ARCHIVED REPORTS_XR0012247 - Laserfiche WebLink

Home Browse Search

Mr. Nuel Henderson Page 2 of 4 The potentiometric surface was above the top of the screened intervals in monitoring wells MW4 through MW13B, MW15B, MW15C, MW16B and vapor wells VW1 and VW4. Vapor well VW5 was dry. Groundwater flowed in an east-northeasterly direction. The gradient across the site was approximately 0.002 feet per foot. A potentiometric surface map generated using the groundwater elevation data from all site groundwater monitoring wells is shown on Figure 2. Groundwater monitoring data are summarized in Table 1. Monitoring data sheets and well construction details are included in Attachment A. On February 25, 2004 through February 27, 2004 a Ground Zero technician collected groundwater samples from monitoring wells MW 1 through MW5, MW7, MW8, MW9, MW 12, MW13B, MW 14, MW 15A through MW15C, MW 16A and MW 16B; and from vapor wells VW 1 and VW3. A minimum of three well casing volumes was purged from each site well prior to sampling. During the purging process, physical parameters (pH, electrical conductivity, and temperature) were monitored. Subsequent to parameter stabilization, and a minimum of 90% recovery of initial depth to groundwater measurements, groundwater samples were collected and placed in an iced cooler for transport to Argon Laboratories (FLAP #2359) under chain of custody protocol. Analysis consisted of gasoline oxygenates, EDB and 1,2-DCA by EPA Method 8260B, TPHg by EPA Method 8015B and BTEX by EPA Method 8021B. Purge water was transferred into marked 55-gallon drums approved by the Department of Transportation (DOT). The waste is stored onsite within a secured area. Purge logs are included in Attachment A. GROUNDWATER ANALYTICAL RESULTS Groundwater Monitoring Wells TPHg and benzene were detected in all sampled wells except MW7, MW9, MW12 and MW15A through MW15C. Dissolved TPHg and BTEX levels in the remaining monitoring j wells were within historical ranges, and appear to be stable to decreasing. TPHg and BTEX concentration data are summarized in Table 2. Attachment B contains laboratory reports and chain of custody documentation. MTBE was below laboratory method detection limits (MDLs) in wells MW1, MW2, MW5, MW8, MW13B, MW15C and MW1613. MTBE was detected in wells MW3 (52,000 parts per billion - ppb), MW4 (9,200 ppb), MW7 (150 ppb) and MW 14 (57,000 ppb) and MW 16A (1,500 ppb), which are located along the southern portion of the site (Figure 2). In downgradient wells MW 12, MW 15A and MW 15B, MTBE was reported at concentrations of 51 ppb, 9.3 ppb and 400 ppb, respectively. MTBE was also found in well MW9 (4.9 ppb), which is located north of the site. These wells are clearly affected by offsite releases. I�GZA FSIVOL 11DATA1GROUNDZE\ROEK%QMR12004%1gm2004.doc