Indicators groundwater monitoring

Thomas, D.B. and Delfino, J.J. A gas chromatographic/chemical indicator approach to assessing gronnd water contamination by petroleum prodncts. Groundwater Monitor. Rev., 11(4) 90-100, 1991. 

Activity levels for selected radionuclides In groundwater measured during 1981 (DOE-RL 1990 and DOE-RL 1991) show the contamination patterns that had developed by that time In the vicinity of the 116-N-l crib and trench (Table 5-10). The tritium data Indicate high levels of contamination In the entire area covered by the then-existing monitoring network. These data also demonstrate that the Impact of the 116-N-l crib and trench extended In all directions. The full extent of Influence of the 116-N-l facility at this time, particularly In the southern and eastern directions, cannot be determined because the network of groundwater monitoring wells Is limited. 

The solubility of methyl parathion is not sufficient to pose a problem in runoff water as determined by an empirical model of Wauchope and Leonard (1980). Some recent monitoring data, however, indicate that methyl parathion has been detected in surface waters (Senseman et al. 1997). In a study to determine the residue levels of pesticides in shallow groundwater of the United States, water samples from 1,012 wells and 22 springs were analyzed for methyl parathion. No methyl parathion was detected in any of the water samples (Kolpin et al. 1998). In a study of water from near-surface aquifers in the Midwest, no methyl parathion was detected in any of the water samples from 94 wells that were analyzed for pesticide levels (Kolpin et al. 1995). Leaching to groundwater does not appear to be a significant fate process. 

Groundwater samples collected over the last 10 years from monitoring and private water wells in the offpost area of RMA have provided data regarding the extent of diisopropyl methylphosphonate. The data indicate that diisopropyl methylphosphonate in the alluvial aquifer extends from the RMA northwest to the South Platte River. In the 1995 sampling event, diisopropyl methylphosphonate concentrations ranged from less than 0.392 g/L, the detection limit, to just over 600 g/L in this area. The highest reported concentrations were present upstream of the Peoria Street Treatment Plant. The lowest or non-... 

Regarding POCs, eight compounds (see Table 1) were selected as indicators from the qualitative analysis of leachate due to their frequent detection, to their abundance, and to their absence in groundwater wells monitored upstream the landfill. The selected compounds include plasticizers or their degradation products, insect repellent and natural compounds resulting from anthropogenic pollution. 

In the lower fan areas Se concentrations were monitored up to 400 pg/L. Similar historical distribution of soil Se content and shallow groundwater content indicate that dissolved selenium species were leached from saline soils by irrigation water. The drainage discharge of shallow groundwater and subsurface irrigation water was accompanied by increasing accumulation of Se in Kesterson Reservoir. 

Implement a tank water bottom monitoring system and maintain a schedule that includes a log or other record that will identify or indicate releases of crude oil or its fractions before reaching the groundwater and/or... 

Flask tests involve the testing of native soil and groundwater without additives, in which the oxygen uptake (or carbon dioxide produced) is continually monitored. After about 1 to 5 days, the concentration of contaminant is analyzed and compared with the initial concentration. Results indicate the rate of degradation with only oxygen addition, and the quantity of oxygen required per unit of contaminant. 

Monitoring remedial progress requires monitoring of both groundwater and aquifer media samples for compounds of concern and other indicator parameters. Typically, groundwater samples should be collected and analyzed monthly, or quarterly at a minimum. More frequent sampling is not usually justified because groundwater flow is relatively slow and biochemical reactions in the subsurface are typically slow compared with laboratory reactions. Confirmatory soil samples are routinely collected, prior to site closure, to demonstrate that cleanup objectives have been achieved. 

Exposure Levels in Environmental Media. Data are available on the occurrence of hexachlorobutadiene in air, water, and foodstuff. The majority of the monitoring data on hexachlorobutadiene are outdated and therefore more recent information on the levels typically found in the environment would allow for more accurate estimation of human exposures, and could also serve to indicate time- dependent trends when compared with older data. No data were located regarding the occurrence of hexachlorobutadiene in groundwater or soil. 

Again, the absence of monitoring data does not necessarily indicate a lack of cresols in the environment. Cresols are widely occurring natural and anthropogenic products. However, biodegradation is probably the dominant mechanism responsible for the rapid removal of cresols from surface waters (see Section 5.3.2.2). Nevertheless, cresols may persist in extremely oligotrophic waters, in waters with limited microbial communities, and/or under anaerobic conditions such as in some sediments and groundwater aquifers. 

As part of EPA s National Runoff Program in Fresno, California, the soil water and groundwater at depths 26 m beneath five urban runoff retention/recharge basins were monitored during a 2-year study (Nightingale 1987). The results indicated that there were no significant downward movements of nickel with the recharge water. 

Elevated tin levels have been detected in both surface and groundwater at hazardous waste sites. Data from the Contract Laboratory Program (CLP) Statistical Database indicate tin occurred at about 21 % of the sites sampled at a geometric mean concentration of about 50 jog/L (CLPSD 1989). The CLP database includes data from both NPL and non-NPL sites. These values may be underestimates, since monitoring for tin was discontinued before 1986. 

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