Click on the 1995 image in Guy's link and you will be cheerfully surprised to see that the soccer fields were built on top of the sewage lagoons from the former sewage treatment plant !
The lagoons served as settling ponds prior to further treatment and final discharge to the woods located to the east.
Not to worry though, the lagoons were pumped out and filled with clean fill material and brought up to their current elevations for use as recreation fields.
There was an elaborate spray field system all through the woods that created one of the best deer hunting meccas in New Jersey. The spray fields were cut-in lanes through the woods and the lanes contained lush, waist high grasses throughout the year. It was so lush it drew deer from other states. Not really.
The spray field grid can be seen in the same 1995 image.
I worked on surveying portions of the original plant in the late 1970's and actually waded through the lined lagoons getting bottom elevations for the final plant asbuilts before the system went on line. The lagoons accumulated rain water prior system activation.
The entire treatment system was abandoned several years ago due to excessive nitrate pollution in the groundwater beneath the spray fields.
The plant was then converted to a CCMUA pump station, pumping all of Atco's sewage to beautiful downtown Camden at Ferry Avenue for treatment and discharge to the Delaware River.
The basic tenets of water treatment and groundwater balances were put aside for that move. The Waterford sewage plant and the township that it served is in the Atlantic basin, i.e. all surface runoff ultimately flows to the Atlantic Ocean. The Camden CCMUA plant was designed to accept flows from lands within the Delaware Basin. The issue is that most of Waterford is served by individual shallow wells and septics, allowing water to return to the same acquifers from which it was pumped. Pumping Waterford's public sewage flows to Camden alters the water balance.
Ultimately, the threat to groundwater from the excessive nitrates won the arguments.
Just don't eat the soccer field dirt ! Just kidding.