bld20110479-Echelbarger-SFR-E1-REVISED.pdf
DATE: August 3, 2011 - REVISED
TO: Michael Echelbarger mike@echelbarger.com
Rob Long robl@lsaengineering.com
FROM: Jeanie McConnell, Engineering Program Manager
RE: Plan Check #: bld20110479
Project: Echelbarger SFR Addition
Project Address: 620 Sunset Ave
The original submittal for this application included sewer and storm design that was no longer
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applicable to the project based on a meeting with Mr. Echelbarger held at the City on June 20. A
cursory review of the storm system was completed and comments from this review are provided
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below. On July 14 a revised site development, drainage and utility plan was submitted via e-mail.
Hard copies of these plans are to be provided with the next submittal. Please submit three (3) sets
of revised plans/documents with a written response to each of the items below to Marie Harrison.
GENERAL
1.The construction sequence shall be revised to include installation of the TESC measures.
2.Indicate an on-site location for a stockpile.
3.Compaction test reports will be required in areas of storm main installation to ensure 95%
compaction prior to paving. Please add notes to the plans indicating such.
4.Please add a note to the plans stating existing damaged and/or failing sidewalk, curb and gutter
sections and those sections damaged during construction, shall be removed and replaced as
required by Engineering Inspector.
5.Clearly show sections of asphalt driveway to be removed and indicate new driveway surface
material within limits of new driveway.
6.Refer to comment #4 below under Site Plan for comments regarding the sewer easement. A
sanitary sewer easement shall be provided to the City for that portion of the sewer main that
crosses private property.
A-1 SITE PLAN
1.Please add a note to this plan that references the Site Development, Drainage & Utility Plan for
Engineering Requirements.
2.The driveway approach as shown on this plan differs from that shown on the Site Development,
Drainage & Utility Plan. Please confirm the width of the driveway and curb cut and revise as
needed.
3.The rockery shown on the north side of the home has not been shown on the Site Development
Plan. The proposed rockery should be relocated so as not to prevent access to the sanitary sewer
manhole. Please revise plans accordingly.
4.The sanitary sewer easement area should be shown in the New Site Plan view as well as the
Exist. Site Plan view. It was my understanding that a new easement would need to be provided
for the section of sewer main crossing the subject property. Please confirm the referenced
easement exists in the location shown on the site plan. If an easement does exist in this location
it will likely need to be revised to clearly specify details of sewer main maintenance and
responsibility. Further discussions will be needed with the City to address future main line
responsibility, maintenance, access, etc.
STORM DRAINAGE SYSTEM:
1.The following comments (a-c) are provided by Jerry Shuster, Stormwater Program Engineer in
review of the Site Development, Drainage and Utility Plan submitted June 22, 2011 and
Drainage Report by LSA revised June 2011:
a.Small Site Minimum Requirement #1, page A-1 The text states that the proposed site
development consists of disturbing about 0.29 acres (12, 572 square feet). It also states
that the existing house was built in 1950 and therefore will be considered exempt
impervious. The paragraph then states that the project is classified as a Category 1 Small
site project. The conclusion is correct, but the reasoning is incorrect. The site is
classified as a Category 1 Small site Project because it involves over 7,000 square feet of
land disturbing activity, (see Figure B, Handout E72) not because the house was built in
1950 and this impervious is considered exempt. In addition, at the bottom of the Plan
sheet, it states the following: *REPLACE/NEW IMPERVIOUS (4,800 SF) IS
EXEMPT DUE TO DIRECT DISCHARGE BASIN. This is not a correct statement.
This only areas not regulated are those areas constructed prior to 1977.
b.Small Site Minimum Requirement #7, page A-2 Per Table 5-4 in the ESCS, flow
control is applicable in direct discharge basin but projects can be exempt from the this
requirement if a quantitative off site analysis is conducted (which you have done).
Please re-word this section to include this statement.
c.Storm Drainage Summary and Calculations The fact that the developed project will
have a less than 0.1 cfs increase in peak flows compared to the forested condition is
irrelevant. At our meeting with Mr. Echelbarger on 6/20/2011 an agreement was reached
that a direct connection to the Citys storm system, via 8 inch pipe installed on Sunset
Ave by the applicant, would convey runoff from the developed property. This concept
would be acceptable to the City under various conditions. The first condition was that a
basin capacity analysis would be done to ensure the 24 inch pipe that outfalls to the
Sound has the capacity to take the current flow in the upstream basin and the incremental
increase in flow from the subject property. This was done in the off-site analysis for
Small Site Minimum Requirement #10 that exempts the site from Flow Control (Small
Site minimum Requirement #7). This has been done to the Citys satisfaction.
The second condition was that the 8 inch pipe to be installed on the east side of Sunset
Ave will have sufficient slope to convey runoff from upstream of the subject property
and that this 8 inch pipe would be tied into the manhole that has the 24 inch line as an
outfall (call it MH#1), not the existing CB as shown on the plan (call it CB#0). Based on
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the Citys subbasin analysis, there is approximate 3.4 acres of area upstream of MH#1
coming from the north. The modeling shows a 25-year peak flow of 1.3 cfs for this
subbasin. For an 8 inch diameter pipe to handle this flow, the slope needs to be at least
1.2% (current plans show a slope of 0.88%).
The existing pipe from CB#0 to MH#1 is reverse grade and should not be used. CB#0
should replaced with a new CB with sufficient depth run a pipe with a 1.2% grade from
CB#1, and that connect to MH#1 with an 8 inch pipe with a 1.2% slope (barring any
major utility conflicts). The existing pipe between CB#0 and MH#1 should be
abandoned. The close proximity of the Citys sewage lift station necessitates a storm
system that does not overflow the area.
2.On July 21, 2011 I received an email from Rob Long indicating the storm system may be revised
to eliminate the storm connection to the downstream city storm system and potentially install a
bubble-up basin in Sunset or some other type of spreader/dissipater on site.
a.The City will not approve installation of a bubble-up basin. It may be possible to
shallow up the storm main, while maintaining no less than a 1.2% slope, so the
connections in Sunset Ave are not so deep. Ductile iron pipe will be required in areas
where less than 2-feet of cover over the storm main is proposed.
b.Stormwater could potentially be managed on site with additional design and site soils
testing. The installation of rain gardens, pervious pavements, infiltration systems, etc. is
encouraged where feasible.
3.The catch basins installed in Sunset Ave will need to be located within the gutter. In order to
minimize disruption to the curb/gutter system, the City will allow installation the main line
offset from the curb/gutter as long as additional basins are placed within the flow line where
appropriate. The basins located outside the flow line should have solid lids.
4.Please provide invert elevations for pipe connections at Yard Drain #5.
5.Please revise the impervious surface area chart to accurately reflect the total regulated
impervious area. Even though this project falls within a direct discharge basin, it shall initially
be classified as regulated. The results of the downstream analysis determine whether a detention
system is required on the site for mitigation or not. In this case it has been proven that on site
detention is not required.
SANITARY SEWER SYSTEM
1.Please remove the structural calculations for the Sewer Line Protection Box prepared by Site
Structures, dated March 18, 2008 from the Drainage Report as this sewer design is no longer
applicable to the project.
2.Provide calculations to show that the potential house loading on the main line has been
considered in the design of the proposed sewer system.
3.Please provide a profile and detail for the 8 sewer main to be encased in 18 ductile iron pipe.
a.Show house footings & callout elevations.
b.How will the sewer main be installed/supported in the DIP so pipe slope can be
maintained?
c.What will DIP connections at the manholes look like?
d.Clearly indicate manhole replacement versus installation of new. Manholes shall be
placed so as to allow for maximum achievable slope on the sewer main pipe.
e.Indicate proposed slope of sewer main in the profile.
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4.For ease of future maintenance, the proposed house sewer could connect directly to the sewer
manhole.
5.A cleanout will be required on the sewer line within 2 of the exterior of the home. Please show
on the plans.
6.Show sanitary side sewer pipe size and material.
WATER SYSTEM
1.Please relocate water meter to the back of the sidewalk.
2.Please confirm that the check valve shown on the plans is for the irrigation system and that it is
served by the existing meter.
Please contact me at 425-771-0220 or by e-mail at mcconnell@ci.edmonds.wa.us if you have
specific questions regarding these plan corrections.
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