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Section 319
NONPOINT SOURCE PROGRAM SUCCESS STORY
Stakeholders Cooperate to Reduce Diazinon in Runoff from Dormant
Season Spray
fltPrhnrlipQ Imnrnx/pH WidesPread use of the organophosphate (OP) pesticides diazinon
VVdLWl UUUlWb II i ipi UVWU and ch|orpyrifos in California's Central Valley resulted in aquatic
toxicity in the Sacramento and Feather rivers and their tributaries, Sacramento Slough and Sutter
Bypass. As a result, in 1994 the Central Valley Regional Water Quality Control Board (CV-RWQCB)
added a 16-mile segment of the Sacramento River, a 42-mile segment of the Feather River, the
1.7-mile-long Sacramento Slough, and the 19-mile-long Sutter Bypass to the CWA section 303(d)
list of impaired waters. In 2001, the Sacramento River Watershed Program (SRWP) developed and
implemented a water quality management strategy for the two rivers, which included installing on-site
best management practices (BMPs). Diazinon concentrations decreased, prompting CV-RWQCB to
remove Sacramento Slough and Sutter Bypass from the CWA section 303(d) list in 2006. The state has
recommended the removal of the Sacramento River and Feather River segments (58 river miles total)
from the 2010 CWA section 303(d) list for diazinon impairments.
Problem
The Sacramento River is California's longest river,
flowing from Mt. Shasta to the confluence with the
San Joaquin River at the Sacramento-San Joaquin
Delta. The Feather River is the primary tributary to
the Sacramento River (Figure 1). The Sutter Bypass
is a floodwater bypass that diverts excess water
from the Sacramento River between two large
levees. It also provides for local drainage for the
Sutter/Butte Creek Basin. The Sacramento Slough
(Figure 2) serves as an outlet for the Sutter Bypass
to flow into the Sacramento River.
Orchard managers used diazinon for decades to
control wood-boring pests in the stone fruit and nut
orchards in the Sacramento/Feather River water-
shed. Diazinon is highly toxic to aquatic life, and
exposure to even low concentrations of the pesticide
(one part per billion or less) can cause genetic dam-
age in fish and reduce their reproductive success.
Samples collected from the Sacramento and
Feather rivers and their tributaries by the
U.S. Geological Survey (USGS) in 1992 showed that
diazinon levels exceeded the California Department
of Fish and Game's Hazard Assessment Criteria of
0.16 jUg/L 1-hour average (acute), O.IO/ug/L 4-day
average (chronic).
A 1993 study linked diazinon use on orchards
during the dormant season (December through
February) with elevated ambient concentrations
of diazinon and aquatic toxicity in the Sacramento
Figure 1.
Map showing
locations of
Sacramento
and Feather
rivers
and their
tributaries,
Sutter
Bypass and
Sacramento
Slough.
Figure 2.
Sacramento
Slough at
low-flow
conditions.
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and San Joaquin rivers. As a result of the USGS
sampling results, in 1994 the CV-RWQCB added a
16-mile segment of Sacramento River, from Knights
Landing to the Delta; a 42-mile segment of Feather
River from Lake Oroville to Sacramento River; and
the tributaries Sacramento Slough (1.7 miles) and
Sutter Bypass (19 miles) to the CWA section 303(d)
list due to aquatic toxicity caused by diazinon.
Over the next decade, state and federal resources
supported an extensive stakeholder process to
develop a total maximum daily load (TMDL) for
diazinon in the Sacramento River and Feather River
watersheds.
Results
Project Highlights
In 2001 the SRWP OP Pesticide Focus Group
completed its Water Quality Management Strategy
(Strategy) for diazinon in the Sacramento and
Feather rivers. The Strategy summarized two years
of research on the OP pesticide issue and presented
an implementation plan designed to reduce diazinon
in runoff during the dormant season. An Agricultural
Implementation Group composed of commodity
boards, pesticide registrants, and farm organizations
worked to implement the Strategy and install various
structural and management BMPs. For example,
landowners replaced flood irrigation in orchards
with piped sprinkler systems, installed filter strips,
planted cover crops, and transitioned to pest man-
agement practices that limit diazinon use.
The Central Valley Water Board's 2003 adoption and
subsequent implementation of the diazinon TMDL
water quality objectives and allocated reductions
was instrumental to the success of this project.
The development of the TMDL played a key role in
motivating the agricultural community to implement
BMPs.
In 2003 CV-RWQCB began using its authority
to regulate diazinon as a waste discharge from
irrigated lands. Also in 2003 the U.S. Environmental
Protection Agency (EPA) and pesticide manufactur-
ers developed local label restrictions for agricultural
uses of diazinon, including dormant-season applica-
tions. In 2004 the EPA Pesticide Program, under the
Federal Insecticide, Fungicide, and Rodenticide Act,
cancelled the registration and sale of diazinon pes-
ticides for indoor use, non-agricultural outdoor use
(lawns and gardens), and certain agricultural uses.
In 2006 the California Department of Pesticide
Regulation adopted diazinon dormant spray regula-
tions for agricultural applications. The regulations
prohibit the application of diazinon within 48 hours
of a forecasted storm or when soils at the applica-
tion site are saturated.
Implementing the diazinon TMDL and SRWP
Strategy to reduce diazinon runoff reduced diazinon
levels in all four waterbody segments. For example,
of 88 samples collected between 1996 and 2001
from the Sutter Bypass and 109 samples collected
between 2000 and 2005 from the Sacramento
Slough, none exceeded the water quality objec-
tive of 0.16 jUg/L 1-hour average. As a result, the
CV-RWQCB removed Sacramento Slough and
Sutter Bypass from the 2006 CWA section 303(d)
list for diazinon impairments. Samples collected on
the Sacramento River (193 samples between 2005
and 2007) and the Feather River (15 samples in
2004) also did not exceed the water quality objec-
tive for diazinon. Based on these data, CV-RWQCB
proposes to remove the 16-mile segment of the
Sacramento River and the 42-mile segment of the
Feather River from the 2010 CWA section 303(d) list
for diazinon impairments.
Polluted runoff from both agricultural and urban
areas continues to affect the water quality of the
Sacramento and Feather rivers. The SWRCB and
CV-RWQCB provide funding and technical assis-
tance to support collaborative efforts to address
continued aquatic toxicity problems.
Partners and Funding
Since 1991, EPA has awarded $7.6 million in special
appropriation funds to develop the SRWP. Another
$2.72 million in CWA section 319 grants sup-
ported several projects addressing diazinon in the
Sacramento and Feather River watersheds since
1997, including a $219,000 grant awarded in 1997 to
support ongoing SRWP planning and outreach/edu-
cation efforts, a $350,000 grant awarded in 2001 to
the California Dried Plum Board for implementing
the SRWP Strategy, and a $990,000 grant awarded
in 2005 to the Community Alliance with Family
Farmers for educating growers in Sutter and Yuba
counties and demonstrating mitigation measures
for dormant season spray application.
Other funding sources included a CALFED (a
state and federal consortium) Watershed Program
grant for $310,000 in 2002 and a $932,680 state-
bond-funded grant to the Coalition for Urban/Rural
Environmental Stewardship in 2002 for projects
that provided education, outreach and technical
assistance to orchard growers and Agricultural
Commissioners. In 2008 the Sutter County
Resource Conservation District received a USDA
Water Enhancement Program grant for $905,000 to
implement BMPs to reduce diazinon levels in runoff
to the Feather River.
PRO!
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-10-001EE
September 2010
For additional information contact:
Holly Grover
Central Valley Regional Water Quality Control Board
916-464-4747 • hgrover@waterboards.ca.gov
Daniel McClure
Central Valley Regional Water Quality Control Board
916-464-4751 • dmcclure@waterboards.ca.gov
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