2015-2017 DOE Floodplain Mgmt Project Preliminary ProposalNM WASHINGTON STATE
DEPARTMENT OF
ECOLOGY
2015-2017 FLOODPLAIN MANAGEMENT PROJECT
PRELIMINARY PROPOSAL
The Washington State Department of Ecology is soliciting Preliminary Proposals for inclusion in the
agency's budget request for fiscal years 2015-2017. Preliminary Proposals will be used to choose
projects that will be asked to prepare detailed proposals for inclusion in Ecology's budget request.
(Those more detailed proposals will be due August 1, 2014.) While Ecology cannot guarantee
legislative action, requesting continued funding for this program is a high priority for Ecology and
other partners. Ecology anticipates submitting a request for no less than $50,000,000 for these
projects.
Preliminary Proposals must be submitted electronically via email to Ecology by 5:00 p.m. May 23,
2014. Send Preliminary Proposals to:
Charlena Hall at Charlena.Hall@ecy.wa.gov
With the Subject Line: Floodplains by Design Preliminary Proposal
Project Title: Chester Creek Floodplain Mitigation Plan
Organization Name: City of Spokane Valley
Contact Name: Art Jenkins
Address: 11707 E. Sprague, Suite 106
Phone: (509) 720-5018
Spokane Valley, WA
Email: ajenkins@spokanevalley.org
City, State, Zip: 99206
1. Project Description:
Background:
Chester Creek runs south to north and drains approximately 23 square -miles of mostly undeveloped basin with steep
hillsides to the south and a more urbanized flood plain in the north. Elevations range from 3,650 to 2,000 feet. Chester
Creek is an unusual stream system because at its end (less than 2 miles to the north) it infiltrates entirely into the soil,
and ultimately, the Spokane Valley — Rathdrum Prairie Aquifer. The creek enters the City of Spokane Valley from
Spokane County at Thorpe Road. The area south of Thorpe Road in the county is experiencing steady residential
development where residential lots front the edge of the floodplain along Chester Creek.
Historically, Chester Creek fanned out across the flood plain in the lower watershed (Figure 1). Early farmers formed
berms to contain the stream within the present-day channel, but the berms have not been maintained. Parts of the
berms have deteriorated, and now, during spring runoff and the occasional cloud burst, Chester Creek overtops the
berms and floods property to the north and east.
Most of this property is open meadow, marshland, and to the north of Thorpe Road, the Painted Hills Golf Course. As
the economy has improved, the area is attractive to people who want to live in an area where there is open space and
aesthetic benefits that add to the quality of life. Several small businesses operate along the Chester Creek drainage,
businesses that have larger pole barn shops, and places to store materials and equipment. Examples include landscaping
and contracting businesses.
FLOODPLAIN BY DESIGN
TARGET AREA
City of
Spokane
Valley
Thorpe Rd
Spokane
County
CHESTER CREEK
WATERSHED
Madison Ra'
05 0 1 Mile
Figure 1
Chester Creek Watershed
Until recently, each year during periods of high water, Chester Creek overtops the berms, and water moves to the east
and flows over Thorpe Road. To the west, the Thorpe Road Bridge provides a place for water to go safely under the
road, but in times of heavy run-off, a significant quantity of water bypasses the bridge and drains into the golf course. At
times, when Thorpe Road is flooded, the road was closed. Two years ago, the City of Spokane Valley replaced 3 — 15"
culverts to provide drainage under Thorpe road. Since installing the culverts, water hasn't overtopped the road at the
eastern location, but continues to overtop each year just west of the bridge.
There are several wetlands along the riparian corridor. These wetlands sit to the south and west of the Thorpe Road
Bridge. The City and County have tried to keep the wetlands healthy by providing drainage via a fabric -lined, rocked -in
spillway that drops into a depression just south of the bridge; however, during times of heavy run-off, the water volumes
increase to the point where it erodes the spillway.
In 1995, Spokane County hired a consulting engineering firm to assess the current condition of resources in the
watershed and evaluate how they may be affected by land use practices. The goal at that time was to develop a sound
management plan for the watershed that provided cost-effective and long-lasting solutions, natural and structural, to
flooding of roads and property.
The plan worked to identify capital improvements that provided efficient drainage and good storage for water retention
to prevent flooding, enhance water quality, while still providing a healthy wetland and riparian habitat. Due to the
County's watershed planning effort from 1995-1997, projects identified in the watershed plan north of Thorpe Road
were completed. For example, the County installed new culverts and extensive channel clearing of Chester Creek
between Thorpe and Schaffer roads. Additionally, as part of a Spokane County improvement project for the Dishman-
Mica Road, a large volume retention pond was constructed along the west side of Dishman-Mica Road which was
designed to act as a retention and infiltration facility for the floodwaters of Chester Creek.
Scope of Work:
From the original watershed plan completed in 1997, the work identified has been completed north of Thorpe Road. In
the original plan, the work south of Thorpe Road was never completed. The work identified in the original plan was to
preserve the original berms and clear the channel of large trees and debris, and clean out the exiting culverts at various
Chester Creek private road crossings. Emphasis on the original watershed plan was to maintain the existing creek
channel to preserve the investment in the original Thorpe Road Bridge.
Grant funds will be used to preserve the existing creek channel by maintaining the existing berms. The berms will
require inspection, testing, and where the structural integrity is deficient, berms rebuilt.
Over the years, what appears to be a healthy wetland has developed south of Thorpe Road, south and west of the
Thorpe Road Bridge. This wetland is a little over 13 acres and has a healthy community of birds including ducks and
songbirds, whitetail deer, raccoons, etc.
Funds from this grant program would be used to update the original watershed plan by Spokane County in 1997. This
update would include a hydrologic analysis to measure inflows and outflows of ground and surface water, the resulting
water levels, and the timing and duration of soil saturation or flooding. After determining the water and soil
characteristics for the wetland, a plant inventory will be taken to see what existing plants are contained in the wetland.
The inventory will be used to determine which plants should be encouraged to remain, which plants may be nuisance
species and should be removed, and what new plants should be added and where.
Upon the results of the study, wetland project design will be pursued to establish the capital improvements needed to
maintain the wetland. These improvements may include spillway design from the wetland to the pond below the bridge;
the addition of new dikes or culverts, and wetland plantings. Also, the plan would give guidance on items like wetland
excavation in order to insure that the deepest part of the basin is below the lowest anticipated water level.
The update of the original watershed plan will also include going back and evaluating the original limits of the study to
determine how effective the improvements north of Thorpe Road have been since being constructed back in the late
nineties and early two thousand.
2. Estimated Budget:
The source for the City of Spokane Valley matching funds would come from the Stormwater Utility fund reserves and/or
Aquifer Protection Area fund reserves.
Update the Watershed Plan by Spokane County in 1997: $120,000
Engineering, Preliminary Design and Construction Inspection: $97,500
Berm Inspection and Testing: $60,000
Rebuilding Berm Sections: $220,000
Channel Clearing: $110,000
$607,500
Since becoming a city in 2003, Spokane Valley has managed several complex projects. Because of the way the city is
structured and managed, with an emphasis on few full-time employees, the city has a staff made up of seasoned
professionals who can direct and manage consultant studies and designs. And, once the design is complete, the city
again has seasoned professionals who understand the work and know how to administer construction contracts to get a
completed project to conform to the intent of the original design.
Amount requested from Ecology
$ 486,000
Non -state matching funds, including source
$ 121,500
Total Project Cost
$ 607,500
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