Water quality officials have filed a complaint seeking a $5.5 million fine from Caltrans and a Santa Rosa contractor for allowing soil to be washed into Copeland Creek during work to widen Highway 101.

It is the largest fine that the North Coast Regional Water Quality Board staff has ever recommended, said Luis Rivera, assistant executive officer. If the two parties contest the fine, a hearing will be held before the water board Jan. 24, Rivera said.

The violation occurred during a June rainstorm that overwhelmed the efforts of the Ghilotti Construction Co. to divert water around a culvert project.

It resulted in 150 cubic yards of soil being washed into Copeland Creek and into the Laguna de Santa Rosa, according to the complaint.

"The reason we are bringing the complaint is there were large impacts to a receiving waterway that is already impacted by sediment, the Laguna de Santa Rosa," Rivera said.

The laguna is part of the Russian River watershed and the sediment is a threat to the spawning areas of Coho salmon, which are on the endangered list, and chinook salmon and steelhead, which are listed as threatened.

The complaint was issued Monday. It alleges that best practices for erosion control and storm runoff were not used, and Caltrans did not file monthly reports on the project.

It asks for a fine of $5,565,860, which includes $25,000 cost of the investigation by the water board. The maximum fines that could have been levied were $167 million, according to the complaint.

Ghilotti was extending a culvert to accommodate the widening of Highway 101 between the Rohnert Park Expressway and Pepper Road when the incident occurred.

According to the complaints, the contractor was using two 18-inch pipes to divert Copeland Creek around the culvert, despite warnings from water board inspectors that they may not handle runoff from a summer storm. A four-foot pipe was recommended instead.

When a storm hit on June 28, the water diversion efforts failed and water board inspectors said that three pumps were installed to pump water around the work area, which caused turbidity downstream, according to the report.

The contractor also built two earthen dams and used bags filled with sand silt, rather than washed gravel, the complaint said.

Neither Caltrans nor Ghilotti commented on the complaint.

You can reach Staff Writer Bob Norberg at 521-5206 or bob.norberg@pressdemocrat.com.