Hungry Hollow Road Improvements
The Navarro Watershed Restoration Plan identified three goals for improving fishery and water quality: 1) increase frequency and depth of pool habitat; 2) decrease summer stream temperatures; and 3) reduce accelerated sediment production. One case study is the Hungry Hollow Road where road treatments were implemented in two phases, over a period of four years, to reduce sediment production.
Where is Hungry Hollow Road?
Hungry Hollow Road is located in the Mill Creek sub basin, a third order tributary to the mainstem Navarro River. The Mill Creek-Navarro River confluence is about 4 miles downstream of the town of Philo. Mill Creek watershed covers approximately 12 square miles.
Hungry Hollow Road is a spur off Clow Ridge Road, off the larger Nash Mill Road network accessed by turning north off State Highway 128 between the towns of Philo and Navarro in southern Mendocino County, California. Hungry Hollow Road originates on the north side of Clow Ridge and is approximately 2 miles long. The road declines in elevation from Clow Ridge tending east at a grade of about 8% for about1 mile. The second mile along the riparian snakes back and forth across Mill Creek before becoming impassable due to cutbank and fill failures beyond the last actively used driveway.
Why Make Improvements?
Mill Creek is used for spawning and rearing by anadromous salmonids, including steelhead-trout and coho salmon. After they lay their eggs, if the eggs hatch, the fingerlings develop according to the availability of cover and food before moving downstream to the Navarro River Estuary where they bulk up before entering the Pacific Ocean. This delicate life cycle is easily compromised from the degradation of habitat. Habitat degrades when fine sediment becomes embedded in gravels where anadromous salmonids spawn. Prior to 2000, Hungry Hollow Road contributed more fine sediment, and had a greater potential of contributing fines through stream crossing failures, than it does today. Historically, Hungry Hollow Road collected and concentrated road drainage. Stream crossing structures were inadequately sized, designed and constructed to handle large storm events. Today, Hungry Hollow Road is drained, well and frequently, onto stable surfaces. Stream crossings are diversion proofed, crossings are designed to pass fish, where appropriate, and crossings are sized, designed and constructed for the large episodic event.
A Brief History since 2000
In 2000, the first mile of Hungry Hollow Road was upgraded to which the California Department of Fish and Game contributed $25,000 and the stakeholders contributed $1,500. The work encompassed replacement of undersized and poorly placed culverts; elimination of diversion potential at culverts; and modifying road drainage through outsloping, elimination of outboard berms, and installation of rolling dips. Following completion of road shaping, treated areas were rocked as necessary to restore the road surface to its former condition.
In 2003, the second mile of Hungry Hollow Road was upgraded to which the California Department of Fish and Game contributed $32,963. The stakeholders contributed $2600. The work encompassed reshaping (outsloping with rolling dips); upgrading crossings, improving drainage and installing rock in a few key locations.
In 2004, $1,500 was spent maintaining and upgrading the surface of the road on the first mile of Hungry Hollow Road. In the same year, $3,275 was spent maintaining and upgrading the surface of the road on the 2nd mile of Hungry Hollow Road. No maintenance was commissioned in 2005.
To learn more about specific treatments you can go to www.nwwg.org, click on Community Workshops, click on Tree Tips and click on Roads.
Hungry Hollow Road Put to the Test
One thing that you can count on is change. Since the work was completed in 2003, traffic and year round use of Hungry Hollow Road has increased, the wettest December in at least 70 years transpired, destructive driving during wet conditions took place, the pulled back bank above the culvert inlet at Red Hill Gulch continues to fail and a large slide beyond human influence blocked the Road in the last 1/4 mile and continues to move. At the end of April 2006, the combination of these developments lead to a road nearly impassable to two-wheel drive vehicles in the first 1/4 mile of its length, definitely impassable for the last 1/4 mile of its length and passage of fine sediment into Mill Creek from the slide was obvious.
Overall, despite these challenges, none of the stream crossing upgraded in 2000 and 2003 failed during the 25 year storm event of December 30, 2005 and the uneven road surface, which had developed as soft spots were worked with vehicles, was remedied by a heavy grading. The heavy grading reestablished a smooth surface over the rolling dips and outsloped shape that had been established in 2000 and 2003. However, given Hungry Hollow Road has never had adequate rock applied to support the year round traffic, stakeholders will see surface problems develop again. Cost makes rocking the road prohibitive at this time.
The Forest and Ranch Roads Handbook describes the following surface treatment of all weather use roads. Angular rock should be placed to a total depth of 6-10 inches or more, then compacted to a finished depth of 4 to 6 inches, the base should consist of pitrun and makeup approximately two thirds of the depth, the upper 1/3 of the depth should be inch and a half and have enough dirt to seal the layer (Forest and Ranch Roads Handbook, June 1994). Pitrun is a mix of rock, including fines and large rock, which can be walked in by a heavy equipment to form a hard road base.
When the number of vehicles using the road exceed a certain point further treatment may be necessary to maintain the integrity of the surface. The neighboring Holmes Ranch measured use of the road network year round at over 80,000 vehicles per year. They have implemented further treatments which are described in the article entitled "Erosion Control for Roads, Our Experience at the Holmes Ranch Association" written by Fred Martin.
Road drainage, bank instability and contrived stream configuration contributed to the erosion at the Red Hill Gulch crossing. It is anticipated that Red Hill Gulch will be reworked this year, the route of the watercourse will be changed and the crossing moved such that the eroding bank will no longer be directly contributing sediment to the watercourse. In addition, road drainage will be redirected to a stable location such that it will not erode the culvert inlet and outlet fill. The California Department of Fish and Game has expressed willingness to fund the work.
The large slide that has made Hungry Hollow Road impassable for the last 1/4 mile is a very large feature that continues to move. To learn more about this feature you can go to www.nwwg.org, click on Resources, click on Tree Tips and click on "Beyond Human Influence".
Entities that made Improvements to Hungry Hollow Road Possible
The landowners provided access, contributed financial support, labor and will continue to bear the responsibility of maintaining Hungry Hollow Road. Danny Hagans of Pacific Watershed Associates conducted the road inventory in 1998 and supervised on the groundwork in 2000 and 2003. Dean Titus and crew, and Troy Bloyd did the work. Patty Madigan, Navarro River Watershed Coordinator, as an employee of the Mendocino County Resources Conservation District, coordinated efforts. Dan Sicular and myself, Thembi Borras contributed to the development of the grant proposals. The California Department of Fish and Game funded the bulk of the work. Russ Emal and I interpreted the work into a video. The Mendocino County Water Agency monitored Mill Creek water quality pre treatment and continues to do so post treatment.