TMDLs in the Monterey Bay Region of California

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This page summarizes the development and implementation of Total Maximum Daily Load (TMDL) plans in the Monterey Bay Region of California. The page was created by the ENVS 560/L Watershed Systems class at CSUMB.


Under 1987 provisions (section 304 (1)) to the Clean Water Act of 1972, states must identify and report all water bodies which do not meet water quality or beneficial use standards. Those impaired water bodies (i.e. polluted) not meeting water quality standards must be placed on the 303d list.

States must submit updated lists every two years. Along with identification of impaired water bodies, states must also identify stressors causing the impairment (i.e. pollutants), which are also identified on the 303d list. A remediation plan must then be developed and implemented for each impaired water body listed.

These plans are known as total mean daily loads (TMDLs). TMDLs are used to define and achieve a total maximum daily load for each pollutant causing impairment within their respective water body. The list also identifies where a TMDL has been approved by the Environmental Protection Agency (EPA) and implementation is available but water quality standards have not been met yet and where an action other than a TMDL is being used to address the issue.

Central Coast 303d list documents

The 303d list for the Central Coast Region of California is maintained by the Central Coast Regional Water Quality Control Board.

The following links present, explain, and discuss the 303d list for Central Coast Region of California:

Summary of listing categories. The CCRWQCB has assigned grouped 303d listings into the following categories[1]:

  • Category 1. All core uses are supported;
  • Category 2. At least one core use is supported;
  • Category 3. Insufficient information exists to make a determination;
  • Category 4A. At least one core use is not supported, however "a TMDL has been developed and approved by USEPA and is reasonably expected to result in the attainment of the water quality standard within a reasonable, specified time frame (p.10, CCRWQCB)."
  • Category 4B. At least one core use is not supported, however "an existing regulatory program is reasonably expected to result in the attainment of the water quality standard within a reasonable, specified timeframe (p.10,CCRWQCB)."
  • Category 5. At least one core use is not supported. A TMDL needs to be developed.

Monterey Bay area listings

The closest listings to Monterey Bay include: [2]


For more details, see:

Approaches to nutrient TMDL development are in the following reports:

  • The Chorro Creek Nutrient TMDL report set a sodium concentration limit of 50 mg/L and total dissolved solids concentration of 500 mg/L in order to help achieve the water quality objective for nutrient concentrations.
  • The Pajaro River and Llagas Creek report sets the maximum concentration for nitrate within the water body at 10mg/L in order to protect beneficial uses. The report does not include seasonality because it the TMDL is equal to the water quality objectives of the region.
  • The San Diego Creek and Newport Bay Report set the nitrate TMDL according to different seasons. They allow 13 lbs/day of inorganic nitrogen for reach 2,224 lbs/day from October 1 to March 31 total nitrogen and 175 lbs/day from April 1 to September 30.

TMDL development and implementation

The federal EPA provides protocols for TMDL development in general, and for specific types of constituents such as pathogens. These protocols outline the following components of a TMDL:

  • Identify waters requiring TMDLs
  • Priority ranking and targeting
  • Develop TMDLs (see below)
  • Assess control actions
    • Evaluating success of control actions through monitoring is required in some states, but this is not directly required at the federal level unless a point source permit under section 402 is revised[3].

Components of TMDL development

According to EPA Protocols[4], TMDLs should be comprised of the following components, which are typically described in separate sections of each TMDL Report:

  • Problem Statement
    • Identify Problem
      • Problem identification starts the process of the TMDL by summarizing the existing impairments, where they are located, and what probable sources are known. Collecting existing data, identifying designated uses, and evaluating seasonal factors are parts of this early summary.
  • Numeric Targets
    • Develop Numeric Targets
      • Research applicable water quality standards for the water body depending on jurisdictions and uses.
    • Select indicators
      • Technical and general scientific validity and practical time and cost considerations are useful in selecting which indicators to pick.
    • Identify target values
      • Choosing target values or conditions is complex, so local examples and experience in setting target values is extremely useful in the process. Historical pollutant levels (especially reference reach conditions) can help start the process. Other factors to consider when setting values are seasonal fluxes and spatial variability in the indicator. Values can be graduated on categorical type (e.g. tributary vs. main stem), and a margin of safety should be applied. The margin of safety is based on reliability and accuracy of indicator measurements, the degree of impairment, direct impacts, and best professional judgment based on experience and literature.
    • Compare existing and target conditions
  • Source Assessment
    • Identify sources
      • Inventory possible sources, characterize types of sources and their possible pathways.
    • Estimate source loadings
      • Monitoring data, statistical relationships, and models are used to estimate loads.
  • Linkage Analysis
    • Link Targets and Sources
      • Identify pathways of cause and effect between pollutant source and water quality target. Define needed level of analysis and then use monitoring data, variability, hydraulic characteristics, and type of indicator to create links. Simulation models can be utilized when other means are not sufficient to link indicators and sources.
    • Assess linkages
    • Estimate total loading capacity
  • Allocations
    • Load allocation
    • Divide load among sources
  • Monitoring/Evaluation Plan
    • Develop monitoring plan
    • Develop review plan
    • Develop schedule
    • Implementation Plan
    • Develop plan
      • Currently, once a TMDL is developed and approved for a water body it can be removed from the 303d list[3]
  • Implement control action
    • This can involve lowering permitted discharges if present, and using as many other strategies as possible. Other strategies could be regulations, educational programs, best management practices, cost-sharing or other assistance, and use of volunteer groups[3].

Approaches to TMDL development and implementation in the Monterey Bay area

Approaches to each of the above components vary throughout the nation. Approaches used in the Monterey Bay area are summarized here. First, a list is given of the approved TMDLs that are considered in this summary. This is followed by a summary of approaches used within these TMDLs, organized according to the different components of a TMDL.

Regionally approved TMDLs considered in this summary

TMDLs for the Monterey Bay area approved by the CCRWQCB are listed below (a subset of the full list for the region).

  • Watsonville Slough Pathogens TMDL[5]
    • Approved at the Federal, State and Regional level
  • Pajaro River (Including San Benito River, Llagas Creek and Rider Creek) Sediment TMDL[6]
    • Approved at the Federal, State and Regional level
  • Pajaro River (Including Llagas Creek) Nitrate TMDL [7]
    • Approved at the Federal, State and Regional level
  • San Lorenzo River (Including Carbonera Creek, Lompico Creek, and Shingle Mill Creek) Sediment TMDL [8]
    • Approved at the Federal, State and Regional level
  • Las Tablas Creek and Lake Nacimiento Mercury TMDL [9]
    • Approved at the Regional level only.
  • Basin Plan: Water quality objectives given in the Basin Plan [10]. Water quality objectives for the Basin Plan are attempts to quantify the allowable nutrient concentrations; regulatory agencies use objectives listed in the Plan as a starting point during TMDL development and adoption.

Approaches to Problem Identification

On the Central Coast of California, listings on the 303(d) list have been based on the specific water quality objectives contained within the Basin Plan for the region. Once water bodies have been listed, the state prioritizes them for TMDL development. The TMDL should include a problem statement, which is a description of the waterbody/watershed setting, beneficial use impairments of concern, and pollutants or stressors causing the impairment [11]. Information used to prepare problem statements for approved TMDLs in the Monterey Bay is summarized below.

Pajaro River Watershed [6]

  • Pajaro River and Llagas creek were listed as impaired by sediment on the 1998 Section 303(d) based on qualitative assessment of turbidity [12]. The 303(d) listing report did not specify which beneficial uses were affected.
  • Rider Creek was listed as impaired by sediment/siltation based on the sediment budget analysis which found sediment being exported to Corralitos Creek, and degrading steelhead rearing habitat [13]
  • San Benito River was found to be sediment starved, and causing accelerated downcutting and increased headwater incision [14] . It was listed as impaired by sediments.
  • Assessment of nitrate concentration was used to check the quality of municipal and domestic water supply.[7]

San Lorenzo River Watershed[8]

  • Counts of endangered and threatened fish populations of steelhead trout and Coho salmon were shown to be in decline.
  • San Lorenzo River, Carbonera Creek, Lompico Creek and Shingle Mill Creek were identified as impaired by sediment due to negative impact to beneficial uses associated with anadromous fisheries.
  • Municipal water suppliers were stated to have shut down the intake facilities during the periods of high flows because the facilities' filtering capacities were overwhelmed by excessive turbidity and sedimentation.

Watsonville Slough (no explicit problem statement section) [5]

  • Section 3.5 of Watsonville Slough TMDL states that water quality objectives for water contact recreation beneficial use (REC1) were routinely exceeded in several locations.
  • Wet and dry season sampling for fecal bacteria was used to confirm the existence of a potential pathogen problem in the water body.

Las Tablas Creek and Lake Nacimiento[9]

  • Basin Plan and California Toxics Rule objectives were stated to have been exceeded with respect to mercury in the waters of Lake Nacimiento and Las Tablas Creek.
  • Total Nickel Content in Klau Branch tributaty of the S. Fork Las Tablas Creek was stated to have exceeded Basin Plan Water Quality Objectives.

Approaches to developing Numeric Targets

Approaches to developing numeric targets in TMDLS differ depending on the pollutant being targeted.

Approaches to developing Numeric Targets for Pathogens

Pathogen levels are often quantified in terms of their most probable number (MPN) per unit volume of water. This metric is used in the Escherichia coli (E. Coli) TMDL standard developed for Watsonville Sloughs [5]. The TMDL numeric targets for E. coli in Watsonville Sloughs are:

  • Geometric mean 200MPN/100ml (min of 5 samples per 30 days)
  • Maximum of 400MPN/100ml (not more than 10% of samples per 30 days)

For more information on pathogen TMDL development, see The United States Environmental Protection Agency "Protocol for developing pathogen TMDLs"[15].

Approaches to developing Numeric Targets for Sediment

Sediment TMDLs use a different approach. For the Monterey Bay area, annual total sediment load by weight is used to describe TMDL numeric targets. Sediment has two categories, uncontrollable (natural or background) and controllable. TMDLs target the controllable portion of sediment and include the natural levels in the equation. To better define the sediment load a watershed may release, the watershed can be divided into sub- watersheds to determine each sub-region's allowable contribution to the whole. For the Monterey Bay Region, two separate sediment TMDLs have been developed:

  • Pajaro River (Including San Benito River, Llagas Creek and Rider Creek) Sediment TMDL[6]
    • Tres Pinos - 53,778 metric tons/year
    • San Benito - 39,679 metric tons/year
    • Llagas - 9,185 metric tons/year
    • Uvas - 15,177 metric tons/year
    • Upper Pajaro - 43,951 metric tons/year
    • Corralitos (including Rider Creek) - 11,389 metric tons/year
    • Mouth of Pajaro - 7,268 metric tons/year
  • San Lorenzo River (Including Carbonera Creek, Lompico Creek, and Shingle Mill Creek) Sediment TMDL [8]
    • Shingle Mill Creek- 857 tons/year
    • Carbonera Creek - 11,728 tons/year
    • Carbonera Creek - 9,542 tons/year
    • San Lorenzo River - 306,139 tons/year

For more information on sediment TMDL development, see The United States Environmental Protection Agency "Protocol for developing sediment TMDLs"[16]

Approaches to developing Numeric Targets for Nutrients

Nitrate levels are usually measured in mg/l nitrate-N. Since the United Stated Environmental Protection Agency Title 40 part 141.23[17] regulates nitrate not to exceed 10mg/l of nitrate-N, this is a common TMDL numeric target applied to watersheds. An example in the Monterey Bay Region can be found in the Pajaro River (Including Llagas Creek) Nitrate TMDL report[7] This report concludes:

  • Nitrate in Pajaro River and Llagas Creek is set at a maximum concentration of 10 mg/l nitrate-N

For more information on nutrient TMDL development, see The United States Environmental Protection Agency "Protocol for developing nutrient TMDLs"[18]

Approaches to developing Numeric Targets for Metals

Toxic metals can be either suspended or present in sediment, therefore they must be monitored both in the water column and within the sediment. Mercury, as an example in Las Tablas Creek and Lake Nacimiento [9] includes both water quality and sediment targets in its TMDL:

  • The Cal/EPA 40 CFR Part 131[19], also called the "California Toxic Rules" regulates mercury in water at 0.05 μg/L. This is the targeted water quality TMDL.
  • For sediment, the proposed TMDL target for mercury is 0.486 mg/kg. This target is based on the National Oceanic and Atmospheric Administration Permissible Exposure Limits (NOAA PEL)

Approaches to Source Analysis

The objective of the source analysis is to evaluate the type, magnitude and location of sources. This involves the combination of various modeling, monitoring and modeling techniques to determine nutrient inputs. Results from the source assessment are used to formulate load allocation of the TMDL. A summary of the approaches that have been used to identify and analyze potential sources in TMDLs approved so far in the California Central Coast Region are listed below.

Watsonville Slough Pathogens TMDL[5]

  • Initial Source Tracking
    • Initial monitoring : sampling
    • Increased monitoring to problem areas to isolate and identify sources: focused grab sampling and dye testing
  • Genetic Analysis
    • Toxic Gene Biomarker Method
      • DNA extraction of E. coli colonies on agar plates in water grab samples
      • DNA analysis for presence/ absence of toxin genes specific to host animals
  • Hydrologic Modification Analysis
    • Analysis of potential relationships between waterbody circulation and bacteria concentration
  • Land Use Distribution Analysis
    • Analysis of potential relationships between land use in subwatersheds with exceedences of water quality objectives

Pajaro River (Including San Benito River, Llagas Creek and Rider Creek) Sediment TMDL[6]

  • Integrated quantitative past source identification with analysis by Tetra Tech
    • Past source identification analysis consisted of the collection and analysis of sediment data
    • Tetra Tech used the Soil and Water Assessment Tool (SWAT) computer model to quantify sediment sources

Pajaro River (Including Llagas Creek) Nitrate TMDL [7]

  • Land use based approach
    • Use of multi-resolution datasets to identify land cover type
    • Sample data collection
    • Pollution load equation in ArcGIS to calculate nonpoint sources of pollution in watersheds.
      • PLOAD Version 3.0

San Lorenzo River (Including Carbonera Creek, Lompico Creek, and Shingle Mill Creek) Sediment TMDL [8]

  • Sediment source and sediment production data was used to estimate erosion rates, delivery ratios and sedimentation rates.
    • Sediment source data derived from GIS layers obtained from Santa Cruz County’s Environmental management information system (SCC EMIS)
    • Sediment production data derived from
      • Field data collected on roads and landslides
      • Field data collected for stream bank erosion
      • Extrapolation of field data and sediment production estimates

Las Tablas Creek and Lake Nacimiento Mercury TMDL [9]

  • Developed a Mercury loading model based on a geographical information systems (GIS) database combined with chemical sample data (Mercury loading model and chemical sample data from Rice et al. 2004)
    • Estimated basin and sub-basin areas using GIS and Calwater 2.2 basin outlines
    • Estimated mercury concentration for each area
    • Summed annual mercury loads for each sub-area to create a mercury load model

Approaches to Linkage Analysis

Linkage analysis involves examining and establishing cause-and-effect connections between the pollutant sources and the water quality targets. This linkage can be established through a combination of long-term monitoring data analysis, simulation models, best professional judgment, and previously established relationships. The association between pollutant sources and water quality targets established by the linkage can be used to estimate the pollution load capacity of the watershed. This load capacity is the quantity of pollution (load) that the watershed can withstand while also sustaining designated beneficial uses. Once calculated, the predicted pollutant load for the watershed must be validated for accuracy and precision. The product of the validation will be to assign all predictions an associated estimation of uncertainty. After the allowable pollution load is estimated, it can be divided up among the various sources in the watershed.

When evaluating linkages between pollutant sources and water quality targets, there are several points to consider:

  • Given the indicator to be evaluated, availability of monitoring data, watershed/waterbody hydrology and temporal and spatial variation:
    • What scale of complexity is most appropriate for the analysis?
    • What are the advantages and disadvantages for various approaches?
  • What available present and previous relevant monitoring data exists for this watershed/waterbody?

The United States Environmental Protection Agency (EPA) described several approaches for linkage analysis:

  • Approaches described for Source Analysis
  • Concentration and Response relationships (simplified systems)
  • Complex simulation models including:
    • Hydrodynamic and water Quality Model for Streams (CE-QUAL-RIVI)
    • Enhanced Stream Water Quality model (QUAL2E)
    • WASP5 modeling system for predicting transport and fate of pollutants in surface waters
    • EUTROMOD spreadsheet-based watershed and lake modeling system
    • PHOSMOD stratified lake phosphorous-loading model
    • BATHTUB eutrophication models for lakes and reservoirs with complex shapes
    • CE-QUAL-Q2 two dimensional water quality model
    • Hydrological Simulation Program FORTRAM (HSPF)
    • CE-QUAL-ICM 3-dimentional, detailed algorithm-based water quality kinetics model

Examples of Linkage Analysis approaches employed in the Monterey Bay Region of California include:

  • Pajaro River (including Llagas Creek, Rider Creek and San Benito Creek) sediment TMDL[6]
    • Combined suspended soil concentration into the Soil and Water Assessment Tool (SWAT) to link sediment sources to in-stream indicators, determine existing sediment loads, and evaluate optimal TMDL load reductions
    • Statistical analyses of stream bed characteristics (including pool volume and mean gravel size) to estimate watershed disturbance
  • Pajaro River (including Llagas Creek) nitrate TMDL[7]
    • Insufficient data collected for linkage analysis.
  • Watsonville Slough pathogen TMDL [5]
    • Incomplete linkage analysis
  • Chorro Creek Nutrients and Dissolved Oxygen TMDL [20]
    • Employed a combination of monitoring data, statistical analysis and best professional judgement
  • San Luis Obispo Creek Nitrogen-as-Nitrate TMDL[21]
    • Linkage analysis incomplete
  • Los Osos Creek, Warden Creek, and Warden Lake Wetland Nutrients TMDL[22]
    • Linkage analysis incomplete
  • San Lorenzo River (including Carbonera Creek, Lompico Creek, and Shingle Mill Creek) Sediment TMDL [8]
    • Statistical analyses of stream bed characteristics (including pool volume, mean gravel size and percentage fines and coarse fines) to estimate watershed disturbance.

Approaches to ...

Could consider inserting sections here on:

  • Approaches to 'TMDL Development'

CSMW is working closely with the State and Regional Water Quality Control Boards to facilitate the fluvial transport of coarse sediment needed to replenish coastal beaches while keeping fine-grained sediment contained so that it doesn't result in adverse impacts to fluvial, riparian or coastal habitats.Development

  • Approaches to developing a 'Margin of Safety'
  • Approaches to considering 'Critical conditions and seasonal variation'

...since sections on these TMDL components occur in Monterey Bay area TMDLS.

Approaches to developing Load Allocations

Load allocations indicate the amount of pollutant reduction that is required to attain specified water quality standards. Allocations may be assigned based on land use, land area, or erosional process. The regulations at 40 Code of Federal Regulations (CFR) 130.2(g) state that “Load allocations are best estimates of the loading, which may range from reasonably accurate estimates to gross allotments, depending on the availability of data and appropriate techniques for predicting the loading.” Not all TMDL allocations are in the form of load. The regulations at 40 CFR 130.2 (i) state "a mass load of the pollutant can also be expressed as a unit of concentration."

The techniques used to allocate new water quality standards vary between TMDL's. Below is a list of some of the of approaches to load allocation used in the California Central Coast Region.

  • Pajaro River (Including Llagas Creek) Nitrate TMDL [7]
    • Load Allocation: The nitrate TMDL is set at a maximum concentration of 10 mg/l nitrate-N in receiving water
    • Specific Sources: Load allocations of 10 mg/l nitrate-N are assigned to each source, including background and all watershed land uses
  • Pajaro River (Including San Benito River, Llagas Creek and Rider Creek) Sediment TMDL[6]
    • Load Allocation:
      • Suspended Sediment: The numeric targets are based on exposure index (concentration and duration) developed by Newcombe and Jensen.
      • Stream Bed Characteristics: Numeric targets were established for four stream bed parameters. The parameters are residual pool volume, median gravel size in spawning gravels, %fine material for fine fines and %fine material for coarse spawning gravel.
    • Specific Sources:
      • Suspended Sediment: Due to varying natural suspended sediment conditions through out the watershed individual sub-basins were assigned unique load allocation numbers.
      • Stream Bed Characteristics: The Pajaro River including Llagas, Rider and San Benito creeks are all considered one source. All of the listed stream bed parameters exists across the different sources.

  • Watsonville Slough Pathogens TMDL[5]
    • Load Allocation: The numeric target includes a maximum concentration and geometric mean. Maximum Concentration: No more than 10% of total samples during a period of 30days can exceed a fecal coliform concentration above 400 MPN/100ml. Geometric Mean: The geometric mean of no less than five samples over a period of 30 days exceed a concentration of 200 MPN/100ml.
    • Specific Sources: The numeric targets apply to all samples collected in the Watsonville Slough and including Gallighan, Harkin, Hanson and Struve Sloughs.

  • San Lorenzo River (Including Carbonera Creek, Lompico Creek, and Shingle Mill Creek) Sediment TMDL [8]
    • Load Allocation: Allocations are in the form annual loads.
    • Specific Sources: Allocations were divided between each sub-basin (Shingle Mill Creek, Carbonera Creek, Lompico Creek and San Lorenzo River. For each sub-basin load sources were divided between Upland THP Roads, Streamside THP Roads on Steep Slopes, Upland Public/Private Roads, Streamside Public/Private Roads on Steep Slopes, THP Land, Other Urban and Rural Land, Mass Wastig and Channel/Bank Erosion.

  • Las Tablas Creek and Lake Nacimiento Mercury TMDL [9]
    • Load Allocations: allocations are in the form of annual load.
    • Specific Sources: There are three sources that were specified, General Soils, Roads and Mines.

Approaches to developing a Monitoring and Evaluation Plan

Monitoring is required to identify impaired waters, prioritize clean up plans and provide feedback on effectiveness of TMDL implementation. A monitoring and evaluation plan should indicate monitoring goals and hypotheses, parameters to monitor, the monitoring methods to use, schedule for review and potential revision, and the parties responsible for implementing the plan. The plan must contain incremental, measurable targets consistent with implementation actions and the time frame for implementing those actions. For further detail, refer to EPA Protocols document

Several approaches to specifying a monitoring plan have been adopted in federally approved TMDLS in the Monterey Bay area.

  • Watsonville Slough pathogen TMDL:[5]
    • 8 monitoring locations specified to evaluate attainment and allocations of TMDL, 5 grab samples from each site collected over a 30 day period in early wet season, late wet season and dry season.
    • Potential sources at each location share responsibility for monitoring- City of Watsonville and Santa Cruz County stormwater outfalls and landfills, livestock operators and manure applicators.
    • Monitor for at least 3 years. Water Board will determine the need to continue or modify requirements. Monitoring results incorporated into MS4 Stormwater Permit and Waste Discharge Requirement annual reports.
  • Pajaro River sediment TMDL:[6]
    • No specific monitoring program exists to measure sediment numeric target.
    • Water Board staff relay on site assessment, photo documentation and annual reporting required by Agricultural Waiver Program for Irrigated Agriculture, Timber Harvest Monitoring Plan for forested land, monitoring and reporting by municipalities for Stormwater Program, and monitoring plans required for sand and gravel mining activities.
    • Monitoring plan needs to be developed within 5 years and will build upon existing monitoring. Monitoring data reviewed every 3 years for regional stormwater permit. Additional monitoring can be requested under section 13383 of California Water Code.
  • Pajaro River nitrate TMDL: [7]
    • Monitoring plan measures progress of attaining nitrate TMDL target and evaluates impairment due to excessive algae and low dissolved oxygen.
    • For Irrigated lands, landowners are resposible for monitoring nitrate under Agricultural Conditional Waiver. South County Wastewater Authority monitors nitrate according to Wastewater Discharge Requirements.
    • Water Board staff will develop and conduct algae and dissolved oxygen monitoring plan, including chemical, physical and biological data collection. Monitoring will be designed to determine what metric should be used to evaluate excessive algae, what level of algae should be considered excessive, what is the frequency, duration and spatial extent of algae, what are contributing factors to algal growth, does algae impair beneficial uses, and are low dissolved oxygen conditions a result of algae or other chemical or physical characteristics.
    • Monitoring results reviewed every 3 years. If studies result in improved information to evaluate exceedence algae, numeric targets for algae impairment will be set and if appropriate, a separate TMDL to address algal growth and low dissolved oxygen.
    • If data do not show algal exceedence and nitrate numeric targets and allocations are attained, waterbody will be de-listed for nutrient impairment.
  • San Lorenzo Rver sediment TMDL: [8]
    • Monitoring plan is designed to determine numeric targets are met, to track completion of implementation actions and to expand information upon which future actions will be based.
    • Santa Cruz County is responsible for monitoring effectiveness of erosion controls and physical factors influencing local sedimentation and salmonid habitat quality.
    • City of Santa Cruz Water Department and San Lorenzo Water District are responsible for conducting continuous turbidity trend monitoring.
    • Numeric target monitoring takes place at mouths of tributaries, at monthly intervals during low flow conditions. Bed sedimentation, stream geomorphology, bank erosion and stream flow is monitored in mainstem and tributaries at intervals of 1 to 5 years.
    • Monitoring of sediment and habitat-related parameters are coordinated through the county-led San Lorenzo River Technical Advisory Committee (TAC). TAC reviews data annually and evaluates effectiveness of existing implementation efforts.
    • Every 3 years Regional Water Board staff reviews monitoring data, determines TMDL compliance and considers changes to monitoring.

The following organizations have contributed monitoring data for Monterey Bay area:

Approaches to developing Implementation Plans

The purpose of an Implementation Plan is to describe the steps necessary to reduce pollutant loads to achieve these TMDLs. Implementation Plans identify the following: 1) actions expected to reduce pollutant loading; 2) parties responsible for taking these actions; 3) regulatory mechanisms by which the Central Coast Water Board will assure these actions are taken; 4) reporting and evaluation requirements that will indicate progress toward completing the actions; 5) a timeline for completion of implementation actions. Implementation Plans also address economic considerations to achieve compliance. Several approaches to specifying a monitoring plan have been adopted in federally approved TMDLS in the Monterey Bay area.

  • Watsonville Slough Pathogen TMDL:[5]
    • The cities of Watsonville and Santa Cruz are required to participate in public education through outreach.
    • City and county sewer systems must prioritize maintinence to reduce potential sources of pathogens.
    • Propery owners, and residence within Watsonville slough watershed and contributing tributaries must reduce or eliminate all potential pet waste that may enter waterbodies.
    • Just as pet waste must be regulated so must livestock waste.
  • Pajaro River Sediment TMDL:[6]
    • A NPS Implementation plan must identify the beneficial uses and water quality requirements the plan is designed to address.
    • Implementation plan must identify and describe the management practices to be employed.
    • Implementation time schedule must be provided.
    • Proper reporting, monitoring, and inspection requirements must be defined.
    • Outline of potential consequences of failure must be provided
  • Pajaro River Nitrate TMDL: [7]
    • Landowners of crop/orchard land must manage and monitor according to the conditional waiver.
    • Landowners of pasture/range land will use management practices from the Nonpoint Source Pollution Control Program, and the Rangeland Water Quality Management Plan.
    • Urban land areas within the local municipalities are all participants of the National Pollutant Discharge Elimination System (NPDES). Each municipality is responsible for following individual implementation methods, time schedules,a nd reporting requirements.
  • Pajaro River Fecal Coliform TMDL (including Pajaro River, San Benito River, Llagas Creek and Tequisquita Slough)
    • The implementation plans for the rivers within the Pajaro River TMDL require compliance with the Human Fecal Material Discharge Prohibition and the Domestic Animal Waste Discharge Prohibition.
    • Municipal storm sewer systems are to implement source identification and prioritization of fecal coliform sources.
      • Report when best managment practices are progressing towards achieving the waste-load allocations.
      • Coordinate with stakeholders.
  • San Lorenzo River sediment TMDL: [8]
    • Landowners of crop, fallow, orchard, and forest lands are to manage and monitor sources of sediment in accordance with the conditional ag waiver.
    • Pasture and range land owners must comply with land disturbance prohibition.
    • Cities must obtain a municipal Separate Storm Sewer System permit, and include specific actions to reduce sediment discharge.
    • Owners of property where hydro-modification has occurred must comply with the land disturbance prohibition.

  • San Lorenzo River Watershed Pathogen TMDL [23]
    • SLV watershed subjected to Human Fecal Material Discharge (HFMD) Prohibition and Domestic Animal Waste Discharge (DAWD) Prohibition
      • Cities of Santa Cruz and Scotts Valley are required to prevent any spills and leaks from their sewer systems pursuant to their NPDES permits. Immediate cessation is required of any leaks detected from private owners of lateral entries to the sewer systems.
      • Private homeowners are responsible for the maintenance of onsite wastewater disposal systems (septic systems) and must also demonstrate compliance with the prohibition.
      • Any landowners or operators of lands containing domestic animals (including pets, farm animals, and livestock) must provide evidence of compliance with the prohibition and submit a plan for future compliance. Any discharge must be reported or they must obtain an NPDES permit.
    • Urban runoff discharge controlled through the development and implementation of Storm Water Management Plans. these plans are required to target sources of Fecal Indicator Bacteria in urban runoff through the incorporation of wasteload allocation attainment programs. The City of Santa Cruz has installed pumps to divert dry weather stormwater discharges to the wastewater treatment system in order to improve the San Lorenzo Estuary water quality in summer months.
  • Lower Salinas River Watershed Fecal Coliform TMDL[24]
    • County of Monterey and City of Salinas, under the State Water Resource Control Board’s General Permit for Discharges of Storm Water from Municipal Separate Storm Sewer Systems, must develop a Storm Water Management Plan to control urban runoff and incorporate a Wasteload Allocation Attainment Program.
    • Lands containing domestic animals (pets, farm animals, and livestock) within the lower salinas river watershed (from Gonzales Rd to Moss Landing Harbor) subject to comply with DAWD prohibition
    • Lands containing homeless encampments must comply with the HFMD prohibition
    • Dumping of waste is illegal in Monterey County and the health department responds to illegal dumping complaints, files reports for investigation and engages in public outreach and education. The City of Salinas prosecutes individuals caught dumping waste and has established watershed cleanup efforts along City creeks. Citizens can report illegal dumping via a telephone hotline and financial rewards are given for reporting.
    • The City of Salinas, Castroville Community Services DIstrict and California Utilities Service Wastewater Treatment Plant (WWTP) are required to improve maintenance of sewage leaks in portions of the collection systems that are adjacent to impaired waters or their tributaries in the Lower Salinas watershed.
    • Cool Pacific Land Company, UNI-KOOL Salinas Facility and Abbot Street Facility, and Versacold Logistics must comply with fecal indicator bacteria monitoring requirements as permitted point sources under the CCWB general permit.
    • The California Utilities WWTP has not yet been a major source of fecal indicator bacteria into impaired water bodies, but will be monitored as a potential threat to El Toro Creek.
  • Aptos/Valencia Creek Pathogen TMDL[25]
    • County of Santa Cruz, under the State Water Resource Control Board’s General Permit for Discharges of Storm Water from Small Municipal Separate Storm Sewer Systems(MS4), must develop a Storm Water Management Plan(SWMP) to control urban runoff and incorporate a Wasteload Allocation Attainment Program. Leaks from privately owned sewer Laterals will also be addressed under this Wasteload Allocation Attainment Program.
    • Santa Cruz County Sanitation District must improve the maintenance of the sewage collection system that is near any impaired surface waters in the Aptos Creek Watershed. They must submit a technical report describing improvement measures and stream monitoring of fecal indicator bacteria.
    • lands containing or used for domestic animals (both pets and livestock) required to comply with the DAWD prohibition.
  • Corralitos Creek Pathogen TMDL[26]
    • County of Santa Cruz and City of Watsonville, under the State Water Resource Control Board’s General Permit for Discharges of Storm Water from MS4s, must develop a SWMP to control urban runoff and incorporate a Wasteload Allocation Attainment Program.
    • Santa Cruz County has an ordinance that enforces pet waste pick-up that is effective in public places, and an educational program for residents adjacent to riparian areas and waterbodies to decrease pollution from domestic pet waste.
    • Owners of lands containing homeless persons or Onsite Wastewater Systems (septic), or private laterals connecting to the sewer system along the Corralitos and Salsipuedes Creeks must demonstrate compliance with the HFMD prohibition.
    • Owners of lands used for or containing domestic animals along the Corralitos and Salsipuedes Creeks must comply with the DAWD prohibition.
    • Santa Cruz County and City of Watsonville need to develop strategies to address dumpster and receptacle leachate, leaks from private laterals, and new development practices. It is recommended by Central Coast Water Board staff that they target their public education and outreach program to address these issues.
  • Soquel Lagoon Pathogens TMDL[27]
    • Soquel creek watershed also added to list of watersheds subject to HFMD and DAWD prohibitions.
    • Santa Cruz County Sanitation District must improve maintenance of the sewage collection systems in order to prevent leaks in areas adjacent to Soquel creek
    • County of Santa Cruz and City of Capitola must create storm water management plans that comply with the Wasteload Allocation Attainment Program from the Central Coast Water Board

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Numeric targets are concentrations of specified nutrients that would not impair designated beneficial uses of a given water body. Water quality objectives given in the Basin Plan [10]. Water quality objectives for the Basin Plan are attempts to quantify the allowable nutrient concentrations, objectives listed in the Plan are used as a starting point during TMDL development and adoption.

Margin of safety (MOS)

The margin of safety in the Monterey Bay region compares to other regions as being (more/less/equally?)… in terms of assumptions made of the environmental system.

Some examples of reports that used conservative estimates include:

The San Louis Obispo Creek TMDL Report used the quantitative approach and estimated the margin of safety to be about 20% of the total nitrate-N mass load based on a number of uncertainties and limitations in their data.

The Malibu Report Malibu Creek watershed TMDL report also estimated a 20% margin of safety and implicitly included conservative assumptions into the TMDL analysis. However, it is this TMDL report has not yet been approved on the state or federal level (UPDATE FOR 2012).


Several approaches to specifying a monitoring plan have been adopted in federally approved TMDLs in the Monterey Bay area

Examples of approaches to implementation found in similar regional TMDL reports

  • Laguna de Santa Rosa Nutrient TMDL: the Waste Reduction Strategy includes: a grant program aimed at reducing waste inputs from confined animal operations, a storm water runoff program, an NPDES permit program, and voluntary actions organized by the Laguna Watershed Coordinated Resource Management and Planning Task Force.
  • San Luis Obispo Creek Nutrient TMDL: the NPDES permit for the City of San Luis Obispo will incorporate an effluent limit for their NPDES permit, regulations for storm water through a small MS4 permit, cropland nitrate sources will be regulated and monitored through the Ag Waiver.
  • Santa Clara River Nitrogen TMDL: Ammonia, nitrite, and nitrate reductions will be regulated through denitrification upgrades to Publicly Owned Treatment Works (POTW) and enforcement of effluent limits, NPDES permits, and agricultural Best Management Practices.

Examples of TMDLs

The Lower Salinas River Watershed Nutrient TMDL Progress Report has summarized procedures to develop numeric targets for nutrient loading reductions (see above) in impaired water bodies, but did not provided recommended LAs. TMDLs in other parts of California provide examples of different approaches used to set TMDL allocations:


  1. Central Coast Regional Water Quality Control Board. 2009. Clean water act sections 305(b) and 303(d) integrated report for the Central Coast region. Public review draft April.
  2. List of Water Quality Limited Segments Requiring TMDLs.
  3. 3.0 3.1 3.2 Killam G. 2005. The Clean Water Act Owner's Manual. Oregon: River Network.
  4. EPA Protocols for developing nutrient TMDLs
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Watsonville Slough Pathogens TMDL - Final Project Report, DRAFT.
  6. 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Pajaro River (Including San Benito River, Llagas Creek and Rider Creek) Sediment TDML - Final Project Report.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 7.6 7.7 Pajaro River Nitrate (Including Llagas Creek) TDML - Final Project Report.
  8. 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 San Lorenzo River (Including Carbonera Creek, Lompico Creek, and Shingle Mill Creek) Sediment TMDL - Report.
  9. 9.0 9.1 9.2 9.3 9.4 Las Tablas Creek and Lake Nacimiento Mercury TMDL - Draft Report.
  10. 10.0 10.1 [1].
  11. [ EPA Region 10 TMDL process overview
  12. The Establishment of Nutrient Objectives, Sources, Impacts, and Best Management Practices for the Pajaro River and Llagas Creek, San Jose State University 1996
  13. Rider Creek Sediment Management Plan, Santa Cruz County, California WRC Environmental, 1991
  14. Qualitative and Quantitative Analysis of Degradation of the San Benito River, Golder Associates, 1997
  15. US EPA Protocol for Developing Pathogen TMDLs
  16. [2]US EPA Protocol for Developing Sediment TMDLs.
  17. [3]US EPA Title 40 PART 141 National Primary Drinking Water Regulations.
  18. [4]US EPA Protocol for Developing Nutrient TMDLs.
  19. [5]California Environmental Protection Agency 40 CFR Part 131 Water Quality Standards; Establishment of Numeric Criteria for Priority Toxic Pollutants for the State of California; Rule.
  20. Chorro Creek Total Maximum Daily Loads for Nutrients and Dissolved Oxygen, Final Project Report November 2005.
  21. San Luis Obispo Creek Total Maximum Daily Loads for Nitrogen as Nitrate, Final Project Report June 2005.
  22. Los Osos Creek, Warden Creek, and Warden Lake Wetland Total Maximum Daily Loads for Nitrogen as Nitrate, Final Project Report June 2005.
  23. San Lorenzo River Watershed Pathogen TMDL.
  24. Lower Salinas River Watershed Fecal Coliform TMDL Final Report
  25. Aptos/Valencia Creek Pathogen TMDL Final Report
  26. Corralitos Creek Pathogen TMDL Final Report
  27. Soquel Lagoon Pathogens TMDL Final Report



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