bld20100757-Clearwater-3.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 – Comments #3
Plan Check :Date:
#BLD20100757-Comments #3) April 11, 2011
th
Project Name/Address:
Clearwater SFR 22806 96 Pl W
Contact Person/Address/Fax:
Tom Berg tomberg58@yahoo.comBob Murphy rcm@murphybuilding.com
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.ci.edmonds.wa.us by clicking City Government / City
Department / Public Works / Engineering Division:
Please Note: Building Handouts do not include updated Engineering Division Requirements. Refer to
Engineering Handouts for all Engineering Requirements.
3/30/11: Resub review below.1/26/11 Done. See comments under Stormwater Mitigation.
General:
1. 3/30/11 done.
2.3/30/11 not done.1/26/11 Not Done. Add note to plans: “Replacement is required of any plat
improvements that are damaged during construction.”
3.3/30/11 not done.1/26/11 Not Done. Show dimensions of structures, deck, driveway length
and width at road and property line.
4.3/30/11 not done.1/26/11 Not Done. Note on plan: “See Grading/TESC and Drainage/Utility
Plans for more information.” Add similar information to the other plans to reference all.
5. 3/30/11 done.
6. 3/30/11 done.
7. 3/30/11 not done. 1/26/11 Not Done.Please add a general notes section to the civils.All
plans refer to General Notes but there are not any with the civil set.
8. 3/30/11 Show contours on entire property not just around house on all plans including
easement area. Contours must be shown on Lot 10 also if any portion of the new stormwater
DATE FAXED/E-MAILED 4/11/2011 PAGE ___ OF __
15
system is to be located there. The current plans note contours as “pre-development”, and
“current as-built”. I believe these refer to orginal contours prior to the plat construction and
after the plat construction. The contours that are proposed with this project also need to be
site plandrainage plan
shown on the plans. The and should show existing (today) and
proposedgrading plan
(with this project) contours. The can include all three contours,
predevelopment,existing-today (current as-built) and proposed with project. Please revise all
plans.
Site Plan:3/30/11 New Comments
1. Please provide detail of driveway with ramps to be installed consistent with City of Edmonds
standard detail (E2.26) for residential driveway.If existing, please note on plans. Show sidewalk
on plans and provide detail or call out as existing.
2. Add square footage to each section of impervious surface. If deck is uncovered wood slated
with no gravel or slab underneath, please label as “uncovered”. If covered or will have a slab or
gravel underneath, please add to impervious surface calculations.
3. Please label 11 ft area located between proposed house and west property line. Add to
impervious calcs if necessary.
Grading/TESC:
1.3/30/11 not done. 1/26/11 Not Done. Please include details of erosion control measures in
plans consistent with City of Edmonds standard details.
2.3/30/11 done.
3.3/30/11 done.
4.3/30/11 not done.1/26/11 Not Done. Please review minimum requirements of erosion
control for the classification of the project. Add all minimum requirements to the civil
general notes section.Reference Handout E 11.
5.3/30/11 not done.1/26/11 Not Done. Indicate area of disturbance. Outline on grading/tecs
plan and label with square footage of the area.
6.3/30/11 done.
Stormwater Mitigation
:(same comments as provided with Lot 8)
1.4/6/11 done.
2.4/6/11 done.
3.4/6/11 done.
4.4/6/11 addressed by proposing option C show here. See response below.
DATE FAXED/E-MAILED 4/11/2011 PAGE ___ OF __
25
c) Leave existing system untouched and propose a separate system to meet stormwater
requirements for only the proposed additional impervious surface, 6,945 sf.
i) Project would be categorized as a Small Site project Category 2 if the three
lots will use a shared system for mitigation.If the lots are mitigated individually
each would be considered a Small Site Category 1. See Chapter 5 of the
Stormwater Supplement for more information.
5.4/6/11 See response below.1/26/11 Reference. Appendix C of the Supplement provides the
acceptable methods for obtaining a design infiltration rate for infiltration trenches. In addition to
the methods in Appendix C of the Supplement, the City also accepts the "D10 methodology"
described in Volume III, Section 3.36, number 2 (including Table 3.8) in the 2005 Department of
Ecology Stormwater Management Manual for Western Washington. Once the design infiltration
rate is established, the City has tables for determining the size of the infiltration trench based on
the square feet of impervious area draining to the facility or the sizing can be obtained by the
applicant using the modeling parameters in the Supplement. Attached please find a simplified
sizing tool for low impact development or detention systems. This tool can only be used for
projects that are categorized as Small Site Category 1 or 2 sites (under 10,000 sf imp surface).
4/6/11 Stormwater Comments:
Using the Project Classification flow chart, Figure 2-1 page 5 of the 2010 Stormwater Supplement,
the proposed project falls under the classification of Small Site Category 1 (under 5000sf of
impervious surface). Stormwater requirements for this classification are outlined in Chapter 5 of the
Stormwater Supplement.
1. Chapter 5.5.2 addresses the use of LID techniques including infiltration. It states that limitations
and considerations include the following;
Infiltration is prohibited in the North Edmonds Earth Subsidence and Landslide Hazard Area (ESLHA, see Appendix
B) (ECDC Chapter 19.10), upgradient of the ESLHA, and other areas with geological instability (landslide hazard
areas).
Infiltration is prohibited in “steep slope areas” with average ground surface slopes equal to or greater than 15 percent
(see Appendix B).
Infiltration is prohibited within setbacks from the top of a designated landslide hazard or steep slope areas.
Infiltration should be applied in areas that have higher infiltration rates (including Everett gravelly sandy loam soils).
The proposed location of the infiltration system falls under two of these limiting criteria.
1) Infiltration is prohibited in “steep slope areas” with average ground surface slopes equal
to or greater than 15 percent (see Appendix B).
2) Infiltration is prohibited within setbacks from the top of a designated landslide hazard
or steep slope areas.
Referencing the attached map highlighting slope and other hazard areas, the proposed location for
the infiltration trench falls within an Erosion Hazard area, slopes of 15% to 40%.. The map shows
these areas highlighted in yellow.
2. The geotechnical report from Liu and Associates does not address the slope in the stormwater
system detail. It shows a level system. The test pits were not performed in the area that the system
DATE FAXED/E-MAILED 4/11/2011 PAGE ___ OF __
35
is proposed. Due the steepness of the slope and the differences in soils in the area, the information
given needs to more specifically address the actual proposed location.
Stormwater mitigation options may be a separate system on each property, possible detention,
infiltration at the lower part of the slope near SR 104 (if slope and infiltration rates meet
requirements), or working with the Bank for some kind of joint use system.
Please revise the Stormwater design to meet the requirements of the Edmonds Community
Development Code Chapter 18.30, the 2010 Stormwater Supplement and Appendix C.
Drainage/Utility Plan:
1.3/30/11 not done. 1/26/11 Not Done.How will the runoff from the driveway be connected to the
stormwater system? Show on plans.
2. 3/30/11 done.
3. 3/30/11 done.
4. 3/30/11 done.
5.3/30/11 done.
storm line on
6.3/30/11 partial. 1/26/11 Not Done. Show existing (plat stub) and proposed
plans.Showfull extent of system from house to stormwater system. Include rim and invert
elevations at all catch basins and cleanouts.
7. 3/30/11 done.
8.3/30/11 not done.1/26/11 Not Done. Show connection of tightline/roof drains to storm system
from house to storm line in easement.A catch basin must be installed at point of connection.
A single catch basin may be placed at the property line between Lot 7 and Lot 8. Provide rim
and all invert elevations. Remove label that says “Storm to plat storm system”.
9.3/30/11 not done.1/26/11 Add water line to plans.(and specify line material, size and length)
Show all utilities on plans (sewer, gas, power, water) from the connection at the property line
or easement to the point of connection to the residence.
10.3/30/11 not done. Show 4-6”side sewer clean out at house.
11.3/30/11 not done.1/26/11 Not Done. Label all pipe with length, material and size.
3/30/11 Additional Comments
12. Where will the footing drains be directed?If they are to be directed to the stormwater
mitigation system, a letter from the geotech will be required stating that the current proposal has
the capacity to handle the additional drainage. If they are to be directed to a separate system,
please show system on plans and provide a detail.
13. Impervious surface calculations box must be included on the Storm Drainage sheet.
DATE FAXED/E-MAILED 4/11/2011 PAGE ___ OF __
45
14. Please submit a recorded easement agreement allowing Lot 7 to cross Lot 8 to reach the
stormwater mitigation system.
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 4/11/2011 PAGE ___ OF __
55