Drainage system will clean runoff | TahoeDailyTribune.com

Drainage system will clean runoff

Patrick McCartney

A $22 million network of treatment vaults and settlement ponds will clean 95 percent of the runoff from Lake Tahoe’s casino area, according to an assessment of the project released this week.

Most elements of the $21 million system have already been completed, including pretreatment vaults that capture sand, salt and oil, and settlement ponds on Edgewood-Tahoe Golf Course, where the partly treated runoff will be diverted for final treatment.

Still to be completed is a shared export line that will link up existing vaults and drainage facilities on the grounds of the four participating casinos and along Lake Parkway and U.S. Highway 50. Work on the export line, the system’s backbone, may begin this fall.

On Wednesday, the Tahoe Regional Planning Agency’s governing board certified the project’s environmental assessment. Conducted by West Yost Associates, the study concludes that 95 percent of the runoff receiving full treatment will meet TRPA’s discharge requirements for dissolved nitrogen, phosphorus, grease and oil and suspended sediment.

After leaving the ponds, the treated water will flow into Edgewood Creek and then into Lake Tahoe.

The remaining 5 percent of the runoff will be sent through pretreatment vaults, which will remove much of the particulates and grease, although the nutrients, grease and sediments will remain above the TRPA standards. The smaller amount of runoff will be discharged into Golf Course Creek, where it will flow into Lake Tahoe.

However, when all the runoff from the Stateline area is considered together, the system will completely satisfy TRPA’s discharge requirements.

The system was designed to handle peak runoff from the largest 24-hour storm in a decade, and the largest one-hour storm in 20 years.

Built over a period of 10 years, the Stateline Area-Wide Storm Water Facility Plan relies on a catchment system on each property, which feeds runoff into subterranean pretreatment vaults. Export lines then carry the partly-treated water to the settlement ponds.

“In theory, the pretreatment vaults should remove a majority of the pollution,” said Paul Petterson, a senior TRPA planner. “The finer sediments and pollutants are then captured in the treatment ponds.”

The plan calls for monitoring of the system for at least three years, and as long as five years. Maintenance and monitoring will be overseen by the Stateline Storm Water Association, representing the casinos, Douglas County, Nevada Department of Transportation and the Nevada Department of Environmental Protection.

The other large private holding in the plan area, Wells Fargo Bank, will have to decide whether to connect to the larger system or treat its own runoff.

Another environmental benefit of the system is the restoration of 2.7 acres of ponds and wetlands on the golf course.

Jeff Cutler, the assistant director of the League to Save Lake Tahoe, gave a qualified endorsement of the system that will treat 95 or 96 percent of the area’s runoff depending on the amount of runoff.

“We’re 95 to 96 percent pleased,” Cutler quipped. “With the addition of mandatory monitoring and an extra pond, we’re pleased to stand behind the project.”

Tahoe Daily Tribune E-mail: tribune@tahoe.com

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