In 1982 a seep containment device was placed on the sea floor 1.5 km east of oil platform Holly in a joint effort by ARCO and Mobil oil companies. This device comprises two steel pyramids or tents measuring 100 by 100 feet each that capture emissions from numerous hydrocarbon seeps on the sea floor [Rintoul, 1982]. Captured gas is sent ashore through a sea floor pipeline for commercial sale and oil is periodically removed at the tents. The gas capture rate in 1982 was 4.2 x 10^4 m 3/day (1.5 x 10^6 ft3/day). Rates started declining in 1989 and were down to 1.9 x 10^4 m3/day (0.65 x 10^6 ft3/day) by late 1994. Over the life of the South Ellwood field over 50 million barrels of oil have been produced. Accompanying this has been a decrease in reservoir pressure of about 40%. This pressure reduction is proposed as the cause of the drop in capture rate at the Seep Tents.
Rintoul, W., ARCO caps Santa Barbara Channel Seep, Pacific Oil World, 75, 6-9, 1982.