bld20090795-Lowenthal.pdf
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:
#BLD20090720 December 11, 2009
Project Name/Address:
Lowenthal – 18720 Soundview PL
Contact Person/Address/Fax:
Marci Bryant –
vmarcibryant@msn.com
Jennifer LambertDivision:Engineering
Reviewer:
During review of the subject submittal, it was found that the following information, corrections,
or clarifications would need to be addressed. Our handouts can be found online at the City of
Edmonds web site www.ci.edmonds.wa.us under City Government/Development
Services/Engineering Division.
CA.1 – Site Plan
1.Please note if rockery is existing or proposed.
2.Please show sewer easement (see attached) on the west side of the property.
3.Please show the easement for A.F. No. 8511150244.
4.Please note whether driveway is existing to be removed or proposed driveway. If it is existing to be
removed, please also show the proposed driveway.
5.Please state whether utilities shown are existing or proposed.
a.Update plan to reflect separation requirements noted below in Sheet C3 #7.
b.Please note any proposed utilities shown on this plan sheet shall be consistent with Sheet C3.
6.Update the drawing index, Sheet C-3, to be consistent with the title stated on Sheet C3.
Sheet C1 – General Notes
1.General Notes
#7 – Please remove.
#11 – Please confirm what was intended by this note.
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nd
#17 – Please add that the traffic control will be in accordance with MUTCD. Please remove the 2
line.
2.General Sewer Notes
#5 - City of Edmonds requires that sewer pipe be bedded in granular sand or pea gravel. Please
revise note accordingly.
3.Drainage Notes
#2 – Plans do not indicate that there are any roadway ditches. It appears that note can be removed.
#3 – Please remove note. Please add a general rain garden notes section and include amended soil
notes and other pertinenet information.
4.Rain Garden Notes – Add new section
5.Construction Erosion / ESC Notes
#6 – Please add that if soils are not worked with for more than 2 days during October 1 thru May 31,
they shall be covered.
6.Erosion Control / Construction Sequence – Revise to say Construction Sequence.
#1 – Please add city engineering inspector.
#3 – Please add ‘and install catch basin erosion and sedimentary control socks as needed’.
Sheet C2 – TESC Plan and Details
1.Please note that catch basin erosion and sedimentary control socks will be installed. Add catch basin
protection detail to plans, must conform to City of Edmonds standard detail E1.3.
2.Detail 3 needs to be consistent with city standard detail E1.1. Please also note that native backfill in
trench is not permitted.
3.Detail 1 needs to be consistent with city standard detail E1.2. 4”-8” Quarry spalls not required, please
revise 2”- 4”.
4.Please identify what the solid symbols (square & circular) located along the property lines are. Do these
symbols identify property line staking?
Sheet C3 – Grading Paving & Utility Plan
1.Please identify what the solid symbols (square & circular) located along the property lines are. Do these
symbols identify property line staking?
2.Please reference all details in plan sheet.
a.It is unclear what Detail 3 is referring to. Please clarify.
3.Show bottom of footing elevations on site plan for new and existing home in order to verify grading
calculations.
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4.Please show 10’ sewer easement (see attached) on the west side of the property.
5.6” side sewer is required from the city main to the edge of right of way or easement.
a.Please show a 6” line being installed from main to edge of easement.
b.Please show a 6” side sewer clean out with 12” cast iron locking lamphole cover (with ½”
hexbolts) on edge of easement.
c.Please note on plans if you are intending to use existing side sewer lateral, from main to property
line, then it will need to be TV’d by Public Works to determine if in good working condition.
Contact Public Works at 425-771-0235. If condition is not acceptable to reuse, owner/contractor
shall be responsible to replace sewer lateral.
d.Please note on plans if you are intending to use any portion of the existing side sewer, property
line to house. It is the owner’s responsibility to TV line and submit results to Public Works to
determine if in good condition for reuse.
6.The rain garden shall not be built on top of the sanitary sewer line. Please revise accordingly.
7.Please add and clearly label all proposed and existing utilities to sheet C3 (sewer, water, power, phone,
cable, and gas).
a.Please note that all new utilities must go underground.
8.Please verify and show that 3’ minimum separation between the water service line and gas is
maintained.
9.Please show that the grasscrete driveway will extend only to property line. Those portions of the
driveway between the concrete and existing paved road shall be asphalt.
10.Please show deck and state what material the deck is constructed of.
11.Footing drains shall be piped down to the base of the slope and not allowed to discharge on the slope.
a.Permission from BNSF is required to release storm water onto BNSF right of way. Please
provide documentation showing approval from BNSF.
b.Footing drain connection to the rain gardens may be permitted if they are adequately sized.
12.Please label edge of pavement for Soundview PL.
13.Please clarify the easement area for A.F. No. 8511150244 and provide copy of recorded easement.
14.Consistent with planning comment #7 please provide an easement for the rain garden that encroaches
onto the neighboring property or revise plan showing the rain garden on entirely on the subject property.
15.Plans indicated that driveway will drain to rain gardens. Please clarify how runoff from grasscrete
driveway will be directed to rain gardens.
16.Typically when water is released to a swale a rip rap pad is provided to prevent erosion. What method
will be used at the pipe outlet into rain garden to prevent erosion?
17.Please note on site plan if the rockery running north to south (in between proposed garage and home) is
to to removed.
18.Please provide top and bottom elevations at each end of the retaining wall.
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19.It appears that the retaining wall along a portion of the south edge of the property is abutting some of the
rain gardens. Does the rain gardens add additional surcharge beyond a typical landscape backfill? If so,
please provide one of the following:
a.If there is a not a surcharge please provide a geotechnical report stating that there is no
surcharge.
b.If there is a surcharge please provide design calculations and plans for the retaining wall
designed and stamped by a WA State licensed Engineer.
Drainage/Detention Review comments from Storm Water Engineer, Jerry Shuster:
Comments on “Outline Drainage Report” (WR Consulting, Inc., November 16, 2009)
Rain gardens are not called out as a stormwater best management practice (BMP) in the existing code. The City
wants to encourage the use of these BMPs and these comments are written to “fit” rain gardens into the
constraints of the existing code.
ECDC 18.30.060.A states that any development with more than 2,000 square feet of new impervious surface
shall be required to mitigate the effects of the increased of stormwater runoff by using infiltration (in selected
areas only) or detention. The parcel in question is located in an area of the City where infiltration is permitted.
Therefore, the rain gardens will be reviewed as infiltration facilities.
ECDC 18.30.060.A.1.c. states that developments with 5,000 square feet of impervious surface that do not
discharge to a stream (which is applicable to this project) must show that post-development peak runoff rates
from the site for the 10-yr and 100-yr, 24-hour storm events are equal to the pre-development peak runoff rates
from the site for the 10-yr and 100-yr, 24-hour storm events.
The rain gardens have been designed using criteria from the 2009 King County Surface Water Design Manual
that include a sizing factor of 0.25 inches of rain garden volume per square feet of impervious surface area
served. The City will may accept use of these design criteria under the following conditions:
The 0.25 inches/sf impervious standard in the King County manual must assume an infiltration rate for
the underlying soils. This infiltration rate should be presented in the drainage report. The actual
infiltration rate for the site in the areas where the rain gardens will be located (design infiltration rate not
a field infiltration rate) needs to be verified by a geotechnical engineer. This design infiltration rate
needs to be equal to or greater than the one used for the standard in the King County manual.
The drainage analysis needs to demonstrate that the rain gardens designed to the King County standard
have release rates from the site for the 10-yr and 100-yr, 24-hour storm events under developed
conditions less that or equal to the release rate for the pre-developed conditions for the 10-yr and 100-yr,
24-hour storm events. The pre-developed condition should be modeled as secondary growth forest.
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Also, compliance with each of the 9 minimum design standards in the King County standard (Section C.2.5.1 of
the2009 King County Surface Water Design Manual) needs to be demonstrated.
Since the rain gardens are landscaping features that can be easily changed by the current and subsequent
owners, a declaration of covenant for these stormwater facilities needs to be drafted by the City and signed by
the current owners. The City is working on this provision.
The applicant must demonstrate that the westerly-most rain garden is not located in any utility easement or
critical area. In addition, a geotechnical report for this site from Otto Rosenau & Associates, Inc. (Letter to Leif
Helleren Construction Incorporated dated July 10, 2006), states on page 9:
“We recommend that on-site infiltration of runoff water be avoided at this site to reduce the amount of water
introduced into the subsurface soil and to reduce the risk of soil movement. If on-site infiltration can not be
avoided, we recommend that the infiltration system be located as far from the steep slopes as possible, and still
allow a gravity system to be built.”
Rain gardens partially rely on infiltration as a stormwater management technique. The location of the westerly-
most rain garden in the proposal needs to be specially approved by a geotechnical engineer given the
information in the 2006 Rosenau report. The City is considering requiring the owner to sign a Hold Harmless
Agreement for the rain gardens/infiltration system as proposed to allow this type of stormwater management
under the current code. This document will have the owner acknowledge that they have been fully informed of
all risks associated with using infiltration as a stormwater management technique on the property and waive and
relinquish any and all cause of action against the City arising from any issues associated with that infiltration
system now and in the future.
In addition, from the geotech report dated October 30, 2009 it states on page 2:
“Diverting stormwater from impervious surfaces near, or on, any steep slopes in the Puget Sound area can
potentially cause landslides. Thus, stormwater should not be diverted to nay point near the top or on the steep
western slope. We recommend that the stormwater be diverted to the base of the steep slope or at lease 100 feet
from the top of the steep slope.”
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.
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