BLD20160096_Crosby_ENG2.pdf
City of EdmondsBLD20160096
TH
121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX (425) 771-0221
Website: www.edmondswa.gov
PUBLIC WORK DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
PermitApplication:Date:
#BLD20160096July 6, 2016
rd
Project Name/Address:
Crosby Homes Inc.–21911–93Ave W
Contact Person/Address, Fax or E-mail:
PATRICKCROSBY@FRONTIER.COM
Reviewer: JENNIFERLAMBERTDivision:
ENGINEERING
During review of the subject submittal, it was found that the following information, corrections, or
clarifications would need to be addressed. All Handouts referred to in these comments can be accessed at
our website: www.edmondswa.govunder City Government / Development Services Department /
Engineering Division then scroll down to Handouts:
st
4/8/16 –1Review
nd
7/6/16–2Review
SITE PLAN (1OF 4)
1)As changes are made to other plan sheets, please revise this sheet as needed.
GRADING & TESC PLAN (2 OF 4)
1)OK
2)OK
3)7/6/16 –Comment waspartially addressed; however, the size of the infiltration system is not
consistent in each of theplan sheets. Please revise theplans accordingly.
4/8/16 Comment: Show how the infiltration systemswill be protected from compaction(i.e.protection
fencing).
a.OK
b.Show the infiltration trench beyond the limits of the construction entrance. The location of the
infiltration trench B on this plan sheet differs than the other plan sheets. Please revise such that
the plans are consistent.
DATE E-MAILED7/6/2016PAGE (1)
City of EdmondsBLD20160096
TH
121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX (425) 771-0221
Website: www.edmondswa.gov
PUBLIC WORK DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
DRAINAGE/UTILITY PLAN (3 OF 4)
GENERAL
1)OK
New Comment–7/6/16
1)Per Installation Note 3, itappears toindicatethata special inspection is required by the engineer
of record. Is this required?
2)Installation Note 20 –Revise thenote and show thedrywell a minimum of 5’from the property
line.
3)Please reference the installationnotes on the site detail toall areas that the notes applyto.This is
tobe consistent with whatis currently shown on the plans.
4)There is a dimension along the south property line that states it is 41.5’from fence to structure;
however, it does not appear to scale as such. Was this dimension meant to show 41.5’from the
property line to thehouse?Please revise the plans accordingly.
WATER
1)OK
2)OK
3)OK
SEWER
1)OK
DATE E-MAILED7/6/2016PAGE (2)
City of EdmondsBLD20160096
TH
121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX (425) 771-0221
Website: www.edmondswa.gov
PUBLIC WORK DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
2)OK
4)OK
5)OK
STORM
1)7/6/16 –Please see comments from Herrera below.
4/8/16 Comment: The infiltration rates provided cannot not be accepted by the City due to lack of
information. Please providethe required information as outlined in Handout #E72D. Since we cannot
accept the infiltration rates, we are unable to complete the review of the proposed stormwater facility.
2)7/6/16 –Comment was not addressed. Trench B does not appear to be modeled to account for the
additional water from Trench A. There is no overflow path shown for Trench B. Lettingthe
surface water runoff discharge onto the private drive is not an option since the private drive
rd
slopes north and not to 93Ave W.
4/8/16 Comment: As stated in Handout #E72Ban overflow path must be specified. Please show
overflow paths for both trenches.
a.The proposed stormwater system shows the overflow from Trench A discharging to Trench B.
However,both trenches weredesigned based on the City’s handout which only accounts for
surface water runoff. Please provide engineering calculations to show how the proposed system
is designed to account for the impervious surface runoff and the overflow water from Trench A.
b.There is no overflow path shown for Trench B.
3)OK
4)7/6/16 –Comment was partially addressed. The plans still show 0.5’of cover over the overflow
pipe. Please revise the plans accordingly.
4/8/16 Comment: Per the inverts provided, it states that the outlet pipe of CB #1 will only have a 0.5’ of
cover; however, the requirement is a minimum of 1’ of cover in landscape areas and 2’ of cover under
drivableareas. Please revise the plans accordingly.
5)OK
6)OK
DATE E-MAILED7/6/2016PAGE (3)
City of EdmondsBLD20160096
TH
121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX (425) 771-0221
Website: www.edmondswa.gov
PUBLIC WORK DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
7)OK
8)OK
New Comment –7/6/16
9)Please clearly state and show whatsurface water runoff is proposed to discharge to each system.
It needs tobe clear theeach system is designedfor the right amount impervious area.
7/6/16 –Comments from Herrera
After reviewing the stormwater report and plans for the improvements proposed for 21911 93rd Ave W,
we have the following comments:
The applicant has the option to select the City’s SimplifiedSizing Approach or perform
1.
continuous modeling. Using the City’s Simplified Sizing Approach, a 2.7% sizing factor would be
applied, resulting in a 102.5 LF chamber for the 3,796 SF of impervious surface area. The
applicant chose to perform continuous modelingand has proposed a 56 LFchamber;however,
there are several errorsand some additional clarification needed regardingthe proposed modeling
approach as summarized below:
a.The WWHM output report included with the 6/26/16 submittal uses the Everett Rain Gage
with a Precip Scale of 0.80. The Edmonds Stormwater Supplement requires the use of the
Puget East 36 rain gage which can be selected by checking “Use WS-DOT data” on the
“Map Information” tab in WWHM.
b.The WWHM output report assumes infiltration through the wetted surface area. Due to
the steep side slopes(1H:6V), infiltration should be assumed across the chamber/trench
bottom only (Use wetted surface area = “no”)
c.It looks like the “Precipitation Applied to the Facility” box was checked. Since this is an
underground facility and the area aboveground is already accounted for in the drainage
basin areas, this box does not need to be selected (double counting of precipitation).
d.The void space in the chamber layer was calculated to be 46% in the modeling to support
the simplified sizing tool for the City. Please provide justification regarding how the 66%
void space was calculated for this chamber design.
e.Storage in the washed rock layer above the chamber is typically neglected when sizing a
chamber.Adjust riser height and effective depth accordingly.
DATE E-MAILED7/6/2016PAGE (4)
City of EdmondsBLD20160096
TH
121 5AVENUE NORTHEDMONDS, WA 98020 • (425) 771-0220 FAX (425) 771-0221
Website: www.edmondswa.gov
PUBLIC WORK DEPARTMENT
Planning • Building • Engineering
Engineering Plan Review Comments
f.The proposed site is located in the Edmonds Way (Direct Discharge basin). Please show
how the proposed chamber meets the 10-year and 100-year peak flows (0.25 cfs/acre and
0.45 cfs/acre, respectively).
g.In the Drainage Narrative, it states that “the proposal is to remove the trees”; however, this
pervious area is included as A/B forest in the WWHM output report. Disturbed pervious
areas are required to becompost-amended (using the soil quality and depthBMP T5.13)
and can be modeled as A/B pasturein WWHM.
h.Provide additional detail regarding the riser structure assumptions. Assumptions made for
the riser structure to support the simplified sizing tool for the City included:
i.Riser head = same as height ofchamber
ii.Riser diameter = 36 inches
iii.Notch height = not applicable
iv.Orifice height/diameter = not applicable
DRY UTILITIES
1)OK
2)OK
DRAINAGE/UTILITY PLAN (4OF 4)
1)As changes are made to other plan sheets, please revise this sheet as needed.
Please resubmit 3 copies of the revised plansand associated documents with a written response to each
item to a Permit Coordinator. Please contact me at 425-771-0220ext 1321or by e-mail at
jennifer.lambert@edmondswa.govif you have specific questions regarding these plan corrections.
DATE E-MAILED7/6/2016PAGE (5)