Gullies caused by erosion at the construction site on Las Virgenes Road on March 4, 2004. Photo: Heal the Bay
Las Virgenes Creek channel inundated with sediment. The area covered by sediment was 22,283 square feet (measured using GPS mapping). Photo: Heal the Bay
Map showing the construction site location on Las Virgenes Road and the extent of the sediment spill in a side channel to Las Virgenes Creek..

On March 4, 2004, dedicated Stream Team member Matt Horns noticed deep gullies in the bare hillside of a construction site beside Las Virgenes Road near the intersection of Lost Hills Road. He investigated and found that recent rain had caused a massive flow of fine sediment into Las Virgenes Creek.

Matt took photos and notes, and Heal the Bay's Stream Team Manger Mark Abramson submitted a report of the spill to Fish and Game and the LA Regional Water Quality Control Board. The builder, Shea Homes, had already received warnings about maintaining their sediment control measures in case of rainfall. Both agencies are taking enforcement actions which will likely result in fines for the builders.

Spill Details
Rainwater flowing down the graded portions of the construction site contributed sediment to Las Virgenes Creek via a side channel. The side channel is fed by a culvert that drains the construction site. From the site, water flows through the culvert, under Las Virgenes Road, and into Las Virgenes Creek behind an office complex (including La Paz restaurant) at 4505 Las Virgenes Road.

The sediment deposit is approximately 300 feet long by 50 feet wide on average and more than 12 inches deep. Debris from the spill was found up to 400 feet downstream of the construction site.

The photos above demonstrate the severity of the sediment spill, and the likelihood the significant riparian habitat and animal life was lost at the spill site. At least one California fish Species of Special Concern, the arroyo chub, lives in this area. Stream Team regularly collects stream insect samples (benthic macroinvertebrates) above and below the spill location.

In addition, Las Virgenes Creek was recently placed on the State 303(d) list as impaired by excess sediment. This sediment spill has increased sediment loading in an already impaired water body.

After discovering the spill, Heal the Bay notified the appropriate agencies and requested they issue an order to cease and desist all grading activities immediately. Heal the Bay also requested that a cleanup and abatement order be issued, and that the builders be required to immediately install all appropriate measures to prevent a further illegal discharge and downstream habitat degradation.