With the ski season winding down, sun and warmer temps mean more recreational opportunities in Tahoe. But along with that is the potential for damage to the beauty and clarity of Lake Tahoe with all the runoff, particularly from South Lake Tahoe parking lots. Heavenly is doing it’s best to mitigate nonpoint source pollution in the Tahoe Basin by installing a StormFilter treatment system. “These units, when fully operational, are designed to remove a broad range of stormwater pollutants including oil and grease, sediment, soluble metals, organic materials, and certain nutrients,” says Michelle Gamble, P.E., Resource Concepts Inc.

While the spring skiing rages on into May, massive amounts of snow melt will be sheeting off the mountain. To mitigate damage to the clarity of Lake Tahoe, four large filtration vaults under the parking lot will purify runoff from the 15 acre facility. “The goal is to meet stormwater discharge standards,” Michelle says, “which are really stringent.”

The filtration is accomplished by 428 ZPG filter cartridges which strain out sediment, chemicals that can pollute the downstream flow of Bijou Creek and damage the clarity of Lake Tahoe. These filters use zeolite, perlite, and granular activated carbon to remove Nitrogen, phosphorous, suspended and dissolved solids turbidity and sediment from the parking lot runoff.

The System is designed to handle a 20-year 1-hour storm event as required by the Tahoe Regional Planning agency and the Lahontan Regional Water Quality Control Board. The system can handle a 15 cubic foot per second flow, or the equivalent of 1 inch per hour. Any excess flows will be diverted around the system. Michelle says that most of the particulate and contaminates will be washed into the filter initially so excess flows will be clean.

“We’re naturally filtering Edgewood Creek of sediment,” says Russ Pecoraro, Heavenly’s Director of Communications. That is accomplished with a constructed wetland on the Nevada side base area. “As technology catches up with science we’ll be able to keep up and keep fighting the good fight.” Heavenly is also reinforcing the site with slope stabilization and other best management practices that reduce erosion and keep sediment out of the creek.

While you’re scratching out your last turns @ Heavenly this system will be delivering clean water to the lake for summer fun. The purity of that water will be monitored above and below our new system to ensure that the Total Maximum Daily Load (TMDL) for suspended sediment on Heavenly Valley Creek is not exceeded. This is one of the largest systems of it’s kind in the world and uses the most advanced filtration technology available today.

The site posed some challenges initially with it’s steep grade and large area of impervious surface. Also since the water table is very close to the ground surface, storm water infiltration is slow. With all the cars and sand, “it can be a pretty nasty site in the winter,” Michelle says.

The way the system works is amazing. Each filter sits on a hole in the bottom of the vault which leads to the discharge duct. Runoff from the lot enters the vault and fills it up until water pressure activates a siphon effect within the cartridges. Water enters the filter media from the bottom and is drawn up to the top where clean water drains through a tube and out through the floor. The filters cost $250 to replace and can last up to seven years.
“Heavenly is putting forth a huge effort for this site,” Michelle says.

See more pictures here and video here. Check here for other improvements in store for Heavenly next season.

Got any questions? Fire away!

This entry was posted on Monday, April 14th, 2008 at 2:53 pm and is filed under On The Mountain. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.