April 25, 2005 Calleguas Creek Watershed Toxicity, Chlorpyrifos and Diazinon TMDL Technical Report Submitted to Los Angeles Regional Water Quality Control Board Prepared by Larry Walker Associates on behalf of the Calleguas Creek Watershed Management Plan Table of Contents TABLE OF CONTENTS.................................................................................................................................I LIST OF APPENDICES................................................................................................................................III LIST OF TABLES.........................................................................................................................................IV LIST OF FIGURES.......................................................................................................................................VI 1 INTRODUCTION ..................................................................................................................................1 1.1 REGULATORY BACKGROUND............................................................................................................3 1.2 CALLEGUAS CREEK TMDL STAKEHOLDER PARTICIPATION PROCESS..................................................3 1.3 ELEMENTS OF A TMDL ...................................................................................................................4 2 PROBLEM STATEMENT .....................................................................................................................5 2.1 ENVIRONMENTAL SETTING...............................................................................................................5 2.1.1 Arroyo Simi/Las Posas.............................................................................................................5 2.1.2 Conejo Creek...........................................................................................................................6 2.1.3 Revolon Slough........................................................................................................................7 2.1.4 Mugu Lagoon...........................................................................................................................7 2.1.5 Climate and Hydrology.............................................................................................................7 2.1.6 Surface Waters ........................................................................................................................8 2.1.7 Groundwater ............................................................................................................................9 2.1.8 Anthropogenic Alterations......................................................................................................10 2.1.9 Flow Diversion Project ...........................................................................................................11 2.1.10 Reach Designations ..........................................................................................................11 2.2 WATER QUALITY STANDARDS ........................................................................................................13 2.2.1 Beneficial Uses ......................................................................................................................13 2.2.2 Water Quality Objectives .......................................................................................................15 2.2.3 Antidegradation......................................................................................................................15 2.3 BASIS FOR LISTINGS .....................................................................................................................15 2.3.1 Water Column and Sediment Toxicity Listings.......................................................................16 2.3.2 Organophosphate Pesticides in Water Listing .......................................................................20 2.3.3 Chlorpyrifos in Fish Tissue Listings........................................................................................20 2.3.4 Use of EDLs to Form the Basis of 303(d) Listings .................................................................21 2.4 PROBLEM STATEMENT SUMMARY...................................................................................................22 3 CURRENT CONDITIONS...................................................................................................................23 3.1 USE OF ENVIRONMENTAL DATA IN CURRENT CONDITIONS SECTION ..................................................23 3.1.1 Development of Summary Statistics ......................................................................................24 3.2 CURRENT CONDITIONS BY REACH..................................................................................................26 3.3 ADDITIVE/SYNERGISTIC TOXICITY...................................................................................................43 3.4 WATER TOXICITY SUMMARY ..........................................................................................................44 3.5 SEDIMENT TOXICITY SUMMARY ......................................................................................................46 4 NUMERIC TARGETS .........................................................................................................................48 4.1 AMMONIA TARGETS ......................................................................................................................48 4.2 ORGANOCHLORINE PESTICIDES TARGETS.......................................................................................48 Calleguas Creek Watershed April 25, 2005 i Toxicity, Chlorpyrifos, and Diazinon TMDL 4.3 OP PESTICIDES (CHLORPYRIFOS AND DIAZINON) TARGETS..............................................................48 4.3.1 Chlorpyrifos Targets...............................................................................................................49 4.3.2 Diazinon Targets....................................................................................................................50 4.4 WATER TOXICITY TARGET .............................................................................................................52 4.4.1 Alternatives Considered for Water Toxicity Target.................................................................53 4.5 SEDIMENT TOXICITY TARGET .........................................................................................................53 5 SOURCE ANALYSIS .........................................................................................................................55 5.1 DATA RESOURCES........................................................................................................................55 5.1.1 Use of Environmental Data in Source Analysis Section.........................................................56 5.1.2 Development of Summary Statistics ......................................................................................56 5.1.3 Pesticide Use Data ................................................................................................................57 5.1.4 Pesticide Sales Data..............................................................................................................57 5.2 LAND USE ....................................................................................................................................58 5.2.1 Urban Land Use.....................................................................................................................59 5.2.2 Agricultural Land Use.............................................................................................................59 5.3 SOURCES OF DIAZINON AND CHLORPYRIFOS TO CALLEGUAS CREEK WATERSHED .............................61 5.3.1 Diazinon and Chlorpyrifos Use in Calleguas Creek Watershed .............................................61 5.3.2 Phase Out of Uses.................................................................................................................61 5.3.3 Agricultural Use......................................................................................................................64 5.3.4 Urban Use..............................................................................................................................71 5.3.5 Comparison of Agricultural, Urban, and Unreported Uses .....................................................78 5.3.6 Publicly Owned Treatment Works..........................................................................................79 5.3.7 Groundwater ..........................................................................................................................79 5.3.8 Atmospheric and Aerial Deposition........................................................................................79 5.3.9 Imported Water ......................................................................................................................80 5.3.10 Native Space Runoff..........................................................................................................81 SUMMARY .................................................................................................................................................82 6 LINKAGE ANALYSIS.........................................................................................................................84