Implementing Sediment and Pathogen TMDLs in the North Bay: Napa River Watershed
Leigh Sharp, Executive DirectorNapa County Resource Conservation District
November 4, 2012
A Project of the Napa County Resource Conservation Districtin collaboration with North Bay Watershed Association and San
Francisco Estuary Partnership with funding from the US EPA San Francisco Bay Water Quality Improvement Fund
Napa River TMDL Information
• Listed for sediment, nutrients, pathogens
• TMDLs adopted for sediment and pathogens
• Sources of sediment– Channel incision & bank erosion,
roads, gullies, and sheet erosion– associated with vineyards, grazing,
rural lands, parks and open space, and public works
• Sources of pathogens – On-site sewage disposal systems,
sanitary sewer systems, municipal runoff, grazing lands, confined animal facilities
Major Project Tasks
Implement Sediment TMDL in Napa River Watershed– Conduct outreach– Complete rural road assessments– Implement road improvements in
Heath Canyon watershed
Implement Pathogen TMDL in Napa River Watershed– Conduct outreach and education to
land managers with confined animal facilities
– Implement identified projects to manage runoff & erosion
Coordinate with other NBWA partnersWatershed Monitoring
– Sediment and fisheries related monitoring
Roads influence the hydrology of a watershed
• Poorly constructed and maintained roads concentrate runoff, increase erosion, and potentially deliver sediments to streams
• Studies demonstrate that up to half of all anthropogenic sediment entering streams comes from road-related erosion
Accomplishments to Date: Road Treatments
Humboldt County
Excess sedimentation and increased runoff impairs stream function
May:• Pollute water
supplies• Increase potential
for flooding• Accelerate stream
bank erosion and trigger landslides
• Erode or harm riparian vegetation
Excess sedimentation impairs aquatic habitat
• Suffocates fish eggs in spawning beds• Loss of aquatic habitat
Our goal is to treat roads with practices that are safe for travel and most mimic nature
Nothing in nature mimics a road……but roads are necessary
China
Sediment delivery from road-related erosion can be episodic or chronic
• EPISODIC sediment delivery– Sediment delivery is episodic when it occurs as soils fail in response to
storm events or other triggers. The delivery from a site may occur once, or in pulses over an indeterminate time period. Stream crossing washouts, road-related landslides, and gullying can produce episodic sediment delivery.
• CHRONIC sediment delivery– Sediment delivery from road surfaces and cutbanks is chronic because it
occurs continuously during rainfall events that produce surface runoff
Culvert
Natural stream grade
Road fill
Road surface
Episodic sediment delivery results from poorly designed stream crossing
Aggraded sediments above inlets can cause crossings to wash out
Napa County
Channel scours below outletNapa County:
treated by RCD in 2009
Stream crossing fails and produces episodic sediment delivery
Napa County: treated by
RCD in 2009
Low impact design for a culverted stream crossing on a non-fish bearing stream
CulvertNatural stream grade
Road fill(2:1 slope)
Road surface (4% outslope)Trash rack
Fail-safe features impede plugging of culverts and prevent sediment delivery if crossing floods
Napa County: treatments in 2010
Examples from Heath Canyon Work
treated in 2011
Old culvert inlet
New inlet setat grade
Examples from Heath Canyon treatments
Old culvert outlet
New outlet set in at base of fill
Old culvert outlet
New outlet set in at base of fill
New inlet setat grade
Armored fill crossings may be
sufficient on seasonal-use
roads
Sediment delivery from road-related erosion can be episodic or chronic
• EPISODIC sediment delivery– Sediment delivery is episodic when it occurs as soils fail in response to
storm events or other triggers. The delivery from a site may occur once, or in pulses over an indeterminate time period. Stream crossing washouts, road-related landslides, and gullying can produce episodic sediment delivery.
• CHRONIC sediment delivery– Sediment delivery from road surfaces and cutbanks is chronic because it
occurs continuously during rainfall events that produce surface runoff
Fine sediments are generated as vehicles mechanically break down the road surface
This is what happens to that powdery dust when
it rains
Napa County
Physical features show surface lowering over time
Exposed culvert
Napa County: treated by RCD
in 2011
Shape of road surface can concentrate flow and promote erosion
Berm
Runoff
Before
Napa County: treated by RCD in
2009
Low impact road surface design disperses flow across the landscape
Ditchremoved Berm
removedRunoff
After
Rolling dip
OutslopingNapa County: treated by RCD in
2009
Examples from Heath Canyon Work treated in 2011
Runoff
Runoff
Rolling Dips
Road runoff from both roads delivering to a gully and a
stream
Road runoff from side road treated separately, runoff dispersed via rolling dips
(away from gully and stream)
Before
Runoff
After
Runoff
Rolling Dip
Preliminary Numbers
• 6,144 yd3 of sediment delivery to waterways avoided
• 4.71 miles of road treated
• 32 stream crossings upgraded
• 83 rolling dips installed
Napa County: No treatment needed
Use the right tool for the job
Napa County: RCD treatments 2009-2011
Plan for cultural resources too
Napa County: RCD Treatments 2011
Additional Funding Partners
• California Department of Fish and Game
• Napa County (Measure A)
• California Department of Conservation
• Private Landowner
Napa County: treatment by RCD in 2010
Next Steps……
• Complete additional road assessments
• Work with rural landowners with confined animals
• Develop more QAPPs