Chilkat Valley News - Serving Haines and Klukwan, Alaska since 1966

Fort Seward bioswale aims to trap, filter dirty snow

 


At the southwest corner of the Fort Seward parade grounds, work started Monday on two crescent-shaped “bioswales,” subterranean catchments aimed at preventing pollutants in plowed snow from entering Portage Cove.

Takshanuk Watershed Council executive director Meredith Pochardt watched Monday as a Haines Borough crew filled a three-foot-deep trench with three-inch rocks. Wrapped in a geotextile fabric, the rocks are intended to capture sediments, road grease and salt in an area where loads of snow are dumped.

Vegetation planted in earth above the buried rocks will help process the contaminants, Pochardt said.

“The goal is to collect melt-water and treat it and let the pollutants be settled out into the drain rock before the water reaches Portage Cove,” Pochardt said.

A second bioswale of identical dimension – about 70 feet long and 10 feet wide – was to be dug Tuesday on the parade grounds’ southeast corner.

Plowed snow accumulates many contaminants, Pochardt said. “Tests of snowbanks in Juneau showed they were really toxic, so this has been elevated as an issue of concern” for the state Department of Environmental Conservation, she said.

Pochardt said the watershed council worked with the borough in making changes to the town’s snowplow plan so snow wouldn’t be deposited directly into Portage Cove, a longtime practice. “We want to put snow where it can be treated,” she said.

Snow previously dumped off the edge of the cruise ship dock will instead go onto a lot adjacent to the public safety building, said Brad Ryan, the borough’s public facilities director.

“We haven’t had a big snow year to know if it’s going to work practically, but we hope it does,” Ryan said.

Besides trapping pollutants, bioswales hold water and release it slowly, unlike pavement, which creates a type of flash flooding, Ryan said. Water slowly migrates for a more consistent flow, recharging aquifers during low-flow periods, he said.

The watershed council recently built a smaller bioswale on a snow dump on the group’s property near Sixth Avenue and Dalton Street.By Tom Morphet

At the southwest corner of the Fort Seward parade grounds, work started Monday on two crescent-shaped “bioswales,” subterranean catchments aimed at preventing pollutants in plowed snow from entering Portage Cove.

Takshanuk Watershed Council executive director Meredith Pochardt watched Monday as a Haines Borough crew filled a three-foot-deep trench with three-inch rocks. Wrapped in a geotextile fabric, the rocks are intended to capture sediments, road grease and salt in an area where loads of snow are dumped.

Vegetation planted in earth above the buried rocks will help process the contaminants, Pochardt said.

“The goal is to collect melt-water and treat it and let the pollutants be settled out into the drain rock before the water reaches Portage Cove,” Pochardt said.

A second bioswale of identical dimension – about 70 feet long and 10 feet wide – was to be dug Tuesday on the parade grounds’ southeast corner.

Plowed snow accumulates many contaminants, Pochardt said. “Tests of snowbanks in Juneau showed they were really toxic, so this has been elevated as an issue of concern” for the state Department of Environmental Conservation, she said.

Pochardt said the watershed council worked with the borough in making changes to the town’s snowplow plan so snow wouldn’t be deposited directly into Portage Cove, a longtime practice. “We want to put snow where it can be treated,” she said.

Snow previously dumped off the edge of the cruise ship dock will instead go onto a lot adjacent to the public safety building, said Brad Ryan, the borough’s public facilities director.

“We haven’t had a big snow year to know if it’s going to work practically, but we hope it does,” Ryan said.

Besides trapping pollutants, bioswales hold water and release it slowly, unlike pavement, which creates a type of flash flooding, Ryan said. Water slowly migrates for a more consistent flow, recharging aquifers during low-flow periods, he said.

The watershed council recently built a smaller bioswale on a snow dump on the group’s property near Sixth Avenue and Dalton Street.

About $10,000 for the Fort Seward projects was secured from the Alaska Clean Water Actions program, Pochardt said.

Pochardt was asked how contaminated snow compared to Portage Cove contamination from the town’s sewer outfall line, which takes screened and separated sewage from the borough’s treatment plant on Fair Drive and deposits it at a spot outside downtown’s harbor breakwater.

“The sewage is a bigger issue. It’s not that that’s okay, but this is an issue we can easily tackle, so why not? It’s relatively easy to treat. It’s low-hanging fruit,” Pochardt said. “These types of projects have been funded because they work and they’re easy to implement.”

The Fort bioswales will be identifiable as a slight surface depression and by wetlands vegetation specially chosen to tolerate both very wet and dry conditions. The vegetation is intended to capture the runoff and “treat” it through uptake and root action, she said.

Bioswales aren’t new to Haines. They were established along Fair Drive more than 20 years ago, to keep road contaminants out of Sawmill Creek. Fuel distributor Delta Western constructed “a super sophisticated” one to trap petroleum compounds around a historic gas station at the intersection of Main Street and Old Haines Highway.

“That one’s much more complex than what we have here, but it’s the same concept,” Pochardt said.

In related news, Takshanuk will be working on a sediment-retention wetland through a separate, $14,000 grant. The goal of that project is to collect sediment-laden water from a creek near Union and Dalton streets. “That creek drops a lot of sediment into Sawmill Creek,” Pochardt said.

About $10,000 for the Fort Seward projects was secured from the Alaska Clean Water Actions program, Pochardt said.

Pochardt was asked how contaminated snow compared to Portage Cove contamination from the town’s sewer outfall line, which takes screened and separated sewage from the borough’s treatment plant on Fair Drive and deposits it at a spot outside downtown’s harbor breakwater.

“The sewage is a bigger issue. It’s not that that’s okay, but this is an issue we can easily tackle, so why not? It’s relatively easy to treat. It’s low-hanging fruit,” Pochardt said. “These types of projects have been funded because they work and they’re easy to implement.”

The Fort bioswales will be identifiable as a slight surface depression and by wetlands vegetation specially chosen to tolerate both very wet and dry conditions. The vegetation is intended to capture the runoff and “treat” it through uptake and root action, she said.

Bioswales aren’t new to Haines. They were established along Fair Drive more than 20 years ago, to keep road contaminants out of Sawmill Creek. Fuel distributor Delta Western constructed “a super sophisticated” one to trap petroleum compounds around a historic gas station at the intersection of Main Street and Old Haines Highway.

“That one’s much more complex than what we have here, but it’s the same concept,” Pochardt said.

In related news, Takshanuk will be working on a sediment-retention wetland through a separate, $14,000 grant. The goal of that project is to collect sediment-laden water from a creek near Union and Dalton streets. “That creek drops a lot of sediment into Sawmill Creek,” Pochardt said.

 
 

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