Difference between revisions of "Total Maximum Daily Loads for Chlorpyrifos and Diazinon in Lower Salinas River Watershed in Monterey County, California"

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The year represents the year the water body was first listed for the given impairment.  Class 5 of the [http://www.swrcb.ca.gov/centralcoast/water_issues/programs/tmdl/303d/appendix_e.shtml | 303d] states that a TMDL is required but not.
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The year represents the year the water body was first listed for the given impairment.  Class 5 of the [http://www.swrcb.ca.gov/centralcoast/water_issues/programs/tmdl/303d/appendix_e.shtml | is a water body where the TMDL water quality standards are not met and a TMDL is required but not complete.
  
 
== Watershed Description ==
 
== Watershed Description ==

Revision as of 17:26, 12 April 2011

This page is a a summary of the Regional Water Quality Control Board Central Coast Region report on Total Maximum Daily Load for chlorpyrifos and diazinon for the Lower Salinas River Watershed, Monterey County, California (Rose et al. 2011)[1]. The summary was prepared by the Spring '11 ENVS 560/L Watershed Systems class at CSUMB.


Project Definition

In 2011, the Central Coast California Regional Water Quality Control Board (CCRWQCB), the State Water Resources Control Board and the Environmental Protection Agency (EPA) approved the Total Maximum Daily Load (TMDL) report for the pesticides, chlorpyrifos and diazinon for the Lower Salinas River Watershed in Monterey County, California. The TMDL report evaluated: current concentrations of both pesticides in the watershed area waterbodies, source identification, contaminant reduction, implementation actions, and monitoring requirements.

The water bodies of the Lower Salinas River Watershed are used for a variety of purposes including, but not limited to: groundwater recharge, wildlife habitat, industrial and agricultural supply, commercial and recreational fishing, and other recreational activities. When a water body fails to meet the minimum quality standards required for its beneficial uses (assigned purposes), a TMDL is established.

In 2001 the EPA reviewed the registration for both chlorpyrifos and diazinon[1]. The EPA mandated the restriction of both pesticides including the phase out and elimination of all residential and non-agricultural uses[2][3][4]. These restrictions were expected to facilitate concentration reductions in impaired waters of the Lower Salinas River Watershed. However, widespread agricultural use continues to contribute to the contamination of waterbodies.

The TMDL for Chlopyrifos and Diazinon addresses the following impaired waterbodies:

Water Body Chlorpyrifos Diazinon Unknown Toxicity Pesticides
Moss Landing Harbor 2008 5A 2008 5A 2008 5A 1990 5A
Old Salinas River Estuary 1990 5A
Old Salinas River 2008 5A 2008 5A 2008 5A
Salinas River Lagoon (North) 1992 5A
Tembladero Slough 2008 5A 2008 5A 2008 5A 1996 5A
Alisal Slough 2008 5A
Blanco Drain 2008 5A 2008 5A 1998 5A
Salinas Reclamation Canal 2008 5A 2008 5A 2008 5A 1992 5A
Salinas River 2008 5A 2008 5A 2008 5A 1994 5A
Espinosa Slough 2008 5A 2008 5A 1996 5A
Espinosa Lake 2008 5A 2008 5A
Natividad Creek 2008 5A
Quail Creek 2008 5A 2008 5A 2008 5A
Chualar Creek 2008 5A 2008 5A 2008 5A

The year represents the year the water body was first listed for the given impairment. Class 5 of the [http://www.swrcb.ca.gov/centralcoast/water_issues/programs/tmdl/303d/appendix_e.shtml | is a water body where the TMDL water quality standards are not met and a TMDL is required but not complete.

Watershed Description

The project area consists of the Salinas River valley floor north of Gonzalez, out to the dunes along the Monterey Bay. The TMDL study is defined by the lower 400 square miles (195,000 acres) of the Lower Salinas River Watershed and includes two major drainage ways leading to Moss Landing Harbor and Salinas River Lagoon (North).

Surface water sources include precipitation, releases from reservoirs, groundwater, and return flows from agricultural irrigation. Mean annual precipitation in the project area ranges from approximately 13 to 16 inches per year with the majority of precipitation occurring between November and April.

Land use in the project area includes intensive agriculture as well as the urban centers of Salinas, Castroville and Prunedale.

The project area is characterized by both ephemeral and perennial stream reaches, as the Lower Salinas River runs dry during the summer months, and in comparison the lower Reclamation Ditch flows year-round.

Problem Statement

Within the Lower Salinas River Watershed fifteen waterbodies are impaired as a result of pesticides (chlorpyrifos or diazinon) or unknown toxic contamination and only eleven are listed as impaired according to the Clean Water Act 303(d) list. All Beneficial uses (BUs) of the waterbodies impaired by high concentrations of chlorpyrifos and/or diazinon are shown in the table below where "P" denotes a BU directly affected by increased diazinon and chlorpyrifos, "X" denotes all other BUs of the waterbody, "E" denotes an existing BU, and "a" denotes a BU occurring in the North Harbor.

BUs for Inland Waters

Waterbody MUN AGR PROC IND GWR REC1 REC2 WILD COLD WARM MIGR SPWN BIOL RARE EST FRESH COMM SHELL
Old Salinas River Estuary X X P P P P P X P P X X
Salinas River Lagoon (North) X X P P P P P X P P X X
Tembladero Slough X X P P P P P X X
Espinosa Lake X X P P X
Espinosa Slough X X P P X
Salinas Reclamation Canal X X P P X
Alisal Creek X X X X X P P P P X
Blanco Drain X X P P X
Salinas River, dnstr of Spreckels Gage X X X P P P P X X
Salinas River, Spreckels Gage-Chualar X X X X X X X P P P P X

BUs for Natividad Creek, Quail Creek, Chualar Creek, Old Salinas River, and Alisal Slough are not specifically assigned. However, MUN and recreational and aquatic habitat uses are assigned to characterize the waterbodies.

Existing and Anticipated BUs for Coastal Waters

Coastal Water REC1 REC2 IND NAV MAR SHELL COMM RARE WILD
Moss Landing Harbor E E E E E Ea E E E

E represents an existing BU and a is representative of a BU occurring in the North Harbor.

Data Analysis & Sources

Water quality data for Diazinon and Chlorpyrifos were collected under protocols specified by the California Dept of Fish and Game (CDFG)[1]. Although the CDFG protocol for Criterion Maximum Concentrations (CMC) called for hourly averaged data, instantaneously collected samples were treated as one hour average samples due to data collection limitations. Additionally, the CDFG published criterion for continuous concentrations (CCC), where a four day average would be collected. Water quality data collection staff have so far not been able to collect four day average samples, and therefore an assessment on chronic toxicology is not currently available. As stated in the 2011 report, staff will incorporate a four day average sampling frequency during the TMDL implementation.

The following documents and data were used by water board staff to produce the TMDLs for Chlorpyrifos and Diazinon in the Lower Salinas River watershed [1] :


In general, these studies observed that while some water bodies have Chlorpyrifos and Diazinon concentrations within acceptable ranges, the majority of sampled sites had concentrations exceeding regulated thresholds. Additionally, the studies found that toxic concentrations of Chlorpyrifos and Diazinon exist year round, with increased concentration during the drier summer months.

Numeric Target

Numeric targets were established for Chlorpyrifos and Diazinon to facilitate the designated beneficial uses described in Basin Plan. In the impaired waterbodies of the Lower Salinas watershed, the numeric targets of Chlorpyrifos and Diazinon were created to uphold Aquatic Life and defined by a 2000 report by the CDFG. The goal is for all water bodies covered in the TMDL to meet the numeric targets for the water column, including additive numeric targets which include the presence of both organophosphate pesticides.

Water Column Numeric Targets

The criterion maximum concentration (CMC) is the average concentration per 1-hour period. The criterion continuous concentration (CCC) is the 4-day concentration average. Both the CMC and the CCC are not to be exceeded more than once over the course of any 3-year period. The table below contains the CMC and the CCC for water column numeric targets for each pesticide:[1][5].

Compound CMC (ppb) CCC (ppb)
Chlorpyrifos 0.025 0.015
Diazinon 0.16 0.10

Additive Toxicity Numeric Targets

The additive numeric target is applicable when both chlorpyrifos and diazinon are present in the water column. This additive target is calculated as follows:

<math> {Cdiazinon \over NTdiazinon} + {Cchlorpyrifos \over NTchlorpyrifos} = S ; S\le1.0 </math>

Where:

C= concentration of pesticide measured in water body.
NT= the numeric target for the water body.
S = sum. If the sum is greater than 1.0, the water is impaired and the beneficial uses are effected.

Source Analysis

The CCRWQCB examined data regarding use of both chlorpyrifos and diazinon in the lower Salinas River watershed and concluded that agricultural lands were the primary source for both chlorpyrifos and diazinon[1].

Linkage Analysis

Linkage Analysis is intended to link the numeric target concentration (amount per volume) to a daily load (amount per day) for the watershed. For Chlorpyrifos and Diazinon the load allocations are specified in terms of concentration (amount per volume) and thus are equal to the numeric targets. These are the same values that are used for the TMDL.

TMDL Development

The TMDL for Chlorpyrifos and Diazinon are expressed as concentrations. The TMDL's for the region are equal to the CMC numeric targets (0.025ppb for chlorpyrifos and 0.16ppb for diazinon), CCC numeric targets (0.015ppb for chlorpyrifos and 0.10ppb for diazinon), and the additive numeric targets. For each 303d listed water body water body the CCRWQB utilizes the concentrations set by the CDFG. The TMDL requires that discharges into impaired water bodies meet the established concentrations.

Margin of Safety

The Margin of Safety (MOS), a component of the TMDL, accounts for uncertainty concerning the relationship between pollutant and waterbody quality (http://www.epa.gov/reg3wapd/tmdl/glossary.htm). TMDLs for chlorpyrifos and diazinon were adopted from numeric limits developed by the California Department of Fish and Game (CDFG), using protocols created by the United States Environmental Protection Agency (USEPA). The MOS for chlorpyrifos and diazinon are implied in the numeric targets made in the TMDL. These TMDLs assume there are no additional reductions in compounds resulting from degradation or sediment deposition. Since it is likely that these processes will take place, this assumption adds to the margin of safety.

The MOS for chlorpyrifos and diazinon are:

Compound CMC (ppb) CCC (ppb)
Chlorpyrifos 0.025 0.015
Diazinon 0.16 0.10

Where: (CMC) is the average concentration per 1-hour period and(CCC) is the 4-day concentration average

Critical Conditions and Seasonal Variation

Critical conditions are defined as environmental factors that result in exceedance of the water quality standard expressed in terms of load. Because this TMDL is expressed as a concentration, which is equal to the desired water quality condition, there are no critical conditions reported. An exceedance of the criteria for water quality is possible regardless of season and therefor not specified in the TMDL for Chlorpyrifos and Diazinon.

TMDL Allocations

In TMDL documents, a polluter's discharge is limited by 'Wasteload' (WLA, non-point sources) and 'Load Allocations' (LA, point sources) that represent the maximum load of a pollutant that each discharger is allowed to release. In the Chlorpyrifos and Diazinon TMDLs for the Lower Salinas River Watershed allocations and maximum loads are concentration-based and apply to owners and operators of irrigated agricultural lands who have discharges from their lands. Since this TMDL is concentration-based the LA and WLA are allotted the same concentration which are given in the #Numeric Target section above.

Public Participation

In an effort to include the public in the development of TMDLs, the Central Coast Water Board (CCWB) solicited public participation in a 45-day public comment period preceding the Central Coast Water Board hearing. Public notice of the hearing was mailed to interested persons and to applicable government agencies, and were available on CCWB website. A series of meetings were conducted to form the current final report for the the Chlorpyrifos and Diazinon TMDL and included the following stakeholders:

A series of stakeholder meetings were conducted to form the current final TMDL report with stakeholder input[6].

Implementation and Monitoring

The Chlorpyrifos and Diazinon TMDLs will be implemented through the Conditional waiver of waste discharge requirements for irrigated lands(Ag Waiver), and the California Department of Pesticide Regulation (DPR). Suggestions for implementation, monitoring, and tracking TMDL progress is given in The Total Maximum Daily Loads for Chlorpyrifos and Diazinon in Lower Salinas River Watershed in Monterey County, California: Final Project Report (Final Project Report) [1].

Implementation

Ag Waiver

The TMDLs for chlorpyrifos and diazinon will be implemented through the Ag Wavier. Within two years following the adoption of the March 2011 draft Ag Waiver, participating growers which are discharging chlorpyrifos and diazinon into watereways are required to demonstrate that they are not contributing to exceedences in numeric targets. CCRWQCBs allocations, numeric targets, and TMDLs in the impaired waterbodies are planned to be achieved by 2025. However, accelerated implementation is preferred by CCRWQCB whenever feasible in order to reach targets as soon as possible. The Ag Waiver is the regulatory tool used by the water board to enforce and evaluate the implementation of this TMDL. The Ag Waiver is seen by the CCRWQCB as a sufficient regulatory mechanism to remedy impairments caused by chlorpyrifos and diazinon.

The Final Project Report recommends the draft Ag Waiver establish timeframes for individual dischargers to reach set water quality standards, giving the shortest timeframes to dischargers who pose the greatest risk to water quality. The Ag Waiver states that if a contaminant discharger does not meet the deadlines provided in the March 2011 draft Ag waiver (link), enforcement actions may be made by the CCRWQCB. Compliance with TMDL requirements is assessed by CCRWQCB, through inspections and monitoring. Chlorpyrifos and diazinon numeric target exceedences will be reevaluated CCRWQCB staff when monitoring data is received and during future renewals of the Ag Waiver. The conditions of future Ag Waivers will then be modified to address remaining sources of surface water impairments. The Waiver states that if the discharger does not meet deadlines, enforcement actions will be made by the CCRWQCB.


California Department of Pesticide Regulations

In addition to the Ag Waiver, the California Department of Pesticide Regulations (DPR) is another regulatory mechanism that may reduce the amount of chlopyrifos and diazinon entering waterways. DPR is required to reevaluate registration of pesticides. If adverse effects to surface waters caused by chlorpyrifos and diazinon cannot be mitigated, DPR can cancel or suspend the registration of the pesticides


TMDL Final Project Report Recommendations

Other than placing growers using diazinon or chlorpyrifos into Tier 3 monitoring strategy outlined by the 2011 draft Ag waiver (the most stringent monitoring Tier), there are no specific implementation requirements for these two pesticides. However, The Final Project Report, provides the following suggestions for implementation:

  • hold agricultural runoff for 72 hours after pesticides are applied
  • improve granular application methods to prevent spills
  • use enzymes to degrade the chemicals before they enter waterways
  • incorporate drip irrigation to reduce agricultural runoff
  • rotate crops which do not harbor pests requiring pesticides

Monitoring

The TMDLs for chlorpyrifos and diazinon are implemented, monitored, and enforced through the Ag Waiver. The March 2011 draft Ag Waiver proposes to require growers to either perform individual water quality monitoring (Tier 3) or participate in cooperative water quality monitoring (Tier 2 & 1) (e.g. The Cooperative Monitoring Program managed by Central Coast Water Quality Preservation Inc. ). Land owners must also complete annual implementation and management progress reports RWQCB. To reach objectives of CCRWQCB, new monitoring and reporting strategies are included in the March 2011 draft Ag Waiver, to assess progress towards reaching Cholpyrifos and Diazinon TMDL limits. (ref -Final report)


March 2011 Draft Ag Waiver Monitoring Requirements The March 2011 draft Ag Waiver has now split monitoring into three Tiers of monitoring requirements. All growers who discharge chlorpyrifos or diazinon into waterways automatically fall under Tier 3 monitoring requirements, the highest degree of monitoring required by the Ag Waiver. The 3rd tier of Ag Waiver monitoring requires each qualifying individual grower to individually:

  • conduct monthly water quality sampling following Ag waiver sampling protocols
  • conduct photo-monitoring documenting waterway condition
  • create a Water Quality Buffer Plan
  • produce quarterly discharge monitoring reports


TMDL Final Project Report Recommended Monitoring Strategy

The following recommendations have been made by Cal EPA and Region 3 RWQCB for monitoring and reporting strategy in the next Ag Waiver. Monitoring and reporting for Chlorpyrifos and Diazinon should (reference):

  • Span a variety of flow regimes, with sampling occuring four times per water year; twice between May 15th and October 15th, and twice between Oct 15th and March 15, aproximately. One of these sampling events between October 15 and March 15th should include a 7-day continuous sampling event during and/or following a storm event.
  • Encourage high-resolution source analysis near farming operations using chlorpyrifos or diazinon that discharge to waterbodies impaired by chlorpyrifos, or diazinon, or toxicity
  • Use laboratory and analytical methods that enable data comparison with numeric targets
  • Include toxicity identification evaluation (TIE) for waterbodies listed as impaired for toxicity, or unknown toxicity. Implementing suggested monitoring and reporting requirements if TIEs help determine chlorpyrifos or diazinon are contributing to toxicity in a waterbody.
  • Be located in the lower portions of the watershed, whenever feasible, giving preference to previously established monitoring sites to facilitate trend detection.


Proposed Impaired Waterbody Monitoring Sites

Impaired Waterbody Proposed Monitoring Site
Tembladero Slough 309TEH
Alisal Slough 309SSB
Blanco Drain 309BLA
Salinas Reclamation Canal (Upper) 309ALG
Salinas Reclamation Canal (Lower) 309JON
Salinas River 309SSP
Espinosa Slough EPL-EPL
Espinosa Lake EPL-EPL
Natividad Creek 309NAD
Quail Creek 309QUA
Chular Creek 309CRR

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Rose C, Harlan L, Osmolovsky P. 2011. Regional Water Quality Control Board Central Coast Region. Available from:Total Maximum Daily Loads for Chlorpyrifos and Diazinon in Lower Salinas River Watershed in Monterey County, California
  2. USEPA. 2011. Diazinon:Phase out of all residential uses [Internet]Available from: http://www.epa.gov/pesticides/factsheets/chemicals/diazinon-factsheet.htm
  3. USEPA. 2005. Pesticide News Story: Chlorpyrifos Pre-Construction Termiticide Products Phase Out on December 31, 2005.[Internet].Available from: http://www.epa.gov/oppfead1/cb/csb_page/updates/chlorpy-phasout.htm
  4. DPR. 2003. Diazinon and Chlorpyrifos Loads in Precipitation and Urban and Agricultural Storm Runoff during January and February 2001 in the San Joaquin River Basin, California http://www.cdpr.ca.gov/docs/emon/surfwtr/contracts/USGS_03-4091.pdf
  5. Siepmann S, Finlayson B. 2000. California Department of Fish and Game. Available from:Water Quality Criteria for Diazinon and Chlorpyrifos
  6. Resolution (No. R3-2011-0005). 2011. Regional Water Quality Control Board Central Coast Region. Available from:Resolution (No. R3-2011-0005)

Links

Disclaimer

This page may contain student work completed as part of assigned coursework. It may not be accurate. It does not necessary reflect the opinion or policy of CSUMB, its staff, or students.