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Congestion Relief & Bus Rapid Transit Projects
CAG -05-115
600 —108th Avenue NE, Suite 405
Bellevue, WA 98004
Main 425-456-8500
Fax 425-456-8600
May 10, 2005
Gregg Zimmerman, Public Works Director
City of Renton
1055 South Grady Way
Renton, WA 98055
Re: Concurrence Letter - Johns Creek Outfall
Dear Mr. Zimmerman:
This letter documents that the City of Renton and the Washington State Department of
Transportation (WSDOT) concur with the 15% design for the Johns Creek Outfall.
Johns Creek Background
The City of Renton and WSDOT have jointly investigated a non-traditional proposal to
provide water quality treatment and stormwater controls for runoff from the I-405
Corridor Project from MP 4.59 to MP 6.09. Water quality treatment will be provided for
all runoff from the I-405 right-of-way, which will include 7.3 acres of new impervious
area from the 1-405 improvements in the Johns Creek watershed. The Johns Creek
watershed is 1082 acres. Upstream of 1-405, the watershed includes 868 acres of
primarily residential land use. I-405, including the new impervious area, occupies 72.6
acres. The watershed downstream of I-405 is primarily commercial land use and includes
215 acres of land (including the I-405 area). The increased impervious area from
expansion of I-405 would increase impervious area within the basin by less than I%. All
water within the basin currently drains to Johns Creek, and this water is currently
discharged near the entrance to Gene Coulon Memorial Beach Park.
Under existing conditions, runoff from this part of I-405 is combined with runoff from
the upper Johns Creek watershed (City of Renton, residential area), and then discharged
to the City of Renton drainage system located in the lower basin. The City storm system
routes the runoff westerly along N 8th to where it joins the North 8th Street/Garden
Avenue North storm system. The Garden Avenue North storm system then conveys the
water north to where it discharges to a series of intermittent stream and culvert
conveyances on Johns Creek beginning approximately 200 yards upstream of the
entrance road to Gene Coulon Memorial Beach Park.
—Greg Zimmerman rr.r
April 25, 2005 Page 2
A traditional stormwater response for this watershed would construct a series of
stormwater vaults within the existing WSDOT Right of Way (ROW) to provide both
water quality treatment and flow control, as required by the WSDOT Highway Runoff
Manual. The City of Renton and WSDOT held a series of discussions in 2004 and early
2005 to develop a more efficient and cost-effective solution to managing stormwater
within the Johns Creek basin.
15% Design Development
The City of Renton and the I-405 team held a series of discussions to develop the
proposed Johns Creek Outfall as the stormwater component of the North 8th Street HOV
Direct Access Project. This design concept was investigated sufficient to allow
preparation of a 15% design package.
The design addresses a series of potential concerns and opportunities that were identified
through the discussions. Protection of Gene Coulon Memorial Beach Park facilities and
plant materials was identified as a major concern, which triggered additional study,
consideration of several discharge locations, and careful routing of the discharge pipe to
minimize disturbance to Park facilities. Minimizing disruption to Park operations and the
Parks users was also a major concern and resulted in limitations on construction timing
and activities. Sizing the new stormwater facilities to handle anticipated future flows
from both I-405 and from residential areas in the upper watershed was also addressed
during preliminary design. Finally, minimizing impacts to the backwater channel of
Johns Creek was also a major concern which triggered studies of the projected changes to
water surface elevation and stream flow velocities.
Preliminary design discussions identified the opportunity to forgo stormwater detention
(flow control) for this project. The purpose of stormwater detention is to provide
protection to downstream areas from erosion and flooding problems associated with
increased flows as a result of a project. Studies as part of preliminary design established
that detention would not provide any meaningful additional protection to downstream
areas, and detention would not serve a useful purpose for this project. The bulk of the
downstream conveyance for this project will be drainage pipes specifically sized and
constructed to convey both current and anticipate future flows. This piped system has
been sized specifically for the projected future flows and will not be affected by either
erosion or flooding issues. A short section of Johns Creek within Gene Coulon Memorial
Beach Park that would receive the additional discharge was investigated during
preliminary design. Studies established that this is a backwater channel of Lake
Washington, and the channel is sufficiently large that neither water elevation nor flow
rate will be noticeably changed by the project's peak discharges.
To address concerns identified during the preliminary design process, a series of
conditions were developed which state the specific concerns and how they will be
addressed during final design and construction. A full listing of the conditions, which
will guide final design and construction, is attached (Johns Creek Outfall Attachment 1)
Washington State
'W, Department of Transportation
Page 2
...
—Greg Zimmerman *8W
April 25, 2005 Page 3
Final Design Development
The City of Renton and WSDOT anticipate continuation of the cooperative design
process during the development of Final Design for this project. Development of the
final design will be guided by the conditions established during the preliminary design
process and described in the attached Johns Creek Outfall Attachment 1. Funding for the
final design and construction of the North Renton Congestion Relief and Bus Rapid
Transit Project is dependent on future funding actions, such as legislative action by the
State of Washington or a Regional Transportation Investment District (RTID) public
vote.
Concurrence
I am anticipating a project that will set a high standard of cooperation between the City of
Renton and WSDOT. I ask, by signing below, that the City and WSDOT concur with the
15% design for the Johns Creek Outfall. This 15% design will be examined by the
project's NEPA and ESA documents, which are currently in preparation. The City and
WSDOT commit to work together, guided by the conditions in the attached Johns Creek
Outfall Attachment 1, to develop the final design, obtain necessary approvals, and
prepare associated permits once funding becomes available.
Craig J. Stone, PE
Urban Projects Director
City of Renton Concurrence:
hA
ate
Kathy Keolker-Wheeler
Mayor, City of Renton
cc: Administrators Executive Committee members
City Design Team members
I-405 Project Team file
Washington State
Department of Transportation
Attest:
&x oc a. &)i
Bonnie I. Walton, City Clerk
Page 3
Johns Creek Outfall
Attachment 1
This document outlines an understanding between the City of Renton and the Washington
State Department of Transportation (WSDOT) to establish a stormwater discharge to
Johns Creek at Gene Coulon Memorial Beach Park in the City of Renton. Included in
this outline is a listing of the responsibilities of each party as part of the anticipated
agreement, and the 15% design for the Johns Creek Outfall and related conveyance
systems (Appendix E: Johns Creek Backwater Analysis and Appendix F: Outfall Pipeline
Hydraulic Analysis, Supplements to Preliminary Hydraulic Report, North 8th HOV
Direct Access).
Both parties are aware that the Johns Creek Outfall is a part of the larger Renton to
Bellevue Project and that funding for the Renton to Bellevue Project has not been
allocated at the time this document was prepared. Both parties presume that funding will
occur in the foreseeable future and they wish to complete this letter of concurrence now
to provide the certainty that the Johns Creek Outfall and the associated flow exemption
will be included as designed in the Renton to Bellevue Project once funding is secured
and construction commences.
Both parties agree:
- the Park needs to be protected during construction
♦ That Gene Coulon Memorial Beach Park is an important recreational resource to the
City of Renton, and that substantial efforts should be made during construction of the
Johns Creek Outfall to minimize disruption of Park uses; and
- the. Johns Creek Backwater Study is accurate
♦ That the Johns Creek Backwater Study based upon the 15% design work accurately
describes the existing condition of the local drainage system in the vicinity of Gene
Coulon Memorial Beach Park at the time of this agreement, and accurately anticipates
the effects of Johns Creek Outfall on the local drainage systems in the Johns Creek
watershed. An updated hydrologic and hydraulic analysis of the proposed Johns
Creek Outfall storm system improvements and the Johns Creek channel down to Lake
Washington will be conducted as part of the project final design; and
- flows under discussion currently go to Johns Creek
♦ That stormwater runoff flows from the affected section of I-405 and tributary areas of
the City are currently routed to Johns Creek via local drainage systems, and these
flows are contributing to infrastructure limitations in the local conveyance systems;
and
- the change in impervious area in the Johns Creek Watershed from 1-405 improvements
is small
♦ That construction of the Renton to Bellevue Project would increase impervious area
within the Johns Creek watershed by approximately 7.3 acres. This amounts to less
than 1% increase in impervious area across the Johns Creek watershed, which would
result in a very small increase to existing flows; and
Attachment 1 page 1
Johns Creek Outfall
- providing water quality treatment to I-405 runoff will improve Johns Creek
♦ That providing enhanced water quality treatment to 100% of the stormwater flows
from the I-405 corridors existing and proposed pollution generating pavement
surfaces within the Johns Creek watershed would result in an improvement to water
quality of existing storm water discharges to Johns Creek; and
- that detention is not necessary in this instance as it provides no additional protection to
downstream resources
♦ That providing detention to I-405 runoff routed to the Johns Creek Outfall prior to
discharge would provide limited environmental or resource protection benefit. The
outfall location, as shown to the north of the Park entrance, is within the backwater
area of Lake Washington, there is sufficient channel capacity in the affected reach of
Johns Creek to safely accommodate unrestricted stormwater runoff flows from the I-
405 corridor, and that post -project flow velocities would be low enough that there are
no erosion or bank stability concerns; and
- the new system will also convey the 100 yr localflows from upstream basins
♦ That the 1-405 conveyance shall convey the 100 -year design storm of 3 upstream sub -
basins of Johns Creek that currently cross I-405 to the new discharge so that these
flows are removed from the local conveyance systems they currently occupy; and
- the new conveyance system and outfall will reduce flooding near Southport bridge
♦ That establishing the Johns Creek Outfall will reduce flooding in the vicinity of the
Southport stream crossing immediately upstream of Gene Coulon Memorial Beach
Park; and
- the new conveyance system will free capacity in existing conveyance systems
♦ That establishing the Johns Creek Outfall will free capacity in existing local drainage
and conveyance systems.
City of Renton agrees:
- to provide easements upon approval of final design
♦ To approve drainage and temporary construction easements submitted by WSDOT on
properties owned by the City to allow construction and operation of the stormwater
outfall and related conveyance system as described in the 15% design document
(Appendix E: Johns Creek Backwater Analysis and Appendix F: Outfall Pipeline
Hydraulic Analysis, Supplements to Preliminary Hydraulic Report, North 8rh HOV
Direct Access).; and
- to participate in finalizing design
♦ To participate in discussions with WSDOT and the Design/Build team as part of
progressing the 15% design to the final design such that a final design review by the
City will take place in timely manner to approve required City permits for
construction; and
- to support' direct, discharge waiver if one is needed
♦ To support a WSDOT request for a direct discharge waiver to Department of Ecology,
should such a waiver be deemed necessary as part of the permitting process for the
Renton to Bellevue Project. City support will be based on hydraulic and hydrologic
analyses reviewed by the City and is subject to any environmental reviews that may
be performed in the future; and
Attachment 1 page 2
Johns Creek Outfall
f
- to work towardsconsensus to address new issues
♦ To work with WSDOT and the Design/Build team to reach consensus on how to
address new issues as they develop as part of the implementation process for the
Johns Creek Outfall; and
- to own, operate, and maintain the conveyance' system outside of WSDOT ROW
♦ To accept ownership upon completion of construction, and to operate and maintain
those portions of the conveyance system which lie outside of the WSDOT ROW as
shown in the 15% design review plans. The City's agreement to maintain these
systems is contingent upon the City's approvals in regards to ease of maintenance
access. A final agreement addressing maintenance issues will be developed as part of
final design and will address which portions of the final will system will be
maintained by the City and which portions will be maintained by WSDOT, and how
maintenance costs will be distributed between the two parties.
WSDOT agrees:
- to construct as planned
♦ To construct the Johns Creek stormwater outfall as described in the 15% design
document (Appendix E: Johns Creek Backwater Analysis and Appendix F: Outfall
Pipeline Hydraulic AnalA Supplements to Preliminary Hydraulic Report, North
8th OV Direct Access). and
- to participate in finalizing design
♦ To participate in discussions with City of Renton and the Design/Build team as part
of progressing the 15% design to the final design; and
- to make no project changes without concurrence from Renton
♦ To make no changes to the 15% design document (Appendix E: Johns Creek
Backwater Analysis and Appendix F: Outfall Pipeline Hydraulic Analysis,
Supplements to Preliminary Hydraulic Report, North 8th HOV Direct Access) or the
area draining to this outfall without prior concurrence from the City of Renton; and
- to provide enhanced water quality treatment for 1-405 flows
♦ To provide enhanced water quality treatment methods (per the approved water quality
treatment methods defined in the WSDOT Highway Runoff Manual that are
applicable at the time of final design) for 100% of the existing and proposed
pollution generating pavement surfaces within the I-405 corridor which is routed to
the Johns Creek discharge; and
- to provide conveyance capacity to handle 100yr flows from I-405
♦ To provide conveyance capacity sufficient to handle stormwater flows generated by
the implementation phase of the Renton to Bellevue Project; and
- to provide conveyance capacity to handle 100yr flows from offsite basins for future
land -use conditions
♦ To provide conveyance capacity sufficient to handle current and future off-site flows
from upstream tributary areas identified on Sheet 1, Exhibit A, and upstream land
use for ultimate development as determined from the City of Renton Zoning Map,
adopted 12/22/03 (Appendix E: Johns Creek Backwater Analysis), and as described
in Appendix E: Johns Creek Backwater Analysis. It is agreed that WSDOT will
capture off-site flows upstream of I-405 and route them directly to the Johns Creek
Attachment 1 page 3
Johns Creek Outfall
Outfall without detention or treatment, thereby diverting flows away from existing
City of Renton local conveyance systems west of I-405. It is agreed based upon the
15% design that 200 cfs constitutes sufficient capacity to meet this requirement,
which may be revised as part of the final design; and
- to own, operate, and maintain the conveyance system within the WSDOT ROW
♦ To own, operate, and maintain the portions of the Johns Creek conveyance system
that lie within the WSDOT ROW. A final agreement addressing maintenance issues
will be developed as part of final design and will address which portions of the final
will system will be maintained by the City and which portions will be maintained by
WSDOT, and how maintenance costs will be distributed between the two parties.
♦ To secure all necessary Section 4(f), Section 6 and/or other approvals related to use of
the City park as part of the WSDOT project.
Protection of Park Uses, Timing Issues
- to; minimize impacts to Park operations
♦ To work diligently with City of Renton Parks Department and the Design/Build team
during construction to minimize physical impacts and disruption to recreation
activities and maintenance operations at Gene Coulon Memorial Beach Park and at
the Park Maintenance Facility; and
- to construct upland portions between Oct 15'h and March 1'st
♦ To minimize disrupting access to the Park by Park users, construction of the portions
of the Johns Creek Outfall in the vicinity of the Park will occur during periods of low
Park use (between October 15th and March 1S) except where limited by State and
Federal permits; and
- to start construction of in -water structure after July 4th weekend
♦ To minimize disrupting access to the Park by park users. When construction activity
which must occur during high -park use periods due to State or Federal permit
conditions, such activities will occur after July 4th weekend and not during Renton
River Days; and
to keep access open to Maintenance Facility between 5am and l 1pm
♦ To minimize disrupting access to the Park Maintenance Facility, construction
activities impacting access to the Maintenance Facility will occur during periods of
low Park use (between October 15th and March 1S) and will occur so that access to
the Maintenance Facility is available during maintenance staff work hours (between
5AM and 11 PM) and
- to maintain security at the maintenance facility during construction
♦ To provide and maintain security of maintenance facility during night work
conditions when existing security measures are adversely affected by construction
activities.
Protection of Plant Materials
- to avoid impacting median planters and plant materials
Attachment 1 page 4
Johns Creek Outfall
♦ To avoid impacts to the Park's natural resources and plant materials, measures will be
implemented to protect valuable plant materials within existing median planters on
Park roadways. Measures will include prohibition of machinery operation in planter
areas, prohibition of stockpiling in planter areas, protective fencing around planter
areas during construction, and other measures agreed to by both parties during
development of final design; and
- to avoid removing trees
♦ To avoid impacts to the Park's natural resources and plants, no mature trees will be
removed within the Park and substantial measures will be implemented to protect
mature trees adjacent to the outfall route. Measures will include establishment and
fencing of an exclusion zone around existing trees, prohibition of any construction
related activity within the exclusion zone, and other measures agreed to by both
parties during development of final design; and
- to confine construction disturbance to asphalt areas, where practicable
♦ To avoid impact to the Parks natural resources and plant materials, all construction
activity will be confined to areas of existing asphalt paving where practicable.
Construction of the outfall itself will necessitate work on the stream bank within the
Park Maintenance Facility, and will not be confined to asphalt paving areas; and
-
to restore disturbed areas
♦ To restore all disturbed areas including asphalt, mulching, landscaping, fencing, etc.
to pre -project conditions at completion of construction; and
- to verifydesign accommodates anticipated improvements in the Basin
♦ To minimize reconstruction of the outfall, the final design shall verify that the outfall
system accommodates future City and private improvements that are known by the
City at the time of the final design.
To address other impacts as: identified
♦ To minimize park impacts as required.
Construction outside of WSDOT I-405 ROW
♦ To minimize impacts to traffic, adjacent business and property owners when
constructing the Johns Creek storm water conveyance system outside of WSDOT
ROW, WSDOT will provide coordination with property owners and business and
provide for approval by the City a traffic control plan; and
♦ Be responsible for any and all Utility relocates that may be required, the acquisition
of any easements or property rights required for the construction of the Johns Creek
stormwater conveyance system that are not covered by existing WSDOT permits or
agreements (any Betterment for Utility to be by the Utility owner), and provide full
and complete restoration of the construction area to existing (pre -project) conditions.
Permits from other agencies are required
♦ The final design and construction of the proposed Johns Creek Outfall is dependent
upon the results of the environmental review (SEPA/NEPA) and WSDOT obtaining
the required approvals and permits from all appropriate local, state and federal
agencies, including grant agencies
Attachment 1 page 5
Johns Creek Outfall