ARCHIVED REPORTS_XR0002044 - Laserfiche WebLink

Home Browse Search

Beacon Station No 641 July 14 2000 Stockton California Quarterly Groundwater Monitoring Report r Groundwater samples were collected from all eight monitoring wells the sparge well and four of the eight vapor wells The groundwater samples were submitted under chain-of- custody documentation to Kiff Analyttcal (Kiff) a California-certified analytical laboratory (EL AP No 22;6) located in Davis California The groundwater samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg), the volatile aromatic compounds benzene toluene ethy lbenzene and total xylenes (BTEX) the seven fuel oxygenates meth}I tert-butt'1 ether (MTBE) diisopropyl ether (DIPS) ethyl tert-butyl ether (ETBE) tert-am,,1 methyl ether (TAME) tert-butanol (TBA) methanol and ethanol by Environmental Protection Agency (EPA) Method 8260B The laboratory data sheets and the chain-of-custody document are included as Attachment C Results Groundwater level data collected by Doulos were used to construct a groundwater contour map (Figure 2) Depth-to-groundwater measurements were subtracted from the surveved TOC elevations to calculate static groundwater elevations The average groundwater elevation was approximately 57 6 feet mean sea level and represents an approximately 0 5 foot rise compared to that measured in March 2000 The groundwater flow direction was generally northeast in the southwestern half of the site and southwest in the northeastern half of the site giving a gentle saddle shape to the water table Generally groundwater gradients across the site were approximately 0 005 Concentrations of TPHg ranging from 0 6 to 7700 micrograms per liter (parts per billion or ppb) were detected in monitoring wells MW-2, MW-4 MW-5 MW-7 and MW-8 vapor �. extraction wells VW-1, VW-3 'vW-5 and VW-7, and sparge well SW-1 The highest TPHg concentrations were reported in groundw ater samples from wells in the UST area Benzene was reported in groundwater samples from monitoring wells MW-2, MW-5 and MW-8, -vapor extraction wells VW-1 VW-3, VW-5 and VW-7 and sparge well SW-1 Benzene concentrations in monitoring wells MW-2 and MW-8, and sparge well SW-1 ranged from 0 6 to 3 I ppb Benzene concentrations in monitoring well MW-5 and -,apor extraction wells VW-I, V W-3 VW-5 and VW-7 in the UST area ranged from 800 to 7700 ppb Benzene concentrations have increased in all cases except for monitoring well MW-8 compared to March 2000 Benzene concentration data were used to construct a benzene isoconcentration map (Figure 3) Generally benzene concentration data from wells screened below the water table were not used to construct the benzene isoconcentration contours Concentrations of the fuel oxygenates DIPS and ETBE were not detected in any of the groundwater samples this quarter Concentrations of MTBE were reported in groundwater from all sampled wells except monitoring wells MW-7 and MW-8 at concentrations ranging 0 58 to 16,000 ppb Concentrations of MTBE have decreased in all groundwater samples except from vapor extraction wells VW-1 VW-3 and VW-5, compared to March 2000 Concentrations of TBA were detected in all groundwater samples except from monitoring 641gmr0002 doc 1641 43 2 HORIZON ENVIRONMENTAL INC