A sediment total maximum daily load (TMDL) for the Sonoma Creek and its tributaries is required due to impairment of beneficial uses caused by land-use practices which have increased the rate of sediment production to streams. Adverse impacts associated with excess sediment production include degradation of salmonid habitat, loss of channel capacity, channel destabilization, and premature loss of reservoir storage.
Development and execution of the TMDL to resolve sediment related water quality impairment will be best accomplished through a stakeholder involvement forum. A stakeholder group has already been established for the Sonoma Creek watershed and the TMDL should be developed in concert with the existing stakeholder group.
The general approach for the sediment TMDL includes the following tasks. A compilation and review of existing data is needed, followed by development and implementation of a comprehensive watershed assessment and characterization plan, and a refinement of the impairment listing. The TMDL process will proceed with identification of pollutant sources and evaluation of their relative pollutant loads. A rapid sediment budget needs to be developed that includes the type and location of the major natural and land management related sources of sediment, and approximate amount of sediment contributed by each type of source.
Numeric targets specifying allowable sediment discharge rates and the desired quality of channel habitat conditions need to be established. Compliance monitoring and numeric targets will also need to be established for stream habitat attributes that are affected by sediment load and are biologically meaningful. An implementation plan that includes an allocation of responsibility will be developed. The TMDL will also include the development and implementation of pollution control strategies including compilation of Best Management Practices (BMP), education and outreach activities, and implementation of a verification/monitoring process to evaluate progress.