PNEUMATIC SLUG TESTING – AN EFFECTIVE METHOD FOR HYDRAULIC CONDUCTIVITY ACQUISITION FOR HAZARDOUS WASTE SITES

Aquifer characterization at hazardous waste sites is complicated by the growing need to reduce contaminant exposure to site workers. Aquifer pumps tests at hazardous waste sites are generally complicated to plan and expensive to carry out. Smaller scale aquifer tests, such as slug testing, is an effective method to acquire hydraulic conductivity (K) as the tests are less expensive, less complicated, and generate less investigation derived waste. Slug tests are also shorter in duration, several can be performed simultaneously, and can effectively identify heterogeneities with one, or several aquifers.

Conventional slug tests generally utilize a PVC slug or bailer to displace the static water level in the well. PVC slugs are often filled with sand to add weight and are usually not water tight, nor can they be effectively decontaminated. Bailers are an effective method for displacing the static water level because they are inexpensive, allowing for each tested well to have a dedicated bailer, which can be disposed of once the testing has been completed. However, both PVC slugs and bailers bring contamination to the surface where workers can be exposed. Bailers additionally generate IDW that must be properly disposed of.

Pneumatic slug testing is an effective method because it eliminates a physical slug, such as the PVC slug or bailer, and is relatively inexpensive and simple to construct. The data generated during pneumatic slug testing generally contains less noise as there is no physical slug to disturb the pressure transducer or leakage to skew water level response. The pneumatic slug testing apparatus is generally constructed of PVC and consists of an air tight pressure transducer feed through a fitting, a stem valve to allow a bike pump to introduce the pneumatic slug, a low pressure gauge to monitor the aquifer’s response to the added slug and for potential air leaks, and a ball valve to release the pneumatic slug from the system. Pneumatic slug testing can be a viable alternative for slug testing at hazardous waste sites as it reduces exposure of groundwater contaminants to workers and eliminates IDW generation. Additionally, the pneumatic slug testing apparatus seals the well head eliminating exposure of volatile contaminants during the test.