Most of the oilfield operations are invisible from public rights-of-way with the exception of oil pumps and a water evaporation pond along Foxen Canyon Road.

The region has a Mediterranean climate, with cool and rainy winters, and dry summers during which the heat is greatly diminished by prevailing winds from the cold waters of the Pacific Ocean, thirty miles to the west.

Approximately 15 inches (38 cm) of rain falls in a typical winter, with the rainy season lasting from around November to April.

The overall structure of the Zaca field is an anticline, with the oil-bearing units capped by impermeable beds covering them like the gabled roof on a house.

[4] The Monterey Formation in this area dips to the south, and oil migrating updip has pooled against a vertical fault which marks the northeastern boundary of the field.

In these low ranges, oil has difficulty flowing and usually requires assistance from a diluent, steam, water flooding, or another mechanism.

[1] Netherland, Sewell and Associates Inc., an independent resource audit firm, stated their best estimate in their report dated August 23, 2012 Underground Energy's "Zaca Field Extension Project" has 493.2 million barrels of total petroleum initially-in-place on their acreage.

The contaminants driving the risk analysis were polycyclic aromatic hydrocarbons (PAHs) which were produced primarily by internal combustion engines on the site.

During this event, between 800 and 1200 barrels of crude oil, and a larger amount of produced water, escaped from a storage tank through a damaged pump.

Of this amount, an initially estimated 20 barrels of crude oil and 50 gallons of produced water breached the secondary containment berm and entered Zaca Creek.

[12] However, Underground Energy has had a clean environmental compliance record and safety reports since they became the operator of the "Zaca Field Extension Project" in November 2011.

[14] Oil from the field is treated onsite at a small processing facility on the Davis Lease, consisting of heaters, an oil-water separator, and storage tanks.