ARCHIVED REPORTS XR0011755 - Laserfiche WebLink

Home Browse Search

Evaluation of Natural Attenuation: 7500 West Eleventh Street, Tracy, CA. Page ii 7.1 Primary Evidence of Natural Attenuation.......................................................................... 24 0 7.1.1 Attenuation of Analytes of Concern with Distance from the Source......................... 24 7.1.2 Attenuation of Analytes of Concern with Time................................... .. . ... 7.1.2.1 Time Required for Complete Remediation of Contaminants in Source Area..... 27 7.1.3 Mass Balance of BTEX in Groundwater.................................................................... 28 7.2 Secondary Evidence for Natural Attenuation..................................................................... 32 ! 7.2.1 Evidence for Aerobic Biodegradation........................................................................ 33 7.2.1.1 Dissolved Oxygen in Groundwater . 33 7.2.1.2 Oxidation Reduction Potential............................................................................ 34 f.l 7.2.2 Evidence for Anaerobic Respiration........................................................................... 34 7.2.2.1 Ferrous Iron in Groundwater................ ...................... ........... 35 7.2.2.2 Total Dissolved Iron............................................................................................ 36 p._j 7.2.2.3 Manganese..............................•.................... ..... 36 ................................................... 7.2.2.4 Sulfate.................................................................................................................. 37 7.2.2.5 Methane............................................................................................................... 37 i 7.2.2.6 Carbon Dioxide...................................... .... 37 . ....................................................... ! 7.2.2.7 Nitrates 7.2.3 Other Geochemical Indicators.................................................................................... 38 7.3 Summary of Evidence of Active Bioremediation............................................................L. 39 8.0 OPTIMAL MONITORING DATES AND FREQUENCY...............................................L-41 8.1 Optimal Monitoring Dates.................................................................................................41 8.2 Efficient Sampling Fre p g q uenc Y.................. .....43 i 8.2.1 ASTM Standard E 1943-98 Guidance.....................•. 8.2.2 US-EPA Guidance......................................................................................•...............43 8.2.2.1 MAROS Input Data.......................... ........................................................44 8.2.2.2 Plume Stability .... 44 8.2.2.3 Well Redundancy Analysis............................................. 8.2.2.4 Optimal Sampling Frequency..............................................................................47 8.2.2.5 Summary of MAROS Analysis...................... ........49 9.0 CONCLUSIONS........................................................................................ ........ 50 .................... ' t 10.0 RECOMMENDATIONS ..... 52 10.1 Technology for Groundwater Remediation....................................................................... 52 10.2 Groundwater-quality Monitoring Program 10.2.1 June 2005 -March 2006 Quarterly Monitoring......................................................... 52 .......................... 10.2.2 March 2006 MAROS Analysis.................................................................................. 53 10.2.3 Optimal Scope and Frequency of Long Term Monitoring . 53 10.2.4 Suite of Analytes to be Monitored............................................................................. 53 10.3 Monitoring of Potable Water Quality ............................................................................... 54 11.0 REFERENCES.......................................................................... TABLES 'i Table 1: Depths to Groundwater Table 2.- Results of Analyses of Samples of Groundwater jTable 3: Thickness of Floating Product in Monitoring Well MW-7 _J Table 4: Results of Analyses of Samples from Potable Water Wells Table 5: Natural Attenuation Data Sic