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TACOMA
2215 North 30th Street
Suite 300
Tacoma, WA 98403-3350
253.383.2422 TEL
www.ahbl.com
April 28, 2021
Alex Morganroth
City of Renton
1055 South Grady Way
Renton, WA 98057
Project: Brar Short Plat, AHBL No. 2200320.10
Subject: Response to Comment Letter dated February 8, 2021 (includes Engineering
Comments dated January 25, 2021)
LUA21-000014, ECF, SHPL-A
Dear Alex:
This letter is in response to your comments dated February 8, 2021 (which included
Engineering Comments dated January 25, 2021) regarding the above referenced project. The
comments are included below (verbatim) for your reference. Our responses are shown in bold
after each comment.
Comment Letter (February 8, 2021)
1. The level one downstream analysis field investigation has not been provided as part of
the Land Use Applications as required by the RSWDM, therefore it is recommended that
the application revise their land use application to include the level one downstream
analysis field investigation to ensure that there is no potential erosion or other concerns
that will need to be addressed by the project.
Response: A level one downstream analysis was conducted on February 16,
2021. The storm report has been updated to reflect the field inspection date.
2. All Targeted area not able to be routed to the detention vault shall be modeled as
bypass area (i.e. unmitigated flow directed to the projects downstream point of
compliance). Given the confined space on-site to locate a detention facility, it
recommend having the applicant revise their land use application to ensure that the
storm drainage system will meet the flow control requirements and will not adversely
impact the site plan configuration to locate the facility
Response: A basin swap is proposed to meet flow control. The area being
mitigated onsite is increased to match the frontage bypass.
Engineering Memo - Utility and Transportation Comments (January 25, 2021)
Code Requirements
Water
1. Proposed water system improvements are required to be shown on the engineering
plans submitted with the Civil Construction Permit Application. Civil plans for the water
main improvements will be required and must be prepared by a registered professional
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engineer in the State of Washington. Please refer to City of Renton General Design and
Construction Standards for Water Main Extensions as shown in Appendix J of the City's
2012 Water System Plan. The following water system improvements will be required as
part of the development:
a. Installation of approximately 300 feet of a minimum 8-inch diameter onsite water
main within the interior residential street (extending to the north extents of the
property) connecting to the existing 8" water main located in S 132nd St.
Response: Acknowledged for final design.
b. Installation of approximately 80 feet of a minimum 8-inch diameter on-site water
main to provide a connection to the existing 8-inch City water main located at the
neighboring property (Parcel ID: 2144800500} to the east.
Response: Acknowledged for final design.
c. A 15-foot utility easement will be required for any water main and for related
appurtenances that are not located within the public right-of-way.
Response: Acknowledged for final design.
d. Installation of additional fire hydrants as required by the Renton Regional Fire
Authority. The final location and number of the hydrants shall be determined by
the Fire Authority based on the final site plan.
Response: Acknowledged for final design.
e. Installation of a separate domestic water meter and service line (minimum 1- inch
in size) to each new home. The sizing of the domestic water meters shall be done
in accordance with Chapter 6 of Uniform Plumbing Code. A double check valve
assembly (DCVA} is required behind the domestic water meter if the buildings are
3-story or more.
Response: Acknowledged for final design.
f. A pressure-reducing-valve (PRV) is required behind each water meter because
the water pressure is over 80 psi.
Response: Acknowledged for final design.
g. Installation of a "Storz" adapter on the existing hydrants if they are not already
equipped with one.
Response: Acknowledged for final design.
2. The preliminary fire flow demand, per Renton Regional Fire Authority, is 1,000 gpm for
dwellings up to 3,600 square feet (including garage and basements.) If the dwelling
exceeds 3,600 square feet, a minimum of 1,500 gpm fire flow is required.
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a. A minimum one fire hydrant is required within 300-feet of the proposed buildings
and two hydrants if the fire flow goes up to 1,500 gpm. The existing fire hydrants
are not within 300 feet of all the proposed new lots. A minimum of 1 new hydrant
will be required. The proposal shows a hydrant at the north extent of the shared
private access.
Response: Two hydrants are proposed to meet the spacing requirements.
3. There is an existing %-inch water meter serving the existing house at 8054 S 132nd
Street, Renton WA 98178.
a. The existing meter serving the 8054 residence will require replacement and/or
relocation due to the location of the existing meter falling within the required
frontage improvements. If the water meter service line crosses the storm water
vault, a minimum of 1.5-feet of vertical clearance shall be provided between the
vault and the service line.
Response: Acknowledged for final design.
b. Depending on the extent of the relocation, the existing water service line may
need to be cut and abandoned. A water cut and cap permit will be required as part
of the Civil Construction Permit processing, and City forces will perform the work.
Response: Acknowledged for final design.
4. Please refer to City of Renton General Design and Construction Standards for Water
Main Extensions as shown in Appendix J of the City's 2012 Water System Plan.
Response: Acknowledged for final design.
5. Retaining walls, rockeries or similar structures cannot be installed over the water main
unless the water main is inside a steel casing.
Response: Acknowledged for final design.
6. Adequate separation between utilities is required. Minimum separation between water
and all other utilities is 10-feet horizontal and 1.5-feet vertical.
Response: The utility corridor along the western side of the property does not
allow for standard separations from water and the detention system. The
maximum available separation is provided between utilities. The utility separation
plan has been coordinated with Brianne from the City of Renton.
7. The development is subject to applicable water system development charges (SDC's)
and meter installation fees based on the number and size of the meters for domestic
uses and for fire sprinkler use. The development is also subject to fees for water
connections, cut and caps, and purity tests. Current fees can be found in the 2020
Development Fees Document on the City's website. Fees that are current will be
charged at the time of construction permit issuance.
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a. The SDC fee for water is based on the size of the new domestic water to serve
the project. The current water fee for a single 3/4 x 5/8-inch or 1-inch meter is
$4,450.00 per meter.
Response: Acknowledged for development of property.
b. The SDC fee for fire service is based on the size of the fire service line to serve
the project (if required).
Response: Acknowledged for development of property.
c. Water service installation charges for each proposed domestic water service is
applicable. Water Service installation for a 3/4 x 5/8-inch or 1-inch water service
line is $2,875.00* per service line. This is payable at construction permit issuance.
Response: Acknowledged for development of property.
d. Drop-in meter fee is $460.00* per meter for a 3/4 x 5/8-inch or 1-inch meter. This
is payable at issuance of the building.
Response: Acknowledged for development of property.
e. SDC fees are assessed and payable at construction permit issuance and are not
vested to the rates at land-use approval.
Response: Acknowledged for development of property.
Sewer
1. The existing septic drain field located at 8054 S 132nd St will need to be
decommissioned and removed in accordance with Washington State Department of
Health Requirements.
Response: Acknowledged for final design.
2. Proposed sewer main improvements are required to be shown on the engineering plans
submitted with the Civil Construction Permit Application. Civil plans for the sewer main
improvements will be required and must be prepared by a registered professional
engineer in the State of Washington. The following sewer main improvements will be
required as part of the development:
a. Public sanitary sewer shall be extended along the entirety of the project frontage
to the west.
i. A sanitary sewer manhole shall be constructed at the west terminus of the
sanitary sewer main extension.
Response: Acknowledged for final design.
b. Public 8-inch sanitary sewer shall be extended to the north along the length of the
shared private access to provide sewer service to the lots.
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Response: Acknowledged for final design.
c. A 15-foot utility easement will be required for any sewer main that is not located
within the public right-of-way.
Response: Acknowledged for final design.
3. The existing side sewers serving the subject parcel will be required to be capped and
abandoned during site development. New side sewers shall be installed to serve each
individual property.
a. A sewer cut and cap permit will be required for the exiting sewer stub that will not
remain in service.
Response: Acknowledged for final design.
b. A separate side sewer will be required for each building. All new sewer stubs shall
be a minimum of 611 and shall run at a slope of at least 2% to the main. Any
buildings which cannot achieve a gravity y connection will need a private lift
station(s).
Response: Acknowledged for final design.
4. The development is subject to applicable wastewater system development charges
based on the size of the new domestic water to serve each lot. These fees will be
collected at individual lot building permit application.
a. The development is pro posing connection of 3 new homes and 1 existing home
that was previously y on septic.
Response: Acknowledged for development of property.
b. SDC fee for sewer is based on the size of the new domestic water meters to serve
the project. The fees for 2021 will be increasing to $3,450 per 1" meter.
Response: Acknowledged for development of property.
c. SDC fees are payable at construction permit issuance and are not vested to the
rates at land-use approval.
Response: Acknowledged for development of property.
Surface Water
1. A geotechnical report, dated August 3, 2020, completed by South Sound Geotechnical
Consulting, for the site has been provided. Erosion control measures will need to be in
place prior to starting grading activities on the site. The report discusses the soil and
groundwater characteristics of the site including infiltration potential and provides
recommendations for project design and construction. The geotechnical report notes
"Infiltration to assist in stormwater control will be difficult at this site. The presence of
dense glacial till at fairly shallow depth will limit infiltration to lateral flow through the
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upper silty sand and weathered till horizons. Infiltration systems will be limited to shallow
dispersion facilities as allowed by the city." Geotechnical recommendations presented
need to be address within the Civil Construction Permit Application including, but not
limited to, the permanent cut and fill slope onsite shall not exceed 2:1.
Response: Shallow infiltration systems have been determined infeasible for the
site. Infiltration is not proposed. Stormwater will be managed by detention.
Erosion control measures will be addressed for final design.
2. Preliminary Drainage Plan and Technical Information Report (TIR), dated November
2020, completed by AHBL, for the site has been submitted. Based on the City's flow
control map, this site falls within the Flow Control Duration Standard area matching
Forested Site Conditions and is within the West Lake Washington - Seattle South
Drainage Basin. The development is subject to Full Drainage Review in accordance
with the 2017 Renton Surface Water Design Manual (RSWDM). All nine Core
Requirements and the six Special Requirements have not fully been discussed in the
Technical Information Report.
a. Offsite Analysis, RSWDM Core Requirement #2: A level one downstream
analysis shall be provided to identify if the proposed project shall meet any
applicable problem-specific requirements related to downstream drainage
problems.
i. The level one downstream analysis field investigation has not been
provided as part of the land Use Applications as required by the RSWDM,
therefore it is recommended that the application revise their land use
application to include the level one downstream analysis field investigation
to ensure that there is no potential erosion or other concerns that will need
to be addressed by the project.
Response: A level one downstream analysis was conducted on February 16, 2021.
There were no observed drainage problems for 0.25 mile downstream. The storm
report has been updated to include this field inspection.
b. Flow Control, RSWDM Core Requirement #3: Any proposed detention and/or
water quality vault shall be designed in accordance with the RSWDM that is
current at the time of civil construction permit application. Separate structural
plans will be required to be submitted for review and approval under a separate
building permit for the detention and/or water quality vault. Special inspection from
the building department is required. The project proposes a detention vault to
address the flow control requirements. The following are items that will need to be
addressed as part of the Civil Construction Permit Application:
Response: Acknowledged for final design.
i. Ensure report identifies that the flow control BM P shall be based on Flow
Control Duration Standard area matching Forested Site Conditions. Project
Overview, Section 1.1 Purpose and Scope, Paragraph 2, notes that Peak
Rate Flow Control Standard will be met.
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Response: Preliminary sizing has been updated with WWHM analysis to provide a
Flow Control Duration Standard evaluation.
ii. The private detention system shall be located a minimum of 10 feet from
any adjacent utility and shall be outside of any public utility easement.
location of vault, and/or utilities, will need to be adjusted as needed to meet
this requirement.
Response: The limited area for detention system and steep slope along the back
of the property limit the available space for a detention system. The maximum
available separation is provided within the limited space. The utility layout has
been coordinated with Brianne from the City of Renton.
iii. All Targeted area not able to be routed to the detention vault shall be
modeled as bypass area (i.e. unmitigated flow directed to the projects
downstream point of compliance). Given the confined space on-site to
locate a detention facility y, it recommend having the applicant revise their
land use application to ensure that the storm drainage system will meet the
flow control requirements and will not adversely impact the site plan
configuration to locate the facility.
Response: A basin swap is proposed to meet flow control. The area being
mitigated onsite is increased to match the frontage bypass.
iv. The project proposes to use Storm Tank, a proprietary detention system, to
provide storm water detention on-site. The City has approved the use of
this type of facility on a previous project (Walker Auto Dealership,
C19002207} and suggest this project be reviewed and show how the
detention system was able to provide access and meet the maintenance
requirements. The following link will allow you access to the approved Civil
Construction Plans and Technical Information Report for this project:
https://edocs.rentonwa.qov/Documents/Browse.aspx?id=1401715&d
bid=O&repo=CityofRenton
Response: Acknowledged for final design.
c. Conveyance, RSWDM Core Requirement #4: All new conveyance systems
constructed as part of the project must be sized to RSWDM standards for the total
tributary area (onsite and offsite) that the storm systems serve.
Response: Acknowledged for final design.
i. Utility separation will need to be provided. This includes separation
between storm drainage mains the proposed detention vault.
Response: The limited area for detention system and steep slope along the back
of the property limit the available space for a detention system. The maximum
available separation is provided within the limited space. The utility layout has
been coordinated with Brianne from the City of Renton.
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ii. ii. Upstream storm drainage flows will need to be captured and routed to
the downstream system. This conveyance system shall be included as part
of the Civil Construction Permit Application.
Response: The upstream area (Pass-Through Basin) is proposed to be routed
through the detention system. Preliminary facility sizing has been updated to
include the Pass-Through Area. This area does not require mitigation but is
included in the flow control analysis as existing conditions.
d. Water Quality, RSWDM Core Requirement #8: Based on the residential use of the
project, Basic Water Quality Treatment is required. The project TIR identifies the
use of a proprietary system meeting GULD approval will be used to address basic
water quality menu. This has been confirmed on the Preliminary Storm Drainage
Plan submitted with the land use application that identifies the Storm Filter which
does meet GULD approval for Basic Water Quality.
i. A full design of the proprietary system is required with the Civil Construction
Permit Application.
Response: Acknowledged for final design.
e. Onsite BMPs, RSWDM Core Requirement #9: Appropriate on-site BMPs will be
required to help mitigate the new runoff created by this development. A
preliminary drainage plan, including the application of on-site BMPs, has been
included with the land use application. The final drainage plan and drainage report
must be submitted with the civil construction permit application.
i. Final evaluation of the application of on-site BM Ps to the maximum extent
feasible will be completed during civil construction permit review. The
applicant may be required to appl y additional on-site BM Ps to meet the
minimum requirements outlined in Core Requirement #9. For instance,
Reduced Impervious Surface Credit appears to be feasible on the individual
lots and will need to be full y evaluated as part of the Single Family Building
Permits and shall be noted as part of the TIR submitted with the Civil
Construction Permit Application.
Response: Acknowledged for final design.
3. A Construction Stormwater General Permit from Department of Ecology will be required
since grading and clearing of the site exceeds one acre. A Stormwater Pollution
Prevention Plan (SWPPP) is required for this site.
Response: Acknowledged for final design.
4. The development is subject to stormwater system development charge (SDC) fee.
a. The 2021 stormwater SDC fee is $0.800 per square foot of new impervious
surface, but no less than $2,000.00. This portion of the fee will be assessed to all
new impervious surface areas (frontage, streets, private access, and sidewalks).
Additionally, each new single family residence will be subject to a rate of $2,000
per lot.
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Response: Acknowledged for development of property.
b. SDC fees are payable prior to issuance of the construction permit and are not
vested to the rates at land-use approval.
Response: Acknowledged for development of property.
Transportation
1. S 132nd Street is classified as a Collector Arterial with an existing right of way (ROW)
width of 60' as measured using the King County Assessor's Map. The existing street
section contains two (2) approximately 11-foot wide east and west-bound travel lanes
with a 9' paved shoulder along the subject property's frontage. To meet the City's
complete street standards for collector arterial streets, the minimum ROW width would
be 83 feet (2 travel lanes) requiring a ROW dedication of up to 11.5 feet. The project
proposes to construct the following required frontage improvements to match the
Earlington Town homes project to the east along the entire S 132nd Street frontage:
a. 11.5 feet of ROW dedication.
Response: Provided.
b. The Earlington Town homes project to the east was constructed under the 2-lane
scenario. The half street section will include (1) 10-foot westbound travel lane, 5-
foot westbound bike lane, 8-foot parking strip (approx. halfway along frontage
extending west), 0.5-foot curb, 8-foot planter strip with street trees, 8- foot
sidewalk, and 2-foot clear space.
Response: Frontage improvements to match Earlington Townhomes project.
c. Undergrounding of the existing and proposed electrical and communication line is
required per RMC 4-6-090, Utility Lines - Underground Installation.
Response: Acknowledged for final design.
2. Shared driveways are allowed for access to up to 4 lots provided at least one of the four
(4) lots abuts a public right-of-way, with at least sufficient frontage to comply with the
zoning width dimensions, and the subject lots are not created by a subdivision of ten
(10) or more lots. The project appears to meet the requirements of shared driveway
requirements outlined in RMC 4-6-060J.
Response: Acknowledged.
3. Current City of Renton standards require a turnaround for dead-end streets greater than
150 feet. Dead-end streets measured between 150 and 300-feet may utilize a
hammerhead turnaround meeting the requirements for emergency services access,
including a 25-foot radius and a length of 45'. Reference RMC 4-6-060H. The project
proposes the required hammerhead and the design shall be approved by the Renton
Regional Fire Authority.
Response: Acknowledged.
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4. Street grades shall not exceed 15 percent.
Response: Acknowledged for final design.
5. Project is required to meet ADA requirements for pedestrian access routes.
a. An ADA access ramp from the terminus of the sidewalk on the west side of the
frontage to the paved roadway shoulder shall be installed.
Response: Acknowledged for final design.
6. Refer to City code 4-4-080 regarding driveway regulations:
a. Driveways shall be designed in accordance with City standard plans 104.1 and
104.2.
Response: Acknowledged for final design.
b. Maximum driveway slope is 15%. Driveways which exceed 8% shall provide
slotted drains at the lower end with positive drainage discharge to restrict runoff
from entering the garage.
Response: Acknowledged for final design.
c. The maximum width of a single loaded garage driveway is 9-feet and the
maximum width of a double loaded garage driveway is 16-feet. If a garage is not
present, the maximum driveway width is 16-feet. Driveways shall not be closer
than 5-feet to any property line.
Response: Acknowledged for final design.
7. In accordance with Institute of Transportation Engineers (ITE) Trip Generation Manual,
10th Edition, the project will produce 3 additional PM Peak Hour Vehicle Trips (1 PM
Peak Hour Trip per new single-family home). Therefore, the project will not require a
traffic impact analysis.
Response: Acknowledged.
8. Paving and trench restoration shall comply with the City's Trench Restoration and
Overlay Requirements.
a. Based on the proposed utility and roadway design submitted as part of the land
use, full overlay of S 132nd Street along the property frontage may be required.
Response: Acknowledged.
9. Street lighting is not required for a 4-lot short plat per the RMC 4-6-060.F.l.a.
Response: Acknowledged.
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10. Payment of the transportation impact fee is applicable on the construction of the
development at the time of application for the building permit.
a. The 2021 rate of transportation impact fee is $10,861.69 for each new home.
Response: Acknowledged for development of property.
b. Traffic Impact Fees are payable prior to issuance of the building permit and are
not vested to the rates at land-use approval.
Response: Acknowledged for development of property.
General Comments
1. All existing and proposed utility lines (i.e. electrical, phone, and cable services, etc.)
along property frontage or within the site must be underground. The construction of
these franchise utilities must be inspected and approved by a City of Renton inspector.
Response: Acknowledged for final design.
2. Maximum exposed retaining wall height is 6-ft and shall be setback a minimum of 3-ft
from the right-of-way as outlined in RMC 4-4-040 - Fences, Hedges and Retaining Walls.
Response: Acknowledged for final design.
3. Adequate separation between utilities as well as other features shall be provided in
accordance with code requirements.
a. 7-ft minimum horizontal and 1-ft vertical separation between storm and other
utilities is required with the exception of water lines which require 10-ft horizontal
and 1.5-ft vertical.
Response: Provided.
b. The stormwater line should be minimum 5 feet away from any other structure or
wall or building.
Response: Provided.
c. Trench of any utility should not be in the zone of influence of the retaining wall or
of the building.
Response: Acknowledged for final design.
4. A civil construction permit for the site, utility and street improvements will require a
separate plan submittal. Civil construction plans shall conform to the City Renton
Drafting Standards. A licensed Civil Engineer shall prepare the civil plans. Please visit
the City's website for submittal requirements:
https://rentonwa .gov/cms/One.aspx?portalld=7922741&pageld=9687014
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Response: Acknowledged for final design.
5. A landscaping plan shall be included with the civil plan submittal. Each plan shall be on
separate sheets.
Response: Acknowledged for final design.
6. Fees quoted in this document reflect the fees applicable in the year 2021 only and will
be assessed based on the fee that is current at the time of the permit application or
issuance, as applicable to the permit type. Please visit www.rentonwa.gov for the current
development fee schedule.
Response: Acknowledged for development of property.
If you have any questions, please call me at (253) 383-2422.
Sincerely,
Ryan Inouye, PE
Project Engineer
RI/lsk
c: Scott Kaul - AHBL
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