Smith Creek Culvert Replacements & Riparian Planting Project

Project Summary

During the Summer of 2004, the Tillamook Estuaries Partnership (TEP) implemented two culvert replacements and over one half mile of riparian enhancements. Located on Smith Creek, a tributary of the Nestucca River on Oregon's northern coast, the two new culverts restored access to 1.5 miles of native salmon spawning and rearing habitat in the Siuslaw National Forest, restored sediment routing processes throughout Smith's lower reaches, and dramatically decreased non-point source bacterial loads entering the creek.

Private Culvert

The first culvert is located 0.5 miles upstream from the mouth of Smith Creek and serves as a cattle crossing to a dairy pasture. It was undersized and completely plugged with sediment, which forced water to run over the crossing, flood the adjacent pastures, and increase bacteria loading to the creek. This culvert was replaced with a larger pipe arch culvert that simulates natural stream conditions, thereby restoring fish passage and reducing bacteria loading.

Private culvert crossing before project implementation

Private culvert crossing after project implementation

Gist Road Culvert

Just upstream from the private culvert at stream mile 0.6, the Gist Road culvert lies under a Tillamook County road. Like the private culvert, it was undersized, but also had a slope of 4% and a vertical drop of 3.5'. These conditions completely restricted fish passage. This culvert was also replaced with a larger pipe arch culvert that restored fish passage.

Gist Road outlet before project implementation

Gist Road outlet after project implementation

Riparian Enhancements

From the mouth of Smith Creek, upstream to the Gist Road culvert, the riparian zone was dominated by reed canary grass. Over one half mile of native trees and shrubs were planted throughout this reach. Fencing setbacks were increased on existing fencing near the mouth.

This project was undertaken as part of a broad watershed restoration effort involving 17 partners, thereby ensuring that the entire length of Smith Creek--from the lowland pastures into the Siuslaw National Forest--provides quality fish and wildlife habitat.

Watershed Issues

Smith Creek, a tributary to the Nestucca River, drains 735 acres within the Nestucca River Watershed. About 15% of the streamside land use within this drainage area is pasture and 85% is forest. Smith Creek contains over two miles of spawning and rearing habitat for coho, chum, steelhead, cutthroat, and lamprey. Smith Creek meanders through dairy pastures at a relatively flat gradient (1-2%) up to Gist Road at stream mile 0.6 before entering Siuslaw National Forest land approximately one mile upstream of the Nestucca River. Above Gist Road, the stream gradient is estimated to average 2-3% for about 1.5 miles until steepening into the stream's headwaters.

Private Culvert

The culvert plugged the creek and created an overflow channel
Click photo to enlarge

The 2' x 27' culvert, located at river mile 0.5 on Smith Creek, was used as a cattle and equipment crossing on a privately-owned dairy farm. This culvert was an undersized, failing, corrugated steel culvert so completely clogged with sediment, water was forced to run over the cattle road.The prior owner of the farm ditched Smith Creek and installed a culvert crossing for road access to pastures on the other side of Smith Creek (primarily for manure trucks and dairy cows). When the new owner had attained the property, the creek had accumulated so much sediment that the culvert was completely buried.

During large rain events, the creek floods the whole pasture and flows in a shallow sheet across the dairy fields and down the pasture access road directly into the Nestucca River and Bay. The conditions caused by this culvert created a fish passage barrier at low stream flows, and washed manure directly into the creek during high flows, causing significant water quality degradation to Smith Creek and the Nestucca River. (The Nestucca Bay is currently listed under Section 303(d) of the Clean Water Act for elevated levels of bacteria.)

Gist Road Culvert

The old culvert at the Gist Road crossing was a 50' long, 4' diameter concrete culvert with a 4% slope and a 3.5' vertical drop from the outlet to the downstream plunge pool. The culvert restricted downstream bedload transport of sediments which led to frequent sediment blockages on the upstream end, and lack of sediment recruitment to downstream reaches. The culvert's 4% slope increased water velocities, thereby impeding fish passage. In addition, part of the culvert broke off and fell into the pool below. According to Oregon Department of Fish and Wildlife (ODFW) personnel from the Tillamook field office, the 3.5' drop, steep slope, and broken culvert prohibited fish passage at all times. In a July 1965 ODFW survey, juvenile coho were found in the upstream habitat. No redds were found above the culvert during the winter ODFW 2001 spawning surveys.

Several options to address the Gist Road fish passage barrier were considered during the development of the engineering plans. With consultation and field visits among Otak Incorporated (licensed engineering firm), ODFW, TEP, Nestucca-Neskowin Watersheds Council (NNWC), and Tillamook County Public Works Department (Public Works), an oversized embedded pipe arch culvert with adjacent rock weirs was selected as the best replacement alternative. Other options considered included a bridge and an open-bottom arch culvert. These options were not selected because the ecological and hydrologic benefits were not significantly different than the selected approach and design and construction costs would have roughly doubled.

Riparian Enhancements

From the mouth of Smith Creek upstream to a bridge between the Private and Gist Road culverts (0.55 stream miles), livestock are excluded from accessing the creek access with fencing (setback distance varies from 3-10'). Reed canary grass had invaded the stream banks and restricted channel water flow. Little native vegetation existed, except for a few willow trees. Increasing fencing set backs and establishing a "healthy" riparian area will stabilize the stream banks, reduce sedimentation and stream temperatures, and improve bacteria/nutrient filtering from adjacent pastures.

Project Implementation

This project was implemented in two phases. Phase I of the Private and Gist Road culvert replacements and riparian enhancements involved completing designs, signing MOU's between stakeholders, and securing permits, construction easements, and funds for Phase II. The following describes the activities associated with the implementation of the three projects.

Private Culvert, Phase I - Project Design

An NRCS engineer designed a culvert replacement for the cattle crossing. Stakeholders signed MOU's, and TEP secured permits, construction easements, and funds for Phase II.

Private Culvert, Phase II - Culvert Construction

The creek, directed from the overflow channel back into the original channel

Implementation of the design replaced the existing 2' x 27' culvert with an embedded, 81"x59"x20' corrugated metal pipe arch culvert. It was designed and sized to accommodate the unrestricted passage of water, fish, and bedload materials during any flow, restore stream channel stability, and simulate natural stream bottom conditions. The installed culvert slope was 0%, which increased to 1.6% as planned after the first rain event to match the newly excavated channel slope. The existing road surface was elevated 4', accommodating the new culvert and preventing bacteria from entering the creek when the livestock use the crossing.

The existing channel bottom was excavated through sediment deposits to facilitate water confinement within the channel and decrease its interaction with adjacent fields. The average excavation depth was 2' with a total excavation volume of 220 cubic yards. Excavated materials were used to construct low berms on both sides of the channel, approximately 3' wide and varying in height from 1-3'. The berms limit the channel's floodplain interaction, which would otherwise routinely flood onto adjacent dairy pastures. 400' of existing channel was disturbed, and the channel width mirrors existing upstream and downstream conditions.

Three log x-weirs were installed below the new culvert at 99', 221', and 338', to control stream grade, minimize incision and bank erosion, and provide instream habitat for salmon. The top log, with an intact rootwad, was anchored to the lower log to ensure stability.

Gist Road Culvert, Phase I - Project Design

Phase I hired OTAK Incorporated, who created engineering designs for the culvert replacement. Stakeholders signed MOU's, and TEP secured permits, construction easements, and funds for Phase II.

Gist Road Culvert, Phase II - Culvert Construction

Below Gist Road culvert around summer flows

Utilizing OTAK's engineering design, TEP replaced the current 50', 48" diameter concrete culvert with a 66' long, 128" x 83" diameter 12 gauge aluminized steel type II corrugated pipe arch culvert. The new culvert width is greater than the 8' average stream width throughout the project reach, which will deter channel constriction conditions. The culvert has a 1.3% slope and is embedded approximately 18" into the stream channel, simulating a natural stream bottom. As recommended by Jane Kelly, ODFW Fish Passage Engineer, a series of rock weirs, two upstream and three downstream, were created to provide streambed grade control and allow the culvert to have a gentle slope and slower water velocities. Three shadow rocks between 15" and 18" were buried a minimum of 1' throughout the culvert with 6" of the rock exposed and stabilized with smaller boulders. These rock clusters further contribute to decreased water velocities.

A temporary sandbag dam and diversion pipe was installed in the construction area. The engineering plans included an erosion control strategy that was strictly adhered to. All in-stream work followed ODFW's publication "Oregon Guidelines for Timing of In-water Work to Protect Fish and Wildlife Resources".

Riparian Enhancements

Riparian plantings (notice metal cages)
Click photo to enlarge

TEP collaborated with the NNWC to implement one half mile of riparian enhancements. In April 2003, riparian areas on both sides of Smith Creek were cleared of reed canary grass and planted with native trees and shrubs (460 trees protected with metal cages and 1200 willows). These trees were maintained during the summer months in 2003 and 2004 to ensure their survival. During the summer of 2004, 250' of existing fencing on the east side of the channel at the mouth of Smith Creek was adjusted to increase the setback distance from 3-10' to 10-12'. All remaining areas to be planted (around the two culvert replacements and at the mouth within the new fencing setback) will be planted by the end of this month (December 2004).

Overall, the project had six primary goals:

1) Expand access to salmonid spawning and rearing
    habitat in Smith Creek by 1.5 miles.
2) Dramatically reduce non-point source bacterial contamination of Smith Creek.
3) Re-introduce chum populations to Smith Creek.
4) Establish a "healthy" riparian area over 1/2 mile on both sides of Smith Creek.
5) Establish an ongoing partnership between local watershed enhancement groups and Public
    Works in order to address fish passage barriers on County roads.
6) Demonstrate to the local community the benefits and effectiveness of subbasin restoration
    efforts.

By implementing all three project components within two years, we demonstrated to the community the effectiveness of a holistic sub-basin restoration effort and saved money on the construction elements of the project.

Partner Coordination

This project represents a collaborative effort to restore fish passage and improve water quality conditions on Smith Creek, a significant tributary stream of the Nestucca River, Oregon. Smith Creek drains 735 acres within the Nestucca Watershed and is largely within the boundaries of the Siuslaw National Forest. Planning for this project was undertaken by a large group of 17 interested stakeholders providing expertise and technical assistance, including:

• Tillamook Estuaries Partnership: overall leadership; fundraising; partner coordination; permitting; project management; contract administration
• National Forest Foundation: funding
• NOAA Fisheries: funding
• Oregon Watershed Enhancement Board: funding
• Oregon Department of Environmental Quality: funding
• Oregon Department of Fish and Wildlife: funding; technical assistance
• Tillamook County Creamery Association: funding
• 4 Private Landowners: construction easements; cooperation
• Tillamook County Public Works: construction management of the Gist Road culvert; technical assistance
• Nestucca-Neskowin Watersheds Council: community outreach; monitoring; riparian restoration work
• Siuslaw National Forest: cooperation; support
• Tillamook Native Plant Cooperative: native trees and shrubs for riparian restoration
• Natural Resources Conservation Service: engineering design; construction management of the Private culvert
• Tillamook County Soil and Water Conservation District: fencing set back adjustments

Monitoring and Evaluation

Project success will be determined based on the following indicators:

1) The presence of fish from the mouth of Smith Creek upstream into federal forest lands;
2) A reduction in non-point source bacterial contamination;
3) The performance of two new culverts simulating natural stream bottoms and providing for
    downstream gravel migration;
4) The recruitment of gravel downstream of the blocked culvert;
5) The successful growth of planted native riparian vegetation as a replacement for invasive reed
    canary grass; and
6) Projects initiated in neighboring watersheds.

Assessment

Project results met the expected results. Long-term monitoring will ultimately determine whether or not the project is successful. Thus far, however, the project has been a success. The two culvert replacements restored fish passage, and monitoring will determine if fish populations re-distribute into upstream reaches that were inaccessible. The source of bacterial contamintation, the Private culvert, is eliminated. Riparian area enhancements have begun to establish "healthy" riparian areas, but monitoring will determine the long term survival.