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Clean air,
natural surroundings, clear lakes and streams are all critical to
preserving Redmond's natural resources and maintaining our high quality
of life. Redmond has actively worked to meet lake and stream water
quality standards that insure our water is:
Safe for human contact, healthy for fish and animals, compliant with state water quality regulations,
and aesthetically pleasing. The Natural Resources Division
monitors our water quality, designs and implements stream improvements
and stabilization projects through the Stormwater Utility funds. The
ever-growing public demand to maintain high water quality standards, and
regulations in the
Clean Water
Act Regulations and the endangered species listing of the
Chinook salmon,
requires an extensive monitoring of our city's lakes and streams.
If you would like more information on the quality of Redmond's lakes and streams,
please e-mail us at nr@redmond.gov.
The Natural Resources Division is currently working on stream
enhancement projects such as the Upper Peters Creek Streambank
Stabilization Project.
Peters Creek is located on the west side of the City and discharges
to the Sammamish River. Most of Upper Peters Creek watershed was
developed prior to modern stormwater quality and detention requirements.
The lack of stormwater controls in this basin led to bank erosion and
channel incision. Previous uncontrolled stormwater flows destabilized
the creek's banks, incised the creek bottom, eroded significant amounts
of material, and eliminated salmon and trout.
Due to the erosion in upper Peters Creek, city staff identified the
need to divert the highest peak flows away from Peters Creek and into a
receiving water body that could handle the flows without eroding the
streambanks. In 1996, a pipeline was built to divert uncontrolled
stormwater flows out of Peters Creek and directly into the Sammamish
River. This diversion appears to have eliminated new erosion in upper
Peters Creek, although banks undercut from previous uncontrolled
stormwater flows continue to collapse into the creek.
Historically Peters Creek has supported a modest Coho salmon run and is
currently used by both juvenile and adult Coho and Chinook salmon and
cutthroat trout up to the culverts under Redmond Way. The culverts at
Redmond Way on both the main and west branches are impassable to fish.
During the construction of the access road, Piliated woodpeckers were
seen in the ravine. A professional biologist surveyed the site for
Piliated woodpeckers and habitat for other state priority species. No
nesting or foraging Piliated woodpeckers were observed during field
visits by professional biologists; however, two recommendations were
made: (1) construction activities should take place outside of nesting
season (mid-March to mid-July) and (2) removal of trees over 12"
diameter should be minimized.
The goal of the project was to stabilize a portion of upper Peters
Creek in a habitat friendly manner. The primary goals of the project
included the following:
- Stabilize the creek channel and streambanks using materials
naturally occurring in the stream such as wood and rocks.
- Enhance the area for aquatic and terrestrial habitat.
- Improve downstream habitat and flooding concerns by reducing the
amount of sediment exported downstream.
Approximately 1,500 feet of stream improvement was completed using
multiple restoration techniques including logging crews using sky-line
cabling systems, traditional heavy machinery, and hand labor utilizing
specialized tools.
Phase I of the channel improvements was constructed in 1999 using city
stormwater maintenance crews. It began at approximately 7031 NE 151st
Street and ended at the north property line at 7050 NE 150th St.,
approximately 500 feet.
Phase II was constructed during the summer of 2003, again using City
crews. It began at the north terminus of Phase I and continues to the NE
76th St. right-of-way, approximately 700 feet.
The following steps were taken to prevent erosion:
- A temporary diversion system was installed upstream of the project
with an in-stream bentonite dam with four submersible pumps.
- Construction in the ravine was limited to only 6 weeks in the
driest part of the year (July 15th to August 30th).
- The entire creek bottom was covered in plastic, construction
ceased, and the stream was gravity fed through the site in a flexible
pipe capable of handling 100-year storm whenever a rainstorm was
forecast.
- A temporary in stream sediment pond was excavated at the end of
the project site with two quarry spall check dams for filtration. All
streamflow did not exhibit any turbidity at the outflow of the project
during construction.
- The banks where hydroseeded with native grasses, and hand seeding
of native grasses replaced some areas where the hydroseed was
trampled.
Bank Stabilization and Stream Improvement Features
The over-excavated channel banks where reconstructed using a
combination of rounded boulders, rootwads, logs, and packing with fill
material. Stream gravel was placed on top of the fill. Logs were placed
in the banks as both low and high flow deflectors. Rock weirs and log
grade controls were placed on average of every 50 feet. Rootwads where
placed strategically throughout the system both to create roughness, to
deflect flow, and to create habitat. The existing tree canopy should
eventually provide additional wood into the stream system by falling
naturally.
Approximately 450 native trees and shrubs where installed. Over 500
plants are planned for Phase II. After the initial planting establishes
and an organic top layer develops, it is recommended another planting be
conducted in 5-8 years to further enhance the diversity of plants along
the banks of the stream.
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