Q: If you infiltrate stormwater over a long period of time, won't the soil become contaminated?

A: It is true that stormwater does contain contaminants. That is one of the reasons we want to reduce the direct discharge of stormwater into streams. The infiltration of stormwater is effective in reducing contaminants for several reasons. One reason is that soil acts as a natural filter because many contaminants "stick" to the sediments carried along with stormwater. The sediments that carry the contaminants are trapped in an infiltration BMP.

BMPs must be sited and selected very carefully. Obviously, a heavily contaminated site would not be an ideal location for an infiltration BMP. In some cases, a pretreatment system can be used in conjunction with an infiltration BMP.

At our particular site, we found that after 100 years of infiltration the soil under the infiltration pits would still be considered clean fill according to PADEP standards.

Q: Could the pits have originally been cesspools?

A: 1928 records show the existing sewer lines of the two buildings do not connect or even go near the pits. So, the idea that the pits were originally designed as septic tanks was ruled out. There was also a line from the buildings for grease from the Monastery kitchen, but did not travel to or near the pits. Thus, the pits could only have one function: rain water storage and infiltration.

Q: How did you determine the copper concentrations?

A: The particular method used for extraction and testing was the DTPA extraction method described in the “Recommended Chemical Soil Test Procedures for the North Central Region” by the Missouri Agricultural Experiment Station.