Response Letter_20180906.pdfDonna Breske
& Associates
Civil Engineering & Land Use Planning
August 15, 2018
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OE1dLf i; St:RVICES
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City of Edmonds
Attn: Jennifer Lambert, Engineering Technician
City Hall - second Floor
Edmonds, WA 98020
21 Ave A, Suite 4
Snohomish, WA 98290
Telephone (360) 294-8941
www.donnabreske.com
Subject: Response to Memorandum Request for Additional Information (2"d Review)
Donna Breske & Associates, LLC is in receipt of the City of Edmonds Request for Additional
Information (2"d Review) for PLN20170065, Ballinger View 3 Lot Short Plat 23521 75th Ave W. This
letter was prepared by Alex White, EIT of Donna Breske & Associates, LLC and reviewed and signed
by Donna L. Breske, PE. The responses to the referenced comments are as follows:
Response to Request for :additional Information (2"'1 Review):
GENERAL
1. 6125118 — Comment was addressed; however, it has been determined that curb/gutter and sidewalks
are not required. Please show the following items are being met.
a. Show the street being widened; such that there is an I1 ' lane width.
b. Show a thickened edge so that surface water runofffrom the road does not enter the site.
Response: The sidewalk, curb and gutter are no longer proposed on the project plans. An asphalt
widening and an asphalt thickened edge are proposed on the plans.
2. OK
Response: NA
3. 6125118 — Comment was addressed; however, since there is no longer a requirement for sidewalk, the
tree should remain. Please show as such on the plans.
1113118 Comment: Please show the tree located partially within the right-of-way as to be removed.
Response: The tree is shown to remain on the plans.
4. OK
Response: NA
5. 6125118 — Comment was addressed; however, the proposed driveway layouts are not consistent with
Citypolicy. During the subdivision ofproperties the City attempts to limit the number of driveways that
have access to City streets. Since your plan shows that it is feasible to have each of the three lots take
access off of a private drive, please show as such on the plans.
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[Donna Breske 21 Ave A, Suite 4
�& Associates Snohomish, WA 98290
Telephone (360) 294-8941
Civil Engineering &Land Use Planning www.donnabreske.com
1113118 Comment: Based on the proposed driveway layout the City will not approve two driveways to
be constructed off of 75th Ave W. Please show all three homes accessing off of the private access road.
Response: All proposed lots are now shown to take access from the shared access easement.
UTILITIES
1. OK
Response: NA
2. 6125118 — Comment was partially addressed. The City sewer main has not been shown accurately on
the plans. This review comment can be addressed during the Civil review phase if you choose.
1113118 Comment: Show all City utilities within 75th Ave W (Sewer has not been shown in its entirety
and water has not been shown).
Response: The location of the sewer main was gathered from a combination of a survey, and the City of
Edmonds Utility GIS map. The city will need to provide more information on what exactly is not shown
accurately, and the plans will be updated accordingly.
3. OK
Response: NA
4. 6125118 — Comment was partially addressed. The plans do not show the back of water meter at the
property line and the plans show private water service lines running within the City right-of-way. The
meter will need to be relocated to the property line and all portions of the water service (form the meter
to the house) will need to be located on private property. This review comment can be addressed during
the Civil review phase if you choose.
1113118 Comment: Show the water service lines (existing and proposed) from the main to the meter and
from the meter to individual property line.
Response: The proposed water meter locations are now shown with the back of the water meters at the
property line. All service lines beyond the water meter are shown to be located within private property.
5. 6125118 — Comment was addressed; however, it appears based on the inverts provided that portions of
the sewer is less than 2%. Please revise the plans accordingly.
1113118 Comment: Show the sewers lines (existing and proposed) to each individual lot.
a. Provide approximate invert elevations for side sewer at existing home (f relocating), property lines
and new connection to main to show feasibility.
b. The sewer must be a minimum have 10' horizontal separation from the water.
Response: All portions of the proposed sewer line are shown at 2% slope. The inverts shown of the
cleanouts within the driveways for lot 1 and lot 2 are calculated from there distance from the cleanout
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Donna Breske 21 Ave A, Suite 4
,& Associates Snohomish, WA 98290
Telephone (360) 294-8941
Civil Engineering & Land Use Planning www.donnabreske.com
shown at the property line along 751" Ave W. The sewer line is shown with 12.5' of horizontal
separation from the proposed water service lines that run parallel to it.
6. OK
Response: NA
7. 6125118 — Comment was addressed; however, it appears that there is a need for a utility easements for
the water services (See comment 4) and dry utilities (the City requires the dry utilities to enter the
property immediately and not run parallel lines within the City right-of-way). Typically there is a 10'
public easement along the property line adjacent to City right-of-ways to accommodate for utilities.
1113118 Comment: Show all utility easements.
Response: A 10' utility easement is shown along the west property boundary of the site.
WrIT"Mu
There are no further comments for storm for the preliminary short plat phase; however, see attached
document from the City's Stormwater Engineer, Zack Richardson, PE. For items to be addressed during
the Civil review phase.
STORMWA TER REVIEW COMMENTS
Recommendation: The project has demonstrated that infiltration is feasible and it appears that adequate
room is left for expansion of infiltration facilities if needed during engineering design. Accordingly, I
recommend that PLN20170065 be approved with conditions to comply with ECDC 18.30. Significant
plan revisions will be required prior to construction approval as noted below.
Review Comments:
1. It is now clear that the engineer is proposing partial dispersion and not full dispersion, however, on a
site where infiltration is feasible, infiltration must be used. Eliminate dispersion elements and revise all
BMPs to full infiltration.
a. Reverse slope sidewalks are not permitted and dispersion area does not meet downstream vegetated
flow path requirements; revise and update plan for frontage improvements as needed.
Response: Infiltration within the area of proposed sheet flow is infeasible due to the close proximity to
the steep slope in the northeast corner, and the depth of fill soils within that location. Infiltration
facilities are to be located as far west of the existing house as possible per the geotechnical
recommendation.
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Donna Breske
'& Associates
Civil Engineering & Land Use Planning
21 Ave A, Suite 4
Snohomish, WA 98290
Telephone (360) 294-8941
www.donnabreske.com
2. Revise plans to show pool and pool decking; engineer shall show which surfaces drain to sanitary
sewer or include impervious surfaces in retrofit calculation.
a. If un-able to verify a drainage connection to sanitary sewer, all pool decking (ie. concrete) shall be
effective impervious to remain; b. Wetted surface ofpool is assumed to drain to sanitary and is not
considered effective impervious.
Response: The pool and pool decking are proposed to be removed.
3. Provide developed condition exhibit with each BMP as separate sub -basin, with limits and quantities
shown, to demonstrate how impervious surfaces for each facility were calculated.
a. Clarify which facility the driveway for lot 2 will drain to (appears to be included in Lot 2 sizing, but
actually drains to shared driveway)
b. Clarify that the impervious surfaces to construct the extruded curbs (per corresponding detail) are
accounted for.
c. Clarify driveway surface vs roof surfaces draining to bioretention #4.
Response: An exhibit displaying the sub -basin areas for each bioretention, and sheet flow area has been
provided in the drainage report and Drainage Plan. Both Lot 1, and Lot 2 driveways will drain to the
easement and drain to bioretention 43. The provided exhibit displays the roof vs driving surface area
draining to bioretention #4.
4. Provide spot elevations for each grade break, angle point, or corner of improvements, or provide
profile and cross sections as needed for full construction of plan.
Response: Spot elevations and grades have been provided on both the Drainage Plan, and the Grading
plan. It may help the review to observe the grading plan and drainage plan simultaneously when
evaluating the design.
5. Revise south 3 overflow locations and/or construct additional control for the discharge from these
overflow (ie. swale) so they do not discharge directly toward the structure to the south.
Response: There is a proposed 6" berm to be installed along the south property boundary downstream
of the south 3 overflow outfalls to prevent flows from being directed toward the neighboring structure to
the south.
6. Include planting plans for each bioretention area; ensure planting plan achieves 90% coverage
within first 2-years.
Response: A note addressing the planting plans for each of the bioretention area are provided. Specific
plant species are to be selected by the contractor, or project proponent.
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Donna Breske 21 Ave A, Suite 4
& Associates _ Snohomish, WA 98290
Telephone (360) 294-8941
Civil Engineering & Land Use Planning www.donnabreske.com
7. Any utility lines within a PI projection from the bottom of the infiltration surface, may require
additional protection to prevent migration of infiltrated water through utility trench sections (ie.
impervious wrap/liner or check -dams).
Response: There appears to be a water service line that is within a 1:1 projection of bioretention 44 and
is called out have the utility trench wrapped in impervious liner.
8. Provide a down -turned elbow (or vertical tee) in the most downstream CB in any BMP which collects
runoff form polluted surfaces for floatable separation prior the infiltration facility.
Response: A vertical tee is called out to be included in the catch basins immediately upstream of the
proposed bioretention.
9. Update values in the bioretention depth table to be correct (currently all overflows are listed below
bottom and IE elevations) and include a minimum top elevation (WS +freeboard).
Response: The values in the bioretention depth table have been updated, the overflow IE ensures cover
will be provided for the overflow pipe. Minimum top elevations are provided in the depth table.
10. Provide detail as needed for construction of wall and show/identify the wall drain outlet locations.
Response: A detail for the rockeries is provided on the Grading plan (sheet 4).
11. The bio-retention cells appear to utilize the maximum amount of infiltration available for a rain
garden (uses side slope infiltration) and are designed with zero contingency for construction; while not
required, it is recommended that the engineer include some contingency for construction flaws to avoid
delays or extra costs during construction. Engineer verification of as -built performance will be required
prior to construction sign -off.
a. The low infiltration rate makes the model very sensitive to any variation; just steepening the slopes
too much would appear to fail in achieving 100% infiltration.
Response: The bioretention facilities have been designed per the requirements of the DOE manual, and
WWHM2012 calculations. The facilities are anticipated to perform as they are designed. The
bioretentions are designed to accept flow from moderately sloped (5% to 15%) driving surfaces.
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Donna Breske
& Associates
Civil Engineering & Land Use Planning
Sincerely,
Alex White, EIT
425-208-9744
Donna L. Breske, P.E.
Phone: 360-294-8941
Mobile: 206-715-9582
21 Ave A, Suite 4
Snohomish, WA 98290
Telephone (360) 294-8941
www.donnabreske.com
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