Based on extensive investigations over many years, site engineers and hydrogeologists know with increasing certainty where groundwater is present beneath the Orrington site, how and where it flows, and the concentrations of mercury which are present. As described in Groundwater Treatment Plant, groundwater is extracted and piped to the GWTP at the Site, where it is treated to remove mercury and other contaminants.
Each quarter, groundwater samples are taken from numerous DEP approved locations on the Orrington Remediation site. This work is performed by Sevee & Maher Engineers, Inc. based in Cumberland, Maine. After analysis at a certified lab, the groundwater quality results are then submitted to the Maine DEP. Previously submitted in the form of a Groundwater Monitoring Report, those results are now submitted, along with other sampling data, in the form of a Short Term Comprehensive Monitoring Plan Data Report.
What is Groundwater?
One of the key aspects of the remediation at the Orrington Site is removing mercury from the groundwater and monitoring this important resource into the future. As previously described under the GWTP article, a state-of-the art groundwater treatment system is in place at the site to extract impacted groundwater, treat it to remove mercury and any other contaminants, and discharge the clean water in accordance with the Maine DEP permit requirements. But what exactly is groundwater?
Water moves in a continuous cycle between the air, ground, plants and animals. The water cycle is generally described as the circulation of the earth's water. Water evaporates from the ocean and surface water (and to a lesser degree from the land) into the atmosphere during warm temperatures; then condenses and falls back to earth as rain or snow during cooler temperatures. The rain or snow flows across the land to lakes and oceans, or percolates beneath the surface of the earth and becomes shallow groundwater. This shallow groundwater eventually makes its way back to the surface through natural flow or from being pumped out, and this surfacing groundwater, as well as the rain and snow that reached the lakes and oceans, all evaporates back into the atmosphere - starting the cycle over all again. The water cycle is also sometimes called the hydrologic cycle.
For groundwater to be available as a water source, it must be able to move through underground materials fast enough to supply useful amounts of water to wells or springs. Water moves through different materials underground at different rates - faster through gravel, slower through sand, and even slower through clay. Groundwater that can be extracted or pumped from below the surface is considered to be in an accessible aquifer.
According to the journal Nature Geoscience, reporting the results of a Canadian-led scientific team, the total amount of groundwater on the planet is estimated to be 6,000,000 million trillion gallons. No, that is not a typo. It means 6,000,000,000,000,000,000 gallons!
It’s important to point out, however, that only an estimated 6% of the total groundwater is in a form that is readily usable by people. The vast majority of the groundwater on earth is very deep underground or in subsurface materials that hold it so tightly it can’t be extracted.
Even where groundwater is accessible, it my contain high salinity, or metals or other chemicals that must be removed before being used for human or agricultural purposes.
These facts and figures quickly lead to an obvious conclusion: management and protection of water resources, including the groundwater we can’t even see, is important for the future. The site investigations to date, ongoing monitoring results and a groundwater model will all be used to design the final treatment system and the long-term monitoring program for the Site.