Washington, in the great Pacific Northwest, is one of the nations leading states in environmental concerns. Included in these concerns are the areas of erosion control, water contamination, silt build up and flooding. All these concerns have a serious effect on a bigger picture of the environment, which is fish and wildlife.

Northwestern Landscape Company, located in the Seattle area has been involved in habitat and stream restoration and erosion control for nearly 20 years. The company successfully built and constructed projects for the University of Washington's Bothell Co-located Campus (UWB/CCC).

University of Washington's Bothell Co-located Campus

Water for the irrigation system is pumped from the original stream.

The UWB/CCC project is visible from the intersection of one of the busiest freeways in the Seattle area. This project is highly controversial being one of the largest projects of its type west of the Mississippi River.

The site consists of approximately 58 acres of disturbed wetland. The site also includes 3,200 feet of the North Creek channel, the historical flood plain of North Creek and hill slopes that are part of an old recessional moraine. Wetlands occur both in the flood plain and along the hill slopes. The portion of North Creek that flows through the site has been straightened and confined within artificial levees.

In planning the development of the campus on this site, a number of principles were followed. These included: adherence to all regulatory requirements; targeting no net loss of wetland area and/or function through a program of avoidance, minimization, and then mitigation; targeting an

on-site approach to wetland mitigation; and mitigating for native riverine ecosystem functions and features based on standards obtained from regional reference sites.

Screens were installed to prevent fish from entering the irrigation pumps.

For the state to construct the new campus, mitigation consisted of on-site restoration of waters/wetlands functions to approximately 58 acres of riverine channel and valley alluvium, since the potential for restoring a higher level of functioning to this system was high. By undertaking the restoration of North Creek and its associated flood plain on the site, the state was able to meet its mitigation requirements for development of the campus and also provide long term environmental and educational benefits to the citizens of the state.

The restoration design is based on historical information, reference data from similar stream ecosystems in the area, information from the existing North Creek channel, both on-site and upstream, and best professional judgment of the scientist and engineers involved in the design. Overriding design objectives were to reconnect North Creek with portions of its historical flood plain, restore natural stream morphology to the channel, reintroduce large wood to the system, restore native plant communities to the flood plain, and provide improved habitat for aquatic and terrestrial wildlife species.

Construction Begins

Three tier erosion control fencing is set up to prevent contaminants in the flood plain.

Construction of the restoration was phased over a four year interval. Beginning in the summer of 1998, the majority of the site was stripped of weeds and graded, the new channel was graded and large wood was placed along the channel and in the flood plain. Planting began in the fall of 1998 along the banks of the new channel, and continued over the next three years until the whole site was planted. Stream flow is gradually being introduced to the new channel to allow the new channel to adjust. Transfer of flow from the old channel to the new channel will be completed in year four, and the old channel will be filled and graded.

Some of the erosion challenges during construction were solved by job specific creativity. To accommodate straw blowing over the entire site, which is in muddy stages even during summer months, a special cart was designed with balloon tires. This cart held a small straw blower. The cart was pulled manually by 4-6 crew members throughout the site, as there were no other alternatives to distribute straw properly.

Irrigation Installation

A straw blower was used to treat the flood plains.

Two years prior to the opening of the new stream channel, silt fence was placed to line both sides of the existing stream channel to keep silt from contaminating the waters and causing a threat to the more than six fish species that spawn in the creek. The first year, erosion control covering established well and a 58 acre irrigation system was installed to insure coverage of vegetation during dry months.

The grasses in year two were all hand cut as no equipment was allowed on site to insure flood grades were unaffected. Conditions were prepared for shrub and rhizome plantings in year two. Conditions were so muddy that containers were pulled to the site on special roads constructed with a wide track dozer pulling a sled across the mud loaded with the planting material.

Restoration design is based on historical information, reference data from similar stream ecosystems in the area, and information from the existing North Creek channel, both on-site and upstream. Construction of the restoration was phased over a four year interval beginning in the summer of 1998.

The irrigation system pumps water from the existing stream channel and special screens are necessary to prevent fish from being sucked into the pump system.

The project was an overall success starting with the early stages of 58 acres of striped land and bare dirt to the completion of erosion control measures along the new stream channel. Protection of the existing stream from silt and fuel contaminants helped create a successful environment for the fish and wildlife habitat.

Thornton Creek

The original creek, had concrete weirs that were removed and the sites along Thornton Creek were demolished and rebuilt, to natural conditions. Twenty seven sites along the stream were renovated.

Thornton Creek is a stream channel winding through the northern part of the city of Seattle. This stream was severely environmentally damaged over the last 75 years. Through a city mandate and nationally supported measure, 27 sites along this stream were completely renovated and brought back to natural conditions. This included removal of concrete weirs and diverting of streams in heavy flood season. It also consisted of recreating stream banks with caution to prevent "washout" during the winter months. Efforts were made to encourage salmon spawning productivity in this creek, which had been reduced over the years.

The Construction Process

The sites were completely cleared and grubbed. Silt fence and drain rock was installed along the entire length of the creek areas affected. This helped to prevent loose soil from reaching the water. Water was diverted from two streams, and diverted through large tubes into one stream in a nearby location.

Large holes were dug into the existing stream channel and trees and logs were installed using Manta Ray anchors. Backwashes were dug into the stream for a holding place for aquatic life during construction. All aquatic life was removed with an aquarium fish net and moved to a safe downstream location as construction silt can be deadly to fish. The backwashes, which were 20' by 10' in size, generated much extra soil that was dispersed along the previously cleared areas.

Once the root wads and rock bottoms were in place (completely new stream channels consisting of different aggregate sizes were constructed) the dams constructed to temporarily divert water were removed and water was carefully introduced to the new stream channel. During construction some of the contaminated material removed from years of destruction included: old car bodies, refrigerators, water heater, grocery carts and tires. All water diversion techniques were government regulated and required a plan to be submitted for approval prior to construction activities.

Erosion Control and Sediment Issues

Log and root wads were installed to prevent washout, after concrete weirs were removed. Silt fence and drain rock was installed along the entire length of the creek areas affected. This helped to prevent loose soil from reaching the water. Water was diverted from two streams, and diverted through large tubes into one stream in a nearby location.

Because of erosion control and sediment issues, diversion consisted of constructing sand bag and filter fabric weirs downstream along with filters (wire mesh fences). The channels to divert water were constructed of PVC; concrete; plywood; and 2x4's. This was to keep water clean and free of sediment downstream. Quick set concrete was necessary so the pours would set quickly and not washout. Also, all slurry was covered with liners so no concrete could contaminate the stream.

Removal of existing rock gabion, some up to 4' in height and 150' in length had to be removed from the sites. These areas where gabion where removed were rebuilt with 18" caliper cedar logs and root wads. They were dug into the bank and then covered with 24"-36" boulders to prevent washout. Large amounts of 1 1/4" minus washed rock was placed in the stream to prevent soils from being washed down stream.

Any dirty water contaminated by sediment that did happen to make it downstream had to be trapped and converted into holding areas by using large pumps.

At one area of the creek a road was built through the water to gain access to rebuild a washed out area. An excavator entered the creek bed on this special road once all water was diverted. After jute netting, topsoil and live willow cuttings were installed in this washed out area as well as root wads and logs, the road was dismantled on the way out of the creek and the water was introduced again into the stream channel.

Much of the site consisted of 1 to 1 slopes, which required construction of temporary switch back roads. The roads were reconstructed with jute net and plantings to prevent hillside washout during winter months.

The Chutes

Some slopes were so steep and near existing homes that walls made of ecology blocks were constructed to make "chutes." These chutes were used to roll 30-plus inch boulders down more than 80 feet to the working areas. Also, aggregate material was diverted down the chutes. This allowed the importation of material in a safer manner without disturbing surrounding structures that had been

built near the sites over the last 50 years. Some water had to be diverted over 200 feet. To prevent wash out and

flooding problems, this water was diverted through temporary PVC structures.

The successful completion of the Thornton Creek restoration was applauded by the city and many community groups. Years of environmental damage was repaired at 27 sites along the creek, bringing it back to natural conditions, all the while maintaining safe water quality conditions during construction.