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