bld20110479-Echelbarger-SFR-E2.pdfCTIT OF EDMONDS
PLAN REVIEW COMMENTS
ENGINEERI'N'G DIVISION"
(425) 771-0220
City Website: wwwxi.edniond.smams
.. .......... ........... . ... . ....... .. .. . . .. ...... . ... -
DATE: December 7, 2011
T: Jerry O'Connell
Jen-yOn-m
,,Isaenginceriiig.co
FROM: Jeanie McComiell, Engineering Program Manager
RE: Plan Check 4: bld20110479
Project: Echelbarger—SFRAddition
Project Address: 620 Sunset Ave
During review of the above noted application, it was found that the following information,
corrections, or clarifications are needed. Please redline plans or submit three (3) sets of revised
plans/documents with a written response to each of the items below to Marie Harrison,
City of Edmonds handouts and standard details can be referenced on the City website under Permit
Assistance,
Review I — August 3, 2011
Review 2 — December 7, 2011
8/3/2011 comment - The original submittal for this application included sewer and storm design that
was, no longer applicable to the project based on a meeting with Mr. Echelbarger held at the City on
June 201h. A cursory review of the storm system was completed and comments from this review are
provided below. On July 141h 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.
I , ok
2. ok
3. ok
4. ok
5. ok
6. See A-1 #4 below.
7. 12/7/11 — Please provide record of the private drainage casement across the neighboring
Property to the east.
A-1— SITE PLAN
1. 12/7111— comment not addressed.
8/3/11 comment - Please add a note to this plan that references the Site Development, Drainage
& Utility Plan for Engineering Requirements.
2. ok
3. 1217/11— comment not addressed.
8/3/11 comment - 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. 12/7/11— comment not addressed.
8/3/11 comment - 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 SYS'T'EM:
1. 12/7111 -- Please address the following comments with regards to the storm drainage report:
1. Page 1, Project Summary — remove the words "... to detention system" since a
pump system will not be installed. Also, provide more information on the off-site
drainage in terms of area and quantity under Small Site Minimum Requirement
#10.
2. Page 1, Section 5.1— The plans indicate this project will result in 4,860 square feet
of impervious surface area. The text in this section should match.
3. Page A-3 — the values in the "Site Classification Worksheet" need to match the
values on plan sheet C1. Please revise accordingly.
4. Pump System Calculations —
The sheet with Table 1, under "Friction Losses" says 4.5 inch line". All the
calculations use a 2 inch line. Please be consistent.
Please include the sheet e-mailed to Jerry Shuster, P.E. on 11/21/2011 regarding
the site modeling.
Also, the impervious and pervious values in this should match those on Sheet C1
(6,230sf impervious, the rest pervious) and remodeled. The time of
concentration of the impervious area should be less than the 10.54 minutes used.
On a small lot like this, using 6 min. would be appropriate.
5. Operations and Maintenance Guidelines — Please include O & M instructions for
the pump system.
6. Section F — Edmonds requires that only the 25 -year flows be used in a capacity
analysis, not the 100 -year. Also, using Manning "n" value of 0.012 for old concrete
pipe is not appropriate. A value of 0.015 or larger should be used.
8/3/11 comments - 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:
Page 2 of 4
7. Small Site Minimum Requirement „# 1, page A -I —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 I 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.
8. Small Site Minimum Requirement #7, _pie 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.
9. Storm Drainage Summary andCalculations— 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 City's 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 910 that
exempts the site from Flow Control (Small Site minimum Requirement 47). This has been done to the
City's 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#I), not the existing CB as shown on
the plan (call it CB#0). Based on the City's subbasin analysis, there is approximate 3.4 acres of area
upstream of MH41 coming from the north. The modeling shows a 25 -year peak flow of 13 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 0.881/o).
The existing pipe fi-om CB#0 to MH#I 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#I, 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 City's sewage lift station necessitates a
storm system that does not overflow the area.
2. N/A — storm system redesigned
3. N/A — storm system redesigned
4. 1217/11— Thank you for providing invert elevations at all structures. Please revise where
necessary to include callouts for all pipes in and out of the structures.
813/11 comment - Please provide invert elevations for pipe connections at Yard Drain #5.
5. ok
6. 1217111— A second force main is planned for the neighboring property that will discharge
to CB#4. This pipe must be capped while in a future temporary state and until approval
from the City is received. Any discharge from this line without approval by the City may
be considered and illicit discharge under City Code.
7. 12/7111. — Consistent with the City Pumping Policy, an overflow path must be designated
should failure of the system occur. Please add flow path arrows to the drainage plan and
label as "Storm System Overflow Path".
8. 1217111-- For the storm system connection on 2nd Ave, please add a catch basin in the
gutter flow line as well.
Page 3 of 4
SANITARY SEWER SYSTEM
1. ole
2. ole
3. 12/7/11 — Thank you for providing the information requested below by the 8/3/11
comments. Please revise as follows:
a. Clearly indicate DIP pipe shall be Class 52.
b. Instead of 8" PVC sewer main, please use 8" DR17 butt fused HDPE pipe.
c. Please refer to the attached schematic providing additional detail with regards to
the spacers, sewer manhole connection, etc. Incorporate notes into the plait set and
revise notes on plans as required. Also, as shown in the attached schematic, due to
the significant change in pipe size between the 18" encasement pipe and the 8"
sewer main, an additional 12" DIP pipe should be placed at the manhole
connections to allow for proper installation of the link seals. 'ne 12" DIP is only
needed at these connection points and may only be Moot in length, depending on
design.
d. Please provide an enlarged detail of the sewer main connection at the manholes.
8/3/11 comments - 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 instal led/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.
4. ole
5. ole
6. ole
7. 12/7/11 -- Replacement of the sanitary sewer main and installation of the new manholes
will require a temporary bypass. Please indicate on the plans how this will function/what
this will look like.
8. 12/7/11 — Please confirm that there is sufficient room along the north property line for
necessary shoring, etc. for installation of the manhole.
WATER SYSTEM
1. ok
2. ole
Please contact me at 425-771-0220 or by e-mail at irnecoiiiiell(ii,ei.,e(iii-i(jiids.,wa.i,is if you have
specific questions regarding these plan corrections.
Page 4 of 4