MTA Division 10 Groundwater Monitoring and Reporting, Los Angeles, California



Los Angeles County Metropolitan Transportation Authority (LACMTA)


Field visits to sites, Groundwater sampling, Well monitoring, Quarterly report preparation, Evaluation of results, Presentation of conclusions


This program provides data and evaluations necessary to satisfy the Regional Water Quality Control Board’s (RWQCB) quarterly groundwater monitoring and reporting requirements. DRC supported and implemented the existing Health and Safety Plan to protect all personnel and subcontractors at the site. Field activities consisted of quarterly monitoring and sampling of 12 groundwater monitoring wells at the site, beginning in May/June 2003 (2nd quarter) and continuing for four quarters (four rounds of monitoring and sampling). Each well was monitored for depth to groundwater and for floating hydrocarbons using an electronic well sounder and interface probe. Groundwater levels were measured to the nearest 0.01-foot relative to the top of the well easing to conform with procedures for previous measurements. Groundwater levels ranged from approximately 11 to 15 feet below ground surface. A new disposable bailer was used to collect groundwater samples. Each sample was decanted into sample jars. Natural attenuation parameters, including pH, specific conductance, temperature, dissolved oxygen, and oxidation-reduction potential, were monitored in the well after purging and sampling procedures. DRC prepared quarterly groundwater monitoring reports that described field procedures, measured ground water levels and water quality parameters during well purging, summarized laboratory analytical results, discussed the results, and rendered conclusions. Maps provided groundwater contours as well as the distribution of detectable groundwater contaminants. A registered Geologist signed all final reports.