Groundwater investigations come in all shapes and sizes, often as part of a comprehensive site assessment. In Oregon, groundwater sample analytical results are often compared with Oregon Department of Environmental Quality’s Risk Based Concentrations (RBCs) for various exposure pathways to groundwater, in order to decide whether the groundwater is “clean enough”.
The simplest groundwater assessment, a grab sample of water from a pit, may not accurately represent groundwater conditions, as it is likely a worst case scenario. However, a grab sample is an inexpensive starting point to help decide if groundwater is “clean enough”.
Push probe rigs are often used to collect groundwater samples. Push probes are used when only one round of groundwater samples is needed. A temporary boring is drilled, the groundwater sample is collected, and the boring is then sealed.
For sites where groundwater concentrations are documented over a period of time, three or more monitoring wells are installed. Groundwater sampling typically occurs once every quarter for at least a year. Groundwater sampling is discontinued, with DEQ concurrence, after four quarters of sampling have shown that the groundwater cleanup goals have been met.
Sprecher Group has conducted numerous groundwater investigations. Representative projects include:
- Pentachlorophenol/petroleum release to soils, and potentially to shallow groundwater, at a ranch in eastern Oregon. Impacted soil had previously been removed. SG conducted a push probe groundwater investigation, evaluated the analytical results using DEQ’s RBC protocols, and prepared a final report. Findings indicated that risk to human health from groundwater was not likely present. DEQ has issued a No Further Action letter for this site.
- Active Service Station, Klamath Falls, Oregon. Initial petroleum release in the 1990s to shallow groundwater. In 2009, SG reviewed site work to date, then conducted additional soil and groundwater sampling and data evaluation. SG collected semi-annual monitoring well samples and prepared associated sampling reports, for DEQ submittal, from 2009 to 2016. DEQ has issued an NFA letter for this site.
- Industrial Site, Klamath Falls, Oregon. Historic nitrate/salt release. Conducted a technical review of existing site data and reports in 2005. Oversaw several rounds of additional monitoring well installation and sampling since 2005. SG currently collaborates with facility staff during quarterly groundwater sampling and prepares quarterly sampling reports for submittal to DEQ.