Plains All American must install a range of safety features on the oil pipelines that soiled a California beach before a restart, a U.S. regulator said.

In an 11-page order, the federal Pipeline and Hazardous Materials Safety Administration found operating Line 901 and 903 in Santa Barbara, Calif., "would be hazardous to life, property, or the environment" without corrective actions taken by the company.

A rupture last year on the pipeline system resulted in the release of around 3,000 barrels of oil on Refugio State Beach and along the California coast. In May 2015, the PHMSA completed its investigation into the incident and identified external corrosion of pipeline walls as the direct cause of the failure. May of the indirect causes, the agency said, were preventable.

An amended corrective action order from the PHMSA contains five pages of steps the company must take in order to restart the system. Steps range from a "basic level" of leak detection in pipeline operator control rooms to the "appropriate" use of tools to assess corrosion.

The amendment "requires the operator to implement advanced leak detection capabilities, install additional safety valves and pressure sensors, develop a long-term plan for corrosion prevention, and update its facility response plan for both pipelines before they are allowed to restart," the PHMSA stated.

Plains issued no comment to the amended PHMSA order. After the initial order from May 19, the company said it would stand mute because investigations and pending litigation were ongoing.

The California and Santa Barbara county attorneys general filed criminal charges in May against Plains and one of its employees, 41-year-old James Buchanan, for the release. The penalties could amount to $2.8 million for Plains.

Plains said it was "deeply disappointed" with the decision to pursue criminal charges.