Why Groundwater Matters

Where does groundwater come from?

Rain, sleet or snow that soaks into the ground. Gravity pulls the water through soil, sand, gravel or rock until it reaches an area where the ground is filled with water. The top of this area is called a water table. The water table can be near the surface soil or hundreds of feet below.

How did the groundwater at the Petro-Chem site become contaminated?

Over the years, many incidents contributed to the overall pollution of the plant -- building fires, leaking drums, a diesel fuel spill, an old hazardous waste burn pit. Over time, rain water and water used to fight the fires at the plant soaked the contaminants deep into the ground.

Can groundwater be cleaned?

Yes, but it is time consuming and costly.

What is being done with the groundwater at the Petro-Chem site?

A groundwater extraction system keeps the contaminated groundwater from moving into nearby creeks and wells.

How does the system work?

An extraction trench and four extraction wells are placed underground in known contaminated areas. As the water moves into the trench and wells, it is pumped into an oil separator. The oil is removed, drummed and sent off site for disposal. The water is then sent through a sand filter which removes small particles and then moves to an equilibrium tank. The water is run through two 1-ton carbon filters, which strip out organic compounds. The cleaned water is sent to Rock Hill's sewer system, where it is treated further.

How does DHEC know the system is working?

Monitoring wells are located outside of the wells and trenches of the groundwater extraction system. The water in these wells is routinely tested for contaminants. DHEC says the water has consistently shown no evidence of pollutants -- indicating that the system is containing pollutants to the operations area.

This story was originally published September 14, 2008 at 12:14 AM with the headline "Why Groundwater Matters."