the proposal is meeting all of minimum, requirements in
(E)
X
ECDC18.30.060.A and B.
Provide map showing general location of the site & geographical features
X
(F)
X
(G)Description of predeveloped assumptions for site
X
See 1(B)
(H)Description of post developed conditions of the site
The proposal for individual detention systems for lots 1,3, and 4 are largely responsible for the not
meeting the requirement for 1/2-the 2 year pre-development flow. By combining the flows in one
larger system (perhaps on lot 3), the project will most likely be closer to meeting that standard.
X
This is very important since the site runoff ultimately discharges to a steep gradient creek.
(I) Description of Detention Requirements for Development
X
(J)Description of Water Quality Requirements for Development
The use of a single large detention system to more closely match the specific flow control
requirements (i.e. 1/2-2yr flow off the site) is required to be investigated, since neither of the
individual systems meet this standard. If the engineer can design the flow control with more than
one system, the combined outflow hydrographs from these multiple systems must be added to
assess if the flow control standards are met for overall site at the point of compliance.
(K)Other
2
Calculations
X
See 1(B)
(A)Area Calculations
X
(B)Predeveloped Condition Runoff Curve Number
X
(C)Predeveloped Condition Time of Concentration
X
See 1(B)
(D)Post Developed Condition Runoff Curve Number
X
See 1(B)
(E)Post Developed Condition Time of Concentration
N/A
(G)Sub basin routing
7/19/2017Page 1 of 3
Stormwater Management Review Checklist
Date:7/13/2010
(For New Developments with > 5,000 sq ft of new impervious surface
Site:Hinkle-Miles Short Plat
or North Edmonds Earth Subsidence and Landslide Hazard Area )
Address:7005 &7027 - 174th St
By: Jerry Shuster, P.E.
CompleteIncompleteComments
X
(G)Predeveloped Condition Computer Model Results
X
See 1(B)
(H)Post Developed Condition Computer Model Results
X
See 1(B)
(I)Detention system assumptions
X
See 1(B)
(J)Detention system routing computer model results
X
(K)Water Quality Storm Calculations
(L)Other
3
Plan View- Drainage Conveyance
The outlet pipes from MH#5 and MH#6 are shown on sheet 2 as 8" diameter. On sheet 5, these
pipes are shown as 12" diameter. Please reconcile. The pipe connecting (No Suggestions) to
X
MH#2 is not labeled on sheet 2. Sheet 5 shows it as a 12' diameter. Please verify.
(A)Label and clearly identify existing & proposed systems
The slopes for the detention pipes are listed as 0.005 ft/ft in the drainage report. They are listed
on sheet 5 as 0.50 (no units). Add the appropriate units to sheet 5.
(B)Identify slope, length, diameter & material for all pipes
Catch Basin size/type (check size based on depth, pipe size & angles)
X
(C)
X
(D)Catch Basin, invert elevations for all pipes
Add pipe sizes
(E)Downspouts; provide connection (w/ adequate depth) to retention
X
(F)Pipe slope info versus inverts @CBs and existing pipe info
X
(G)Profile storm system and show utility crossings
X
(H)Flow arrows as necessary
The steep pipe from CB#3 to CB#2 should be called on sheet 2 to require anchoring. The type
and number of anchors for this length needs to be specified. Since HDPE pipe is being called out,
a type of anchor that incorporates sleeve should be used if HDPE is used to accommodate its
X
thermal expansion/contraction properties.
(I)Other
CB#7 is listed on sheet 5 as a stormfilter. This is not called out on sheet 2. Please reconcile.
4
Plan View & Details- Retention/ Detention (R/D) & Water Quality
Subject to review following resolution of previous comments
(A)Scaled drawing of R/D pond, vault or pipe, including tract boundaries
(B)Predeveloped & Finished Grade contours, show max water elev.
N/A
(C)Dimension all berm widths (Ponds only)
N/A
(D)Show 2 cross-sections through pond, 1 must show control structure
N/A
(E)Specify soils and compaction requirements for pond construction
N/A
(F)Location and detail of emergency overflow
N/A
(G)Rock protection details
Provide inverts of all pipes, grates, inlets, tanks, vaults & spot elev. of
(H)
pond bottom
N/A
(I)Access road to control manhole and pond bottoms, plan & details
(J)Section and plan view of control structure
7/19/2017Page 2 of 3
Stormwater Management Review Checklist
Date:7/13/2010
(For New Developments with > 5,000 sq ft of new impervious surface
Site:Hinkle-Miles Short Plat
or North Edmonds Earth Subsidence and Landslide Hazard Area )
Address:7005 &7027 - 174th St
By: Jerry Shuster, P.E.
CompleteIncompleteComments
(K)Other
(L)
Maintenance instructions for the Storm filter units must be included.
Maintenance plan
5
Plan View: Other
Subject to review following resolution of previous comments
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
7/19/2017Page 3 of 3