Laserfiche WebLink
a:. <br /> Supplementary Site Assessment Report <br /> Former Mobil Bulk Plant 04-343 <br /> April 26, 1996 <br /> ' hydrocarbon-impacted well (AW-3) with a well with non-detectable hydrocarbon concentrations <br /> (AW-9). The samples were submitted to a state-certified laboratory and analyzed for the <br /> ' following: <br /> ' • Heterotrophic plate count (HPC) using Standard Method 907 <br /> • Total organic carbon (TOC) using EPA Method 415.1 <br /> • CAM 17 Metals using EPA Method 200.7 <br /> ' pH using EPA Method 150.1 <br /> • Nitrites, nitrates, and phosphates using EPA Method 300.0 <br /> • Total dissolved solids using EPA Method 160.1 <br /> • Chemical oxygen demand using EPA Method 410.1 <br /> Refer to Appendix B for copies of the Official Laboratory Reports, QA/QC Reports, Chain of <br /> ' Custody Records, and field notes. <br /> 5.2.1 Bio-parameter Findings <br /> Dissolved-Oxyggn <br /> Aerobic biodegradation of petroleum hydrocarbons can occur at DO levels of 1 to 2 ppm, but <br /> occurs much more readily and rapidly at levels above 2 ppm. Below 1 ppm, anaerobic <br /> conditions exist. The DO present in groundwater at the site ranges between approximately 1 to <br /> 3 ppm. Concentrations in AW-3 were 1.81 ppm on August 16, 1995, and 1.6 ppm on October <br /> 24, 1995. These values are low; indicating that little aerobic degradation of the hydrocarbons <br /> is taking place. Introduction of oxygen into the wells could stimulate aerobic degradation if <br /> sufficient hydrocarbon degrading bacteria are present. During biodegradation, DO is consumed <br /> as aerobic respiration occurs, therefore a continual replenishment of oxygen to the aquifer would <br /> ' promote favorable conditions. <br /> Heterotrophic_Plate Count <br /> Heterotrophic plate count (HPC) is a term used for bacteria enumeration which is generally <br /> expressed as CFU/mL, colony forming units per milliliter. This includes hydrocarbon-degrading <br /> ' and non-hydrocarbon-degrading bacteria. Groundwater from Monitoring Well AW-9 contained <br /> 3,100 CFU, while AW-3 had a bacteria population of 67 CFU/mL. In general, 100 CFU/mL <br /> is considered to be sufficient for hydrocarbon biodegradation, therefore, the HPC determined for <br /> AW-3 appears to be low. <br /> 6 <br /> 1 <br />