BLD20161004_ENG1.pdf
CITY OF EDMONDS
PLAN REVIEW COMMENTS
ENGINEERING DIVISION
(425) 771-0220
City Website: www.edmondswa.gov
DATE:November 4, 2016
TO:Ben & Heather Swerk
Bswerk80@hotmail.com,heather.swerk@gmail.com
FROM:Jennifer Lambert
Jennifer.lambert@edmondswa.gov
RE:Application #: BLD20161004
Project: Swerk-Single Family Residence
Project Address: 18816 Olympic View Dr
During review of the above noted application, it was found that the following information, corrections,or
clarifications are needed. Reviews by other divisions, such as Planning, Building, or Fire may result in
additional comments. Please redline plans or submit three (3) sets of revised plans/documents with a written
response to each of the items below to a permit coordinator.
nd
Resubmittals can be made at the Development Services Department on the 2floor of City Hall. Permit
Center hours are M, T, Th & F from 8am-4:30pmand on Wednesdays from 8:30am-noon.
City of Edmonds handouts, standard details and development code can be referenced on the City website.
SHEET C1 OF C4 (Stormwater Management Site Plan)
GENERAL
1)Please revise the title “Stormwater management site plan” to “Stormwater/utility site plan”.
2)Clearly distinguish what will be installed with this project and what is currently installed (i.e.
different line types, bolding, etc.).
3)The plans do not scale as stated. Please revise the plans accordingly.
General Notes
1)Note #13 –Please revise the note to include that all pipe shall have a minimum of 2’ of cover under
driveable surfaces.
Storm Drainage General Notes
1)Note #1 –Please change ‘street use’ to ‘right-of-way permit’.
2)Add the following note –‘If rim to invert exceeds5’ (ft.) a type II manhole must be installed.’
WATER
1)It appears that a fire sprinkler system isrequired for this property. The applicant will be required to
pay for the new tap on the main and the new meter. This fee is $2970.00.
a.Please add a note that a 1” meter is to be installed
b.Please show a 1-1/2” line to be installed from the back of the meter to the house (as required
for a combination fire and domestic service line).
c.Please label the pipe material and note tracer wire to be installed on the water service line.
2)Show that there is a minimum of 3’ of horizontal separation between the water and the dry utilities
(i.e. power, phone, gas, cable, etc.).
3)Please keep in mind that there is a requirement that there is a minimum of 10’ of horizontal
separation between the water and the sewer lines.
SEWER
1)Please label the sewer easement as private.
2)Show a cleanout at the edge of easementand within 2’ of the structure.
3)Please show the invert elevations atthe stuband the house so that slope (minimum of 2%) and
coverage (minimum 2’) can be verified. If the slope of the pipe exceeds 20% the pipe will need to
be anchored.
4)Label the pipe material and size.
STORM
1)There appears to be inconsistenciesbetween the Civils and the Landscape Plan regarding
impervious areas.
a.What isthe material for the play area?
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b.If there are any areas where crushed rock can be driven on, the area will be considered
impervious.
c.The patio (stamped concrete) to the west of the garage is not shown on theCivils.
d.Please revise the plans to be consistentand revise the impervious surface calculations
accordingly.
2)Show where the footing drains will discharge to. If the footing drains are to discharge to the onsite
stormwater management system, please address the allowance for the footing drains in the design
calculations.
3)All pipes shall discharge to a catch basin prior to discharge to any stormwater management
facilities. Please revise the plans accordingly.
4)Show the overflow path for the proposed stormwater management facilityand clearly indicate/show
that it willnot negatively impact downstream properties.
5)Please provide a cross section detail of the drivewaybetween lot 1and lot 2’s driveway so thatitis
clear how the berm will be constructed to prevent runoff from lot 1 enter the stormwater
management system for lot 2. If it is not possible to prevent the runoff, the system could be
designedto accountfor theadditional imperviousarea.
6)Please show the side sewer on the segmental wall detail. The detailshouldshow that there is no
point loading on the sewer pipe.
The following comments are from theCity of Edmonds stormwater consultant.
1)The letter report (7/22/16) states that a treatment facility must be provided since the total impervious
area exceeds the 5,000 sf threshold; however, the total pollution-generating impervious surface
(PGIS) does not exceed the 5,000 sf threshold for Small Site Minimum Requirement #6, so
treatment is not required.
2)The letter report (7/22/16) and plan set (8/2/16) describe a stormwater facility that appears to be a
rain garden stacked on top of an infiltration trench, which is not an approved BMP in the 2005
Stormwater Management Manual for Western Washington (SWMMWW). Since treatment is not
required, it is recommended to simplify this design to either a rain garden or an infiltration trench or
to show the facilities in series, but not stacked on top of each other. The letter report states that
“This assemblage is commonly referred to as a rain garden, through there will be no requirement for
the intensive landscaping typical of such a facility, this being simply a BMP and used primarily for
percolation treatment of the driveway runoff.” This statement is incorrect and appears to be mixing
aspects of infiltration trenches and rain gardens. If a rain garden is selected, vegetation would be
required per the guidance in the 2005 SWMMWW.
3)The plan set (8/2/16) describes a bioswale in detail 300 and in the seeding mix specified in detail
120. A bioswale (or biofiltration swale) is designed to be a flow-through water quality treatment
BMP, not an infiltration BMP.
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4)The perforated pipe included in the rock bed in detail 300 on Sheet C2 of the plan set (8/2/16) was
not included in the WWHM modeling and can clog easily. Due to the infiltration rates, an
underdrain pipe is not necessary. If it is included in the design, it should be slotted PVC pipe and
included in the WWHM modeling inputs.
5)The letter report (7/22/16) and plan set (8/2/16) describes the compost-amended soils requirement
(BMP T5.13) instead of the bioretention soil mix required for bioretention installations. The
WWHM output report (7/13/16) also uses the “SMMWW 12 in/hr” material type which is linked to
the bioretention soil mix specifications, not BMP T5.13.
6)All disturbed pervious surface areas (areas that are not covered with an impervious area or a
stormwater BMP) shall be amended per BMP T5.13 (Post-Construction Soil Quality and Depth).
Please add a note to the plan set regarding this requirement
7)The WWHM output report (7/13/16) contains the following errors/discrepancies:
a.The Everett Rain Gage with a Precip Scale of 0.80 is used for sizing; however, 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 pervious area is 0.08090 acres (3,524 sf) which is inconsistentwith the 1,620sf
included in the letter report.
c.The infiltration rate is 100.
d.The riser height for the swale is 0.75 feet; however, the letter report specifies a 6-inch
ponding depth
e.The geotechnical site evaluation identifies the site soils as Class A soils; however, Class
C (till) soils are specified in the WWHM output report.
f.The pervious areas are modeled as pasture. If these areas will be standard
lawn/landscaping, they should be modeled as lawn.
***An alternative to the WWHM modeling approach is touse the City’s simplified sizing (Handout
#E72B) to size either an infiltration trench or a bioretention cell.***
8)WWHM2012 is the most recent and up-to-date version of the Western Washington Hydrologic
Model. Although not required, it is recommended for use over WWHM4 since it contains the latest
updates from the model developer.
9)The infiltration testing conducted at TP-1 and TP-3 are too variable to support 2 inches/hour at the
site of the proposed infiltration facility. The geotechnical report (5/16/13) states that an infiltration
trench installed along the west side of the west lot at and around TP-3 may be designed with an
infiltration rate of 2.5 inches/hour, but anywhere else on the lot should be designed for an
infiltration rate no more than 0.24 inches/hour.
10)The letter report (7/22/16) states that the project is located in the Fruitdale drainage basin and the
plan set (8/2/16) states that the project is located in the Puget Sound drainage basin. Please confirm
correct drainage basin and update forconsistency.
11)The topographical contours are not labeled in the plan set (8/2/16).
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12)The plan set (8/2/16) contains two details with the 302 callout (Infiltration Drywell on Sheet C1 and
Downspout Filter for Infiltration Facility on Sheet C2).
SHEET C2OF C4 (Storm System Details)
1)As changes are made, please revise this plan sheet as needed.
SHEET C3OF C4 (TESC & Clearing Plan)
GENERAL
1)Show the filter fence and reference the Edmonds Standard Detail E1.1.
2)Add a note that the filter socks will be added to catch basinsperEdmonds Standard Detail E1.3 as
needed,downstream from the site and areas where debris may enter the City stormwater system
from the construction/vehiclesleaving the site.
3)Show the construction entrance and reference the Edmonds Standard Detail E1.2.
4)Show protection fencing around any low impact stormwater facilitiesto prevent disturbance of the
area during other site construction activities.
5)The plans do not scale as stated. Please revise the plans accordingly.
Permanent Stabilization Notes
1)Note 1 –Please revise to state that seeding will occur as soon as disturbance of the soils have been
completed.
SHEET C4OF C4 (Grading Plans)
1)As changes are made, please revise this plan sheet as needed.
2)Please add a note to the plans that the driveway shall not exceed a 14% slope.
LANDSCAPE PLAN
1)The plans show trees and plants being installed over the existing private sewer system. Please note
that this may make maintenance an issue in the future.
2)There appears to be inconsistenciesbetween the Civils and the Landscape Plan regarding
impervious areas.
a.What isthe material for the play area?
Page 5of 6
b.If there are any areas where crushed rock can be driven on, the area will be considered
impervious.
c.The patio (stamped concrete) to the west of the garage is not shown on theCivils.
d.Please revise the plans to be consistentand revise the impervious surface calculations
accordingly.
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