City of Trinidad - Storm Water Management Improvement Project, Preconstruction Water Quality Monitoring, Assessment & Reporting

Stormwater, receiving water, and sediment sampling locations map
Flow weighted water samples were collected from the City’s outfall and grab samples from the receiving water
Prime Contractor: 
Period of Performance: 
July, 2011
Project Description: 

In its 2003 final report, Discharges into State Water Quality Protection Areas, the State Water Resources Control Board (SWRCB) identified the City of Trinidad’s (City) stormwater discharge outfall as a High Threat Discharge to the Trinidad Head Area of Special Biological Significance (ASBS). In 2005, the SWRCB issued cease and desist orders (CDO) to stop all unpermitted discharges into ASBS, including stormwater.

In 2008, the City was awarded funding through the SWRCB’s Proposition 84 ASBS Grant Program funding to implement the Storm Water Management Improvement Project (Improvement Project) to partially address the City’s stormwater discharges.

The purpose of the Improvement Project is to implement enhancements to the City’s existing stormwater system that will help to protect the water quality and beneficial uses of the Trinidad Head ASBS. The project will divert a significant percentage of stormwater runoff into treatment and infiltration-to-ground Best Management Practices (BMP) and Low Impact Development (LID) technologies, resulting in reduced runoff volume and pollutant loading to the ASBS. Environmental sampling and analysis is required as an integral part of the Improvement Project in order to assess and evaluate the project’s effectiveness in reducing stormwater runoff volume and associated pollutant loading to the ASBS. This includes pre- and post-construction sampling of stormwater runoff, ocean receiving waters, and subtidal sediment to be performed during 2011-2012 and 2013-2014; storm water and receiving water samples will be collected during three storm events each wet season and sediment samples will be collected in the following spring.

Scope of Services: 


Per the Grant Agreement, ADH developed a Project Assessment and Evaluation Plan (PAEP), Quality Assurance Project Plan (QAPP) and Monitoring Plan (MP) in order to assess the project’s success in improving water quality within the ASBS. Based upon the MP, ADH developed and performed all technical aspects of the monitoring project including installation of stormwater flow monitoring and sampling equipment, field sampling, and contracting with accredited analytical laboratories for sample analysis. To date, ADH staff has performed all pre-construction monitoring, including the collection of continuous flow and rain data, flow-weighted stormwater sampling from the City’s outfall, receiving water sampling in the vicinity of the outfall, and subtidal sediment sampling from four locations in Trinidad Bay. Post-construction will be performed following completion of construction.

All water and sediment samples collected were/will be subjected to analytical testing for a comprehensive suite of physical and chemical analyses as specified by the QAPP. Analytical results were/will be evaluated to determine pre- and post-construction water and sediment quality characteristics. Results were/will be evaluated in respect to applicable state and federal criteria and guidelines, including the California Ocean Plan and National Oceanographic and Atmospheric Administration (NOAA) Sediment Quality Guidelines. An interim pre-construction sampling and analysis report has been prepared by ADH for the City and a final report on all pre- and post-construction monitoring, including stormwater quality, flow monitoring and pollutant loading will be prepared upon project completion.

The project is being performed in collaboration with the City and is being regulated by the SWRCB.