Status of Calleguas Creek Chloride TMDL October 22, 2002

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Status of Calleguas Creek Chloride TMDLOctober
22, 2002

• L. Donald Duke, Ph.D., P.E.
• Regional Water Quality Control Board, Los Angeles

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Los Angeles Regional Water Quality Control Board
Staff

• Don Duke 213-576-6806 dduke_at_rb4.swrcb.ca.go
  v
• Elizabeth Erickson
• Melinda Becker
• Jon Bishop

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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Proposed Water Quality Objectives
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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Calleguas Creek Water Quality Problems, Chloride

• 303(d) impaired listing in 1998
• Consent Decree requirements TMDL to be
  completed March 2001
• Growth of urban areas and agricultural use
• Water quality problems
• Chloride affects agricultural beneficial uses
• Chloride concentration has increased

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Historical Chloride Concentration, Calleguas
Creek System, 3 Areas
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Watershed Chloride Loading
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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Proposed Water Quality Objectives
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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WQO Specification

• WQO specified for each reach to protect
  beneficial uses
• existing beneficial uses
• local conditions
• Allowable load takes advantage of assimilative
  capacity pollutant load a waterbody can accept
  without affecting beneficial uses (i.e.,
  exceeding WQO)

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WQO Selection Cl- Concentrations and
Agricultural Beneficial Uses

• Rainwater 5-20 mg/L
• First Effect on Avocado 70-100
• Avocado Sustained Yield 100-120
• Average Crop Sustained Yield 140-160
• Avocado Damage 170-180
• Aquatic Life Drinking Water 230-250
• Seawater 18,000

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Proposed WQOs by Reach

• Where avocados are most Cl--sensitive 110
  mg/L (Arroyo Simi / Las Posas system)
• Where other crops control 150 mg/L (Remainder of
  watershed)
• Where groundwater recharge controls Protect most
  sensitive groundwater use

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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Proposed Water Quality Objectives
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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Critical Conditions Linkage Model
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Critical conditions Projected Effects of Flow
Diversion, Reach 9B
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Seasonality Monthly Average Flow, Three Locations
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Patterns of Daily Discharge at Conejo Creek
Gauge, Jan - Feb 1983
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Low Flow Percent by Month, Calleguas Creek at
Potrero Road
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Critical conditions used for Waste Load
Allocations

• Routine days Based on maximum non-storm flow
  and load
• Drought conditions Based on post-drought
  flow and load

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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Proposed Water Quality Objectives
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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TMDL Approach Allocating loads to meet WQOs
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Margin of Safety

• Implicit
• Conservative assumptions in LAs and critical
  flow conditions
• Explicit
• In-stream numeric target less than WQO ( target
  x 110 WQO )

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Basis, Proposed WLAs, North Routine
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Proposed WLAs Routine Conditions
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Proposed WLAs Drought Conditions
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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Proposed Water Quality Objectives
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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Implementation Summary

• Target in Arroyo Simi attainable with Cl-
  removal for major and minor dischargers
• Target in Conejo Creek usually attainable at
  Hill Canyon WWTF with present eqpt.
• Downstream impacts remedied by others
• Minor dischargers may need to use treatment eqpt.
• Calleguas Creek main stem target attainable with
  treatment at Camarillo WWTP / Camrosa WWRF
• Minor dischargers may need to use treatment eqpt.
• Brine line to carry saline waste
• Diversion of desalted water (lower Conejo)
  accommodated--minimum flow remains in stream

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Enforcement

• NPDES Permits
• Waste Discharge Requirements
• Pollution Prevention Plans
• Porter Cologne 13263.3(d)(1)

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Schedule for Proposed Actions

• TMDL and Technical Support Evaluations available
  for public comment October 2001
• Revised WQO adoption 2002
• TMDL adoption 2002
• Implementation Phased to brine line completion

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Concluding Summary

• WQOs determined by reach
• Critical conditions used to calculate WLAs
• Max. non-storm flow all days except storms
• Post-drought loadings all drought periods
• Implementation plan accommodates financially
  efficient remedy strategy
• Economic calculations project costs to be
  attainable, may be equitably distributed

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Basis, Proposed WLAs, South Routine
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Basis, Proposed WLAs, Calleguas Creek Main Stem
Routine Conditions
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Statistical calculations Drought
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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Selection of Numeric Targets
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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Calleguas Creek Chloride TMDL

• History Impaired Conditions
• Selection of Numeric Targets
• Critical Conditions
• Waste Load Allocations
• Implementation Plan

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Critical conditions Routine days

• Based on maximum non-storm flow/load
• Linkage modeled using flow/loads for critical
  ile flow (statistical method)
• Numeric targets determined specific to each
  reach depend on flow conditions, known variation
  of groundwater loads, WQOs

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Critical conditions Drought

• Based on post-drought flow/load
• Numeric targets specific to each reach depend on
  flow, groundwater loads, WQOs
• Begins June 1 when previous 12 months rainfall lt
  15ile distribution (11 inches)
• Ends June 1 when previous 12 months rainfall gt
  25ile distribution (12.2 inches)
• Distribution data NWS CA Zone 6

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Mass Balance Example Hill Canyon, Reach 10
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Beneficial UsesAgriculture

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Beneficial Uses Ecosystem and Human Health
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Assimilation of Waste
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Calleguas Watershed Reaches
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Summary of TMDL Results

• WLAs lb/day (mg/L at current flow)
• Simi Valley WQCP
• Ventura Co. WWTP
• Hill Cyn WWTF
• Camarillo WWTP
• Camrosa WWRF
• (show also reduction?)
• Minor dischargers Conc. equal to numeric target
  (WQO-MOS) for each reach

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Calleguas Creek System Reach Designations, Ben.
Uses, and WQOs

• Reach designations sources?
• WQOs selected by reach
• REFER TO MAP

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WLA Calculation Basis

• Achieve numeric target specified for each
  reach
• WLAs computed using LAs and flow during
  critical conditions
• Maximum non-storm routine days
• Post-drought drought periods
• In-stream explicit margin of safety 10