Water Quality
Progress
Report
Lower Sacramento
and Feather Rivers -
Diazinon and
Chlorpyrifos
(Approved	2004,
WATER QUALITY
 TMDL targets achieved
o Conditions improving
o Improvement needed
o Data inconclusive
Contacts
EPA:
Erin Foresman at (916) 930-3722 or
foresman.erin@epa.gov
Central Valley Water Board:
Danny McClure at (916) 464-4751 or
dmcclure@waterboards.ca.gov
Last Updated 6/15/2015
Total Maximum Daily Load (TMDL) Summary
Waterbody - The middle and lower segments of the Sacramento River,
which flows from Lake Shasta to the Sacramento-San Joaquin Delta, and
the Feather River below Lake Oroville were impaired for diazinon and
chlorpyrifos; therefore a TMDL was developed. These water bodies are
located in the Sacramento Valley (see map) and drain approximately
5,200 square miles, which is the northern third of the California Central
Valley. The Sacramento River is the largest River in California and the
main source of freshwater flow to the Sacramento-San Joaquin Delta.
The Feather River is the largest tributary to the Sacramento River.
Shasta
Lake
* Red Bluff
.Chicc
f
Butts
Slough A),
Colusa
Sacramento
Colusa
Drain
Feather River
Butte/Sutter Basin
Natomas Basin/
American River
Natomas Cross Canal
Sacramento River
Above Colusa
Area of
Enlargement
Diazinon and Chlorpyrifos TMDL Area (Sacramento Valley Floor)
Water Quality Goals
To protect the freshwater habitat beneficial use, the TMDL includes
numeric water quality objectives (represented by concentrations in
micrograms per liter |ug/L|) that are not to be exceeded more than
once in a three year period:
Chlorpyrifos Acute	0.025 |ag/L (1 hour average)
Chronic	0.015 jag/L (4 day average)
Diazinon	Acute	0.16 jXg/L (1 hour average)
Chronic	0.10 jxg/L (4 day average)

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Progress Report: Diazinon and Chlorpyrifos in the Lower Sacramento and Feather Rivers
Targeted Attainment Date -Compliance with water quality objectives, waste load allocations, and load
allocations in the Sacramento and Feather rivers is required by August 11, 2008, which is the United States
Environmental Protection Agency (USEPA) approval date.
Water Quality Impairment -Diazinon and chlorpyrifos are two insecticides used in agricultural settings. These
insecticides can be acutely toxic to aquatic life, wildlife, and humans. Aquatic invertebrates appear to be the
aquatic organisms most sensitive to diazinon and chlorpyrifos exposure. These insecticides are also more toxic
when they are together in solution.
State and federal agencies, along with other groups, have been collecting samples in the Sacramento and Feather
rivers since the early 1990s. These monitoring data have confirmed the presence of diazinon and chlorpyrifos in
the Sacramento and Feather rivers and their tributaries. These waterbodies were first added to the California List
of Impaired Waterbodies in 1994 for aquatic toxicity caused by diazinon and chlorpyrifos, associated with
impairment of the freshwater habitat designated use. In addition, toxic substances, including pesticides, are
considered one of the stressors contributing to the collapse of the aquatic ecosystem in the San Francisco Bay
Delta Estuary, which gets most of its freshwater inflows from the Sacramento River.
Pollutant Sources - Diazinon and chlorpyrifos have historically been used in both urban and agricultural
environments. The product registrations for almost all non-agricultural uses of diazinon and chlorpyrifos were
cancelled by USEPA in 2004 and 2000, respectively. Because these pesticides are no longer sold for urban
residential use, their concentrations have decreased rapidly in municipal wastewater treatment plant and municipal
stormwater discharges. Agricultural applications are the primary sources of diazinon and chlorpyrifos to the
Sacramento and Feather rivers.
Pesticides applied to agricultural areas are transported to surface waters primarily by stormwater runoff and by
drainage or runoff of irrigation water. Agricultural pesticide application can be separated and evaluated by season.
Dormant season pesticide applications occur in the watershed during the winter months, generally from December
through February. During this season, pesticides are carried to surface water by stormwater runoff. Excess
pesticides on trees and the soil run off with the water during rain events. Irrigation season pesticide applications
occur from March through November. During the irrigation season, chlorpyrifos and diazinon move with
irrigation water from agricultural fields to the Sacramento and Feather rivers. In addition, throughout the year
localized drift from pesticide applications and atmospheric deposition can contribute pesticides to surface waters.
When diazinon and chlorpyrifos were first identified as causes of impairment to this watershed, most of the
diazinon application was occurring during the dormant season. During this dormant period, almonds, peaches, and
apricots accounted for most diazinon use. Almonds, cantaloupe, and peaches received the most diazinon during
the irrigation season. Chlorpyrifos had the opposite application trend as the majority was applied during the
irrigation season, particularly on almonds, cotton, alfalfa, and walnut. During the dormant season, almonds,
apples, and peaches were the primary crops sprayed with chlorpyrifos. Statewide, use of diazinon has decreased
between 2002 and 2012 in both agricultural and structural pest control, while use of chlorpyrifos has not changed
appreciably in that time.
Loading Capacity and Allocations - The loading capacity is the maximum amount of a contaminant or stressor
that can be assimilated in a waterbody without exceeding the TMDL numeric targets (which are equal to the water
quality objectives for this TMDL). The diazinon and chlorpyrifos loading capacity and source allocations in this
TMDL are concentration-based limits. These limits are measured in receiving waters. Additive toxicity was
incorporated into the loading capacity because diazinon and chlorpyrifos can be present at levels of concern at the
same time. They are more toxic to aquatic life when they are found in combination than they are individually. The
diazinon and chlorpyrifos loading capacity is represented by an equation, where the sum of diazinon and
chlorpyrifos concentrations divided by their corresponding water quality objective (i.e., the cumulative impact)
must be less than one (<1). This relationship is expressed as:
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Progress Report: Diazinon and Chlorpyrifos in the Lower Sacramento and Feather Rivers
Loading Capacity = (Cdiazinon/O diazinon) "I" (Cchlorpyrifos S/Ochlorpyrifos) ^ 1
Where:
Cdiazinon = Diazinon concentration in the receiving water.
Cchlorpyrifos = Chlorpyrifos concentration in the receiving water.
Odiazinon = Acute or chronic diazinon Water Quality Objective or criterion.
Ochlorpyrifos = Acute or chronic chlorpyrifos Water Quality Objective or criterion
Waste load allocations (point sources for municipal wastewater treatment plants and stormwater discharges with
National Pollutant Discharge Elimination System [NPDES] permits) and load allocations for agricultural nonpoint
sources are both set equal to the equation for the loading capacity. If each source and subwatershed does not
exceed one in this cumulative impact equation, then the loading capacity will be met.
Is Water Quality Improving?
The water quality has improved in the study area through successful efforts to reduce pesticide discharges
including the cancellation of non-agricultural uses and a substantial reduction in the use of diazinon and
chlorpyrifos as the agricultural sector transitioned to different pesticides, such as pyrethroids. Many other
activities were implemented before, during, and subsequent to the TMDL to reduce discharges of these pesticides
by reducing runoff through improved application practices, reduced use, and reduced runoff volume. Many
agencies and stakeholders have been involved in pesticide-control efforts including: growers, commodity groups
and pesticide applicators in the Sacramento Valley, California Department of Pesticide Regulation (DPR), County
Agricultural Commissioners, pesticide manufacturers, the University of California, the Sacramento River
Watershed Program, the Coalition for Urban and Rural Environmental Stewardship, and the Sacramento Valley
Water Quality Coalition (SVWQC).
Data collected in the Sacramento and Feather rivers indicate that these waterbodies are attaining the water quality
objectives for both chlorpyrifos and diazinon; therefore the TMDL loading Capacity and water quality objectives
are being achieved. The reduction of diazinon in the Sacramento and Feather rivers has been documented as a
nonpoint source success story by USEPA.
Overall, these results imply a positive change in water quality due to implemented management practices,
especially in the main stems. Continued monitoring and additional data are necessary to ensure that the diazinon
and chlorpyrifos concentrations remain below water quality objectives. In addition, additional sampling for
potential replacement pesticides is being conducted as required in the TMDL-related monitoring provisions. This
monitoring will be used to determine whether concentrations of alternative pesticides have increased as these
pesticides can also impact the health of aquatic organisms.
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Progress Report: Diazinon and Chlorpyrifos in the Lower Sacramento and Feather Rivers
Chlorpyrifos concentration trends in the Lower
Sacramento and Feather Rivers
0.1
c
o
'= 0.01
CO
0)
o
c
o
o
0.001
0.0001
~~
4 V
~ ~
0.00001
TMDL Approval and
Targeted Attainment
~ Sacramento
~ Feather
-Acute Objective
Chronic Objective
Diazinon concentration trends in the Lower
Sacramento and Feather Rivers
c
o
c

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Progress Report: Diazinon and Chlorpyrifos in the Lower Sacramento and Feather Rivers
Implementation Activity
Target Date
Status
Progress Details
Issue waiver of waste discharge
requirement (WDR), and WDRs
8/11/2008
Complete
	Water Quality Coalition waiver of WDR
issued in 2006 (link) as part of the
Central Valley Water Board's Irrigated
Lands Regulatory Program (ILRP).
	Updated in 2006, 2008, and 2011 (link).
	Third Party Group WDR issued in 2014
(link) for growers in the SVWQC.
Management Plans
None
specified
Complete
	Management Plans for the SVWQC are
approved annually, and include activities
to comply with this TMDL.
	Irrigated Lands Regulatory Program
(IRLP) is currently being implemented
(link).
Water Board review of the
allocations and implementation
previsions.
6/30/2013
Complete
Resolution R5-2014-0041 (link)
Water Board staff will meet at least
annually with staff from the
Department of Pesticide Regulation
and representatives from the
California Agricultural Commissioners
and Sealers Association to review
pesticide use and instream pesticide
concentrations during the dormant
spray and irrigation application
seasons, and to consider the
effectiveness of management
measures in meeting water quality
objectives and load allocations.
Annually
In Progress
	Coordination with County Agricultural
Commissioners is done by coalitions
under the ILRP.
	Meetings have occurred ancillary to
meetings to discuss other relevant and
timely topics.
Prohibition of Discharge
None
specified
Complete
	This has not gone into effect, since the
objectives and loading capacity are being
met.
	The Central Valley Water Board is,
however, following through with
enforcement for agricultural dischargers
without regulatory coverage under the
Irrigated Lands Regulatory Program
(ILRP).
Additional actions
None
specified
In
Progress
	In 2005, DPR, established regulations for
sprays of pesticides on dormant
orchards to reduce runoff. These are
enforced by DPR and the County
Agricultural Commissioners.
	Product registrations for most urban
(non-agricultural) uses of diazinon and
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Progress Report: Diazinon and Chlorpyrifos in the Lower Sacramento and Feather Rivers
Implementation Activity
Target Date
Status
Progress Details



chlorpyrifos were cancelled by USEPA in
2004 and 2000, respectively.
TMDL Monitoring Program Objectives
The SVWQC reports to the Water Board annually on monitoring required to meet the TMDL monitoring goals
under the ILRP. Progress on individual goals is summarized below.
1. Determine compliance with
established water quality objectives
(WQOs) and the loading capacity
applicable to diazinon and
chlorpyrifos in the Sacramento and
Feather Rivers.
None
specified
Complete
Data have been collected by the SVWQC
and others. These data indicate that
samples in the Sacramento and Feather
rivers are attaining the TMDL for both
diazinon and chlorpyrifos.
2. Determine compliance with
established load allocations for
diazinon and chlorpyrifos.
None
specified
Complete
Data indicate that samples in the
Sacramento and Feather rivers are
attaining the TMDL for both diazinon and
chlorpyrifos; therefore, the load allocations
have been met.
3. Determine the degree of
implementation of management
practices to reduce off-site
movement of diazinon and
chlorpyrifos.
None
specified
Complete/
Ongoing
Implementation of the approved
management plan is the primary
mechanism for addressing management of
diazinon and chlorpyrifos.
4. Determine the effectiveness of
management practices and strategies
to reduce off-site migration of
diazinon and chlorpyrifos.
None
specified
Complete/
Ongoing
Implementation of the approved
management plan is the primary
mechanism for addressing management of
diazinon and chlorpyrifos.
5. Determine whether alternatives to
diazinon and chlorpyrifos are causing
surface water quality impacts.
None
specified
Complete/
Ongoing
Both agricultural and stormwater
dischargers monitor for alternatives
insecticides which have potential to cause
impacts to water quality, as well as toxicity.
A number of pesticides of concern, such as
pyrethroids have been identified are being
addressed by the dischargers, the Central
Valley Water Board, DPR, and others
through various regulatory processes.
6. Determine whether the discharge
causes or contributes to a toxicity
impairment due to additive or
synergistic effects of multiple
pollutants.
None
specified
Complete/
Ongoing
Both agricultural and urban stormwater
dischargers are implementing toxicity
monitoring, which meets this goal.
Coalitions are required to conduct acute
toxicity monitoring in water and sediment
twice per year.
Some toxicity is present, however the
magnitude and extent of toxicity is much
less than the toxic pulses of diazinon which
were observed coming down the
Sacramento and Feather rivers and through
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Progress Report: Diazinon and Chlorpyrifos in the Lower Sacramento and Feather Rivers
Implementation Activity
Target Date
Status
Progress Details



the Delta in the early 1990s.
7. Demonstrate that management
practices are achieving the lowest
pesticide levels technically and
economically achievable.
None
specified
Complete/
Ongoing
To address specific water quality
exceedances, the Coalition and its partners
developed a Management Plan in 2008,
subsequently approved by the Water
Board. The Management Plan is updated
annually. Implementation of the approved
plan is the primary mechanism for
addressing exceedances observed in the
Coalition's ILRP monitoring.
What Next?
Water quality goals are currently being achieved. Application of both diazinon and chlorpyrifos has decreased as
many growers have begun using alternative pesticides, such as pyrethroids, which also cause aquatic toxicity.
Cancellation of residential uses of diazinon and chlorpyrifos has mitigated risks to aquatic life from these two
pesticides in urban areas but there are still risks from agricultural uses. Continued implementation of the ILRP
will be key to addressing these impairments. Likely new pesticides will emerge in the future and continued
monitoring for aquatic toxicity will be the most efficient way to assess pesticide impacts over time. During
pesticide registration and registration review, aquatic life risk mitigation strategies are developed into pesticide
use instructions that must appear on product labels and must be followed by pesticide applicators. Increased
coordination between State and Federal water quality and pesticide use regulators will help to achieve the long
term goal of improved aquatic health.
Information Source Documents
	TMDL Staff Report - May 2007 (report link; appendices link)
	Basin Plan Amendment (May 2007) - Amendment to the Water Quality Control Plan for the Sacramento River
and San Joaquin River Basins for the Control of Diazinon and Chlorpyrifos Runoff into the Sacramento and
Feather Rivers (link)
	Strategic Workplan for Activities in the San Francisco Bay/Sacramento-San Joaquin Delta Estuary (link)
	Irrigated Lands Regulatory Program (link) and Water Quality Monitoring (link)
	Monitoring and Reporting Program, Coalition Group Conditional Waiver of Waste Discharge
Requirements for Discharges from Irrigated Lands (link)
	Monitoring and Reporting Program, Order No. R5-2009-0875, for Sacramento Valley Water Quality
Coalition under Amended Order No. R5-2006-0053 Coalition Group Conditional Waiver of Waste
Discharge Requirements for Discharges from Irrigated Lands (link)
	Sacramento Valley Water Quality Coalition Annual Monitoring Reports/Plans and Water Board Staff
Review (2014, 2013, 2012, 2011, 2010, 2008, 2007, 2005) (link)
	Irrigated Lands Regulatory Program Water Quality Data available at California Environmental Data
Exchange Network (CEDEN link)
	EPA Reporting Watershed Improvement (SP12) Report, Improving California Central Valley Watersheds:
Diazinon Reduction in the Feather and Sacramento Rivers (link)
	EPA's Nonpoint Source Success Story (link)
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