USGS SET TO DRILL NEXT DEEP MONITORING WELL IN SAN DIEGO

An additional source of water in the San Diego area may come from the San Diego Formation and the overlying, and possibly underlying, sedimentary deposits of sand, silt, and gravel. Prior to the USGS study, which began in 2001, the location, thickness, and water-yielding character of these deposits was poorly known. Since 2001, the USGS has installed 10 deep monitoring well sites throughout the coastal San Diego area; the sites are a key part of creating a three-dimensional view of the San Diego underground. This geologic, water-level, and water-quality information will help guide public agencies and consultants in how to best utilize the limited, mostly brackish, groundwater resources in the coastal San Diego area.

We’ll use mud rotary drilling technique, along with wire-line coring to collect undisturbed samples of sediment from selected depths. The piezometers are mostly 2-inch and one 3-inch PVC pipes which are installed to different depths. Each PVC pipe has 20 feet of perforations at the bottom to allow water to enter the pipe only at that depth. Sand is installed around the perforations and a thick clay-like grout is installed elsewhere. The end result is that we will have a nest of 4-6 PVC pipes that we can measure water levels in, and collect water quality samples from. The 3-inch PVC pipe extends to the bottom of the well bore and allows us to conduct a variety of future measurements, such as identifying changes in salinity throughout the entire 1,500 feet section of aquifer.