Site Investigation and Preliminary Assessment of the Colorado River Seep Site in Wharton County, Texas (RRC CU# 03-51041)

The University of Texas at Austin, Bureau of Economic Geology (BEG), investigated the Colorado River Seep site near the border of Wharton and Matagorda Counties for the Railroad Commission of Texas (RRC) in July and August 1999. The area of concern occupies 0.03 mi2 (0.07 km2) on the H. C. Cockburn lease adjacent to the east bank of the Colorado River. The RRC and Magnet-Withers field operators have attempted to identify possible sources of the crude-oil seep since 1992; however, there have been no conclusive findings. The objectives of this study were to (1) characterize the extent of hydrocarbon impacts, (2) determine whether further work is needed to eliminate possible hydrocarbon sources, and (3) produce a summary report containing results of the field investigation. The scope of work consisted of collecting continuous cores and installing groundwater monitoring wells in 12 boreholes, located as to assess each of several possible sources of the crude oil: • a plugged and abandoned oil well, • two tank batteries, and • as many as four former surface pits that are reported to have been used for oil storage, salt-water storage, or drilling-mud containment. Data from both this and previous studies indicate that crude oil impacts several locations within the study area, but not all of them are related to the currently observed crude-oil seep.