Berms and treatment ponds for snow disposal sites
Runoff from snow dumped next winter will be treated for any harmful chemicals as the city rebuilds the Mendenhall Valley snow disposal site.
The project got the green light this week from the Juneau Planning Commission.
Under a Conditional Use Permit, the snow site, which grows to 40 feet some winters, will be set back and developed.
CBJ Engineer Michelle Elfers is project manager. She says soil will be excavated and drainage rock added then graded into what’s called a V-Swale design.
“The pad is graded into a V in the center so the water as it melts from the pile will go into the center of the pad then drain down and some of the water will be able to filter through the rock and that in itself is water treatment,” Elfer says. “Then the water that continues to run through the swale will go into a detention pond and what that does is dilutes the water.”
After a study of several sites around the borough, the Mendenhall Glacier bus parking lot off Glacier Spur Road is still the best for disposing snow cleared from Juneau roads, according to the CBJ streets department. It has dumped snow there since 2006.
The city has been working with the U.S. Forest Service on the plan, with the Forest Service conducting an Environmental Assessment. It is expected to soon grant a five-year special land use permit for snow disposal.
The area off Glacier Spur Road is a parking lot for tourist buses in the summer.
The Gastineau Aeromodeler’s Society also has an agreement with the Forest Service to fly model airplanes from the parking lot summer and winter.
The Conditional Use Permit provides for a 10-foot construction setback and a 25-foot snow storage setback from the model plane runway.
Construction on the snow disposal area will be done this fall.
The city plans to develop another site off Thane Road near the Rock Dump. Elfers says it too will have berms, a rock pad and treatment pond.