bld20120479_add.docx
City of Edmonds
TH
121 5 AVENUE NORTH • EDMONDS, WA 98020 • (425) 771-0220 FAX(425) 771-0221
Website: www.ci.edmonds.wa.us
PUBLIC WORKS DEPARTMENT
Engineering Division
Plan Review Corrections
Plan Check : Date:
# BLD20120479 August 1, 2012
Project Name/Address:
Eslinger addition 631 Elm St.
Contact Person/Address/Fax:
Bruce O’Neill mick@designworksconstruction.net
Reviewer: JoAnne ZulaufDivision:Engineering
During review of the subject submittal, it was found that the following information, corrections, or
clarifications would need to be addressed. All Handouts and Standard Details referred to in these
comments can be accessed at our website: www.edmondswa.gov by choosing the Government tab and
Public Works| Engineering under Departments:
Please Note: Building Handouts do not include updated Engineering Division Requirements. Refer to
Engineering Handouts for all Engineering Requirements.
1. Please provide additional information regarding the proposed sewer;
a. Material, length, and size of pipe
b. 6” clean out at edge of easement with 12” cast iron locking lid and 4” clean
out at the house.
c. Provide rim and invert elevations at main and at clean outs to verify 2% slope
can be attained.
2. Please see comments from Stormwater Engineer below.
For this permit, I reviewed the following:
Storm Drainage Study for Elsinger SFR, J.C. McDonnell Engineering P.C., 6/20/2012
Detailed Drainage Plan, Sheet C2 and C3, Elsinger SFR Addition, 6/22/2012
This Category 1 Small Site Project plans on using permeable pavers and a rain garden to mitigate the
effects of 3,471 square feet of new and replaced impervious surface. The breakdown is as follows:
Rain garden: 1,984 sf of impervious (1,311 sf new roof + 600 sf new parking pad + 73 sf new side
porch)
Permeable paver driveway: 1,500 sf (self mitigating)
This information needs to be included in the text. It is difficult to tease it out of the current text.
Rain Garden
DATE FAXED/E-MAILED 7/2/2017 PAGE ___ OF __
13
Edmonds Stormwater Code Supplement (ESCS) section 5.5.3, page 35 states that if the applicant wants to
use rain gardens to handle the runoff from less than 2,000 sf if regulated impervious, it can be designed
using the “Rain Garden Handbook for Western Washington Homeowners,”
http://www.edmondswa.gov/images/COE/Services/Sustainability/Sustainability/WSU_Raingarden_han
dbook.pdf . The rain garden must hold 99% of the annual rainfall volume which means (from Table 1 in
Handbook, for well draining soils) the size of the rain garden (not bottom area ) is 10% of the tributary
area. This handbook uses a relatively simple method for determining where site soils are “well draining”
or “poor draining.” If the designed wants to use this method for designing the rain garden, the results of
the soil drainage test described in pages 8-9 of the Handbook need to be submitted to the City.
The designer has chosen to use the pre-sizing method in Handout #E72B to size the rain garden.
Handout #E72B states that to use the pre-sizing tables, the design infiltration rate needs to be
determined using the methods in Appendix C of the ESCS (such as grain size analysis). Page 2 of the
Storm Drainage Study report states: “Soils were examined by the contractor and identified as gravely
sandy loam at the rain garden site to a depth of 24.” This does not meet the requirements for
determining a design infiltration rate found in Appendix C of the ESCS.
The designer can perform the simple soil drainage test in the “Rain Garden Handbook for Western
Washington Homeowners” and size the rain garden using the Handbook or the designer can do a proper
soils test per Appendix C in ESCS and size the rain garden using the pre-sizing approach in Handout
#E72B.
Permeable Paver Driveway
The City’s permeable pavement policy,
http://www.edmondswa.gov/images/COE/Government/Departments/Public_Works/Policies/ENGR-
DEVSTM-2010-01.Permeable_Pavement_rev_1_Final.pdf , allows permeable pavers on areas less than
2,000 sf without soil testing, if the site is within the “green soils” area in Figure 2 of the policy. This site is
within he “green soils” area. Add this to the Storm Drainage Study.
The design of the permeable pavement system is incomplete. The following described in Handout #E72B,
Table 3, are required with the submittal:
Must be located greater than 5 feet from property lines
For subgrade slopes greater than 2 percent, low permeability check dams should be installed to
ensure water storage above the sloping base. This prevents the runoff from “shooting out” the
low point on the driveway. The runoff held behind the check dams give it a chance to infiltrate
into the soil. A detail of check dams should be included in the design. For example (ignore the
“outfall pipe”):
DATE FAXED/E-MAILED 7/2/2017 PAGE ___ OF __
23
Other Comments on the Detailed Drainage Plan
Sheet C2
The callout of the rain garden on sheet C2 ends with “Soil is 12” ’depth of attachment 2.” It is
o
unclear what this means (see last comment on Sheet 3 below).
Specify the aggregate on sheet C2 that is shown between the rain garden overflow and the
o
permeable driveway.
Sheet C3, Detail 3
If the rain garden is designed using the pre-sizing method:
o
The a ponding depth needs to be specified and not left to the contractor as it says in
note 1
The bioretention soil depth is 12” since only flow control is needed (change note 2)
It is unclear what is meant by note 4.
o
Plant selection should be included (note 5)
o
Attachment 2 from the Storm Drainage Study, (bioretention soil spec) should be in the
o
plans.
Jerry Shuster, P.E.
Stormwater Engineering Program Manager
City of Edmonds
121 5th Ave N.
Edmonds, WA 98020
Desk Phone: 425-771-0220 x1323
Fax: 425-672-5750
.
shuster@ci.edmondswa.us
Please resubmit 3 copies of the revised plans/documents to a Development Services Coordinator. Please
contact me at 425-771-0220 if you have specific questions regarding these plan corrections.
DATE FAXED/E-MAILED 7/2/2017 PAGE ___ OF __
33