TMDL for Fecal Coliform for the Lower Salinas River Watershed, Monterey County, California

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This page is a a summary of the Regional Water Quality Control Board Central Coast Region report on Total Maximum Daily Load for Fecal Coliform for the Lower Salinas River Watershed, Monterey County, California (CCRWQCB, 2009)[1]. The summary was prepared by the Spring '10 ENVS 560/L Watershed Systems class at CSUMB.

Project Definition

The California Regional Water Quality Control Board for the Central Coast Region (CCRWQCB), in collaboration with the Environmental Protection Agency (EPA), established a Total Maximum Daily Load (TMDL) for Fecal Coliform for the Lower Salinas River Watershed in Monterey County, California. The final report was available as of September 2, 2010.

The TMDL report addresses the impairment due to fecal contamination of the Lower Salinas River and several of its tributaries by examining increased fecal coliform concentrations. The fecal coliform group of bacteria are readily used as indicator species [fecal indicator bacteria (FIB)] for fecal pathogens in water bodies. If fecal coliform concentrations exceed certain criteria, the water body may be listed as impaired pursuant to Section 303(d) of the Clean Water Act. The project area includes the following impaired water bodies:

Water Body Listed for Fecal Coliform
Alisal Creek 2002 5A
Chualar Creek 2008 5A
Gabilan Creek 2002 5A
Lower Salinas River 2002 5A
Old Salinas River 2008 5A
Quail Creek 2008 5A
Salinas Reclamation Canal 2002 5A
Salinas River 2008 5A
Santa Rita Creek 2008 5A
Tembladero Slough 2008 5A

The water bodies of the Lower Salinas 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.

Problem Statement

The Lower Salinas River and eleven of its tributary waterbodies are impaired under section 303(d) of the Clean Water Act due to elevated levels of fecal coliform. Observed levels of fecal coliform do not meet the water quality objectives for some of the Beneficial uses (BUs) of the listed waterbodies. In the table below an "X" denotes a BU and "FC" denotes a BU impaired due to fecal coliform.

Salinas River, Spreckels Gage- Chualar X X X X X FC FC X X X X X
Salinas River, dnstr of Spreckels Gage X X FC X X X X X X
Salinas River Lagoon (North) FC FC X X X X X X X X X FC
Old Salinas River Estuary FC FC X X X X X X X X X FC
Tembladero Slough FC FC X X X X X X FC
Salinas Reclamation Ditch FC FC X X X
Gabilan Creek X X X FC FC X X X X
Alisal Creek X X X FC FC X X X X X

Current Status

This TMDL was approved by the Regional Water Quality Control Board on September 2nd, 2010 and is awaiting State Water Resource Control Board approval (as of April 12, 2011). Up to date status for this TMDL is available from the Central Coast Regional Water Quality Control Board TMDL Status Page.

Data Analysis

The Salinas watershed was found to be impaired due to elevated concentrations of Fecal Indicator Bacteria (FIB). FIB indicate the general presence of fecal coliform and Escherichia coli O157:H7, and are monitored because specific human pathogens are difficult and expensive to measure. There is some scientific uncertainty about the accuracy of FIB as a gauge for pathogen risk, but monitoring FIB is currently the most cost efficient and effective method.

The presence of FIB were determined through water sample analysis using various methodologies including The Multiple Tube Fermentation (MTF) method and the Colilert method, the polymerase chain reaction (PCR), culture, and Pathatrix methods. The combination of these various methods indicated the magnitude of the pathogen problem and the potential presence of other fecal pathogens. Analysis of the results from these various methods, indicated the presence of a pathogen problem, consistent with the listing of the The Lower Salinas Watershed as "impaired."

Spatial data were used to estimate the impact of various land uses on waterbodies. Spatial data analyzed included streams, watershed boundaries, roads, land use and elevation. FIB concentration and presence data were also analyzed temporally, with respect to the dry and wet seasons. USGS flow data were incorporated into the study to estimate current load and assimilative capacity, and to derive daily load expressions.

E. coli rain event data were collected from thirteen sites after two separate rain events, neither of which were first flush rain events. It was found that the median E.coli density was significantly higher during rain events (2,685 MPN/100mL) than non rain events (224 MPN/100mL). There were multiple identifications of E. coli O157:H7, mostly at the confluence of Gabilan Creek and Towne Creek in the northern part of the study area. E. coli O157:H7 identification coincided with pasture and shrubland areas with generally large amounts of ranch land and animal activity.

Other assessed waterbodies for which data did not indicate impairment, or for which data were insufficient were:

  • Blanco Drain- not impaired
  • El Toro Creek- insufficient data
  • Alisal Slough- insufficient data

Numeric Target

Numeric targets for FIB are established in the Basin Plan based on the designated beneficial uses of a given water body. In the impaired waterbodies of the Lower Salinas watershed, the numeric targets of FIB for Water Contact Recreation, Non-Contact Recreation, and Shellfish Harvesting were noted as being exceeded. As shellfish harvesting is likely to be eliminated as a beneficial use, the numeric target adopted by the TMDL is the water quality standard for Water Contact Recreation (which is the next most protective beneficial use).

The goal is for all water bodies in the TMDL area to meet this numeric target:

  • The total coliform concentration for a minimum of five samples in any 30 day period should not exceed a log mean (i.e. geometric mean) of 200 per 100 ml, or 400 per 100 ml for 10% of total samples in any 30 day period.

Linkage Analysis

In a TMDL document, the Linkage Analysis is intended to link the numeric target concentration (amount per volume) to a daily load (amount per day) for the watershed. No explicit linkage analysis was given in the TMDL report because the CCRWQCB expressed the intent to implement the TMDL based on a target concentration of fecal coliform rather than a load. However, under the 'TMDL Development' section of the TMDL report, methods are described to link target concentrations to loading capacity.

TMDL Development

The official TMDL objective is expressed as a numeric target concentration that applies to all impaired waterbodies in the lower Salinas River watershed. In the TMDL report, the target concentration is also converted to maximum allowable loads (MPN/per day) for each individual waterbody as mandated by Friends of the Earth, Inc. v. EPA, et al..

The maximum allowable loads for fecal coliform are based on a three-tiered flow regime, wherein each water body has different allowable loads established for high (top 5%), moderate (middle 25%), and low (bottom 60%) flows. For ungaged streams, flow was estimated from measurements on comparable streams and adjusted based on the Drainage Area Ratio (DAR). Allowable loads were calculated by multiplying the average flow within each flow regime (low, moderate, or high) by the target concentration [volume/time * mass/volume = mass/time] and then compared to existing loads derived from field data.

For example, at Gabilan Creek, during an average high flow event of 26 cfs, the Total Maximum Daily Load of FIB that can be absorbed without exceeding the target concentration is <math> 2.8 \times 10^{11} </math> (orgs/day). This goal represents an 89% reduction from the current estimated load of <math>2.62 \times 10^{12}</math> (orgs/day).

Margin of Safety

TMDLs are required to include a margin of safety that accounts for uncertainty in the linkage between loading capacity of the watershed and pollutant concentration in the receiving water body. In the case of fecal coliform, the goal specified in the TMDL report is for all controllable water sources to meet the target concentration. As a load-based approach was not adopted in the TMDL, no margin of safety was given.

Critical Conditions and Seasonal Variation

The TMDL report does not identify any "critical" environmental factors, in which a slight change could lead to exceedence of water quality objectives. However, it was noted that pollutant concentration is dependent on flow volume, which is often irregular in Monterey County. Also, localized areas of stagnant water with fine sediments foster bacterial growth and may increase concentrations of Fecal Indicator Bacteria.

TMDL Allocations

In TMDL documents, 'Wasteload' and 'Load Allocations' are the maximum load of a pollutant that each point-source discharger is allowed to release. In the TMDL report summarized here, they are equal to the TMDLs (which are actually concentrations; see above), and are thus expressed as receiving water concentrations. For non-human fecal indicator bacteria, allocations are the numeric target for fecal coliform and equal to the concentration-based TMDL. The allocation assigned for human FIB is zero because of the increased pathogenic risk related to human waste.

Wasteload and load allocations for responsible parties associated as sources of fecal coliform for waterbodies are shown in Table 10-1 of the TMDL report.

Public Participation

There are many stakeholders in the Lower Salinas Watershed who would be affected by the implementation of the fecal coliform TMDL. These stakeholders represent:

  • Agriculture
  • Industry
  • Sewer discharge facilities
  • Wildlife
  • Fisheries
  • Sporting recreational activities
  • Municipal and domestic water supply
  • Homeless Persons

CCRWQCB incorporated stakeholder outreach efforts throughout the development of the TMDL. Data collection and analysis were organized in collaboration with county, state and federal agencies. Public presentations were readily conducted to inform and elicit stakeholder opinion from a variety of public and private institutions. All the results were made public.

Stakeholders had the opportunity to participate in public meetings where they could ask questions and voice their concerns. One of the concerns described was that specific waterbodies in the project area could not achieve the numeric targets required for coliform bacteria. The stakeholders added that some waterbodies are on private land, and therefore have other uses besides recreational use. Water flow on these lands is not always natural, especially during summer months when irrigation and groundwater pumping is used. Increased concentrations of the fecal indicator bacteria in these waterbodies may result from evaporation, and so the required numeric water quality objectives may be exceeded. The CCRWQCB is presently responsible for addressing these types of concerns and comments, and for providing official responses before the TMDL listing is approved.

Implementation and Monitoring

Implementation of the TMDL will occur by reducing pathogen loads from point and non-point sources, using a variety of existing and proposed regulatory mechanisms such as stormwater permits & storm water management plans, NPDES permits, waste discharge requirements, and waste discharge prohibitions. Key pollutants will be identified and the responsible parties will submit reports to the CCRWQCB outlining the results. Point sources of fecal coliform were identified as storm drain discharges to storm sewer systems and spills and leaks from sanitary sewer collection and treatment systems. Nonpoint sources include domestic animal discharges in areas that do not drain to a storm water sewer system, onsite waste disposal systems, illegal dumping, homeless encampments, sediment sources, runoff from irrigated agriculture, and non-controllable natural sources (wind-borne debris). Responsible parties include the City of Salinas, the County of Monterey, Salinas Industrial WWTP, the Castroville Water District, the County of Monterey Regional group, and owners and operators of lands with domestic animals, lands used for illegal dumping and lands with homeless encampments. The CCRWQCB is responsible for estimating and reporting how much implementation and monitoring costs.


  • Implementation Actions: Mandatory municipal storm water permits require all those who discharge to municipal storm sewage systems to implement a Storm Water Management Plan that includes an effectiveness assessment strategy. Compliance with the Domestic Animal Waste Discharge Prohibition is required for all owners and/or operators of property that have livestock, farm animals and pets. Anyone who has homeless people camping on their property is required to comply with the Human Fecal Material Discharge Prohibition. The County of Monterey and city officials prosecute incidents of illegal dumping. Complaints are investigated and financial rewards are given to anyone who helps identify offenders. Education and outreach programs are in place to help stop illegal dumping.
  • Evaluation of Implementation Progress: Implementation progress will be evaluated and reviewed every three years according to water quality improvements and attainment of trackable implementation actions. After reviewing all reports, programs and evaluations, the CCRWQCB will decide which actions need to be taken to achieve the TMDL numeric targets. Numeric targets must be achieved 13 years after the Office of Administrative Law approves the Fecal Coliform TMDL for the lower Salinas River basin. Additional non-point source polluters may be identified and additional provisions may be necessary if numeric targets are not achieved within the estimated time frame.


  • Monitoring Sites: Fecal Coliform testing must be performed in receiving waters and urban storm water outfall discharges. Fourteen water bodies have been proposed for monitoring locations. These include: Salinas River, Reclamation Canal, Salinas River Lagoon (North), Old Salinas River, Alisal Creek, Gavilan Creek (3 sites), Towne Creek, Natividad Creek, Santa Rita Creek, Tembladero Slough, Quail Creek and Chualar Creek. Five storm drain monitoring sites were selected. Receiving waters will be monitored with a minimum of five water quality samples within one 30 day period. One collection is done during the wet season(January 1 – March 31) and one during the dry season (May 1 – September 30). To identify the extent of fecal coliform concentrations from storm water drain discharges, samples will be collected in three storm events (between October 15 – April 30) and two dry season flows (between May 1 – October 14).


  1. Rose C, Osmolovsky P, Harlan L. 2010. Regional Water Qualtiy Control Board Central Coast Region. Available from:Total Maximum Daily Load for Fecal Coliform for the Lower Salinas River Watershed, Monterey County, California



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