Overview of Total Maximum Daily Load (TMDL) Progress Assessment

EPA assessed the progress of implementing 14 Total Maximum Daily Loads (TMDLs) in the San Francisco Bay Delta Estuary (SF Bay Delta) to determine if the actions called for in the TMDL were being accomplished and water quality was improving. TMDL implementation refers to completing required TMDL actions, achieving load limits, and removing water quality impairments. These TMDL implementation assessments were called for in the EPA SF Bay Delta Action Plan (August 2012) to "…improve accountability and help align grant and program activities to ensure timely achievement of load limits and removal of impairments."

TMDLs chosen for evaluation address several aquatic life stressors including low dissolved oxygen, pesticides, selenium, and mercury. The first three of these contaminants and stressors are considered potential contributors to sharp declines in resident and migratory fish populations observed early in the 21^st century and low population numbers observed today. Mercury TMDLs were also evaluated because minimizing methylmercury production is essential for protecting public health, aquatic life, and aquatic-dependent wildlife.

All 14 TMDLs are being actively implemented and many milestones are being achieved. Eight of the TMDLs evaluated show that water quality conditions are improving or targets have been achieved, see Table 1. However, aquatic life beneficial uses continue to be impaired by contaminants and stressors despite these important water quality improvements. A progress report was produced and posted for each TMDL listed in Table 2.

TMDL Assessment Summary

Concentrations of two pesticides (diazinon and chlorpyrifos) have been substantially reduced in the SF Bay Delta watershed, however newer classes of pesticides are causing aquatic toxicity in these waterways.
Selenium load reductions have resulted in selenium concentrations that meet either final or interim TMDL targets in Salt Slough and the lower San Joaquin River while selenium concentrations continue to exceed the water quality objective in the Grasslands Marsh.
Dissolved oxygen conditions have improved in the Stockton Deep Water Ship Channel, but are not yet consistently meeting water quality goals for protecting migratory fish.
Mercury TMDLs are being implemented, however mine remediation actions and developing new methylation reduction technologies are solutions that require decades before mercury concentrations in fish tissue would achieve water quality goals.

Table 1: TMDL Implementation Assessment Summary
Status	# of TMDLs
Targets Achieved	4
Conditions Improving	4
Improvement Needed	6
Data Inconclusive	0

Table 2: EPA SF Bay Delta TMDL Progress Reports
Waterbody and TMDL Pollutant (EPA Approval Date)	Target Compliance Date	EPA Approval Date	Water Quality Status
Lower San Joaquin River Diazinon & Chlorpyrifos ⁴	2011-03	2006	TMDL Targets Achieved
Lower Feather River and Lower Sacramento River Diazinon & Chlorpyrifos ⁸	2010	2008	TMDL Targets Achieved
Salt Slough Selenium		1999	TMDL Targets Achieved
Lower San Joaquin River Selenium ²	2019	2003	TMDL Targets Achieved[1]
Stockton Deep Water Ship Channel in the San Joaquin River Low Dissolved Oxygen	2011-12-31	2007	Conditions Improving
Sacramento County Urban Streams Diazinon & Chlorpyrifos ³		2004	Conditions Improving
Sacramento-San Joaquin River Delta Diazinon & Chlorpyrifos	2012-03	2007	Conditions Improving
Grasslands Marshes Selenium		2000	Conditions Improving
Bay Area Urban Creeks Diazinon & Pesticide-Related Toxicity		2007	Improvement Needed
Clear Lake Mercury		2003	Improvement Needed
Cache, Bear, and Sulphur Creeks & Harley Gulch Mercury		2007	Improvement Needed
San Francisco Bay Mercury	2028	2008	Improvement Needed
Guadalupe River Watershed Mercury	2029	2010	Improvement Needed
Sacramento-San Joaquin Delta Estuary Mercury and Methylmercury	2030	2011	Improvement Needed

[1] Interim targets achieved, final target compliance date is not until December 2019.