What's Up with That? Barren area on Burnt Bridge greenway in transition
Wednesday, June 15, 2011
During a recent walk along the Burnt Bridge Creek Trail, near the 92nd Avenue end, we noticed a grassy slope was completely dead from herbicide use. Isn’t the point of the greenway to keep harmful pollutants from entering the water there? How’s the water in BBC, anyway? And I’ve noticed a greenhouse on the trail near Andresen Road. Who’s growing what in there and why?
— a blend of questioners and questions
The slope you’re referring to is a “transition area” in between the trail and a wetland, according to greenway/sensitive lands supervisor Tim Esary.
Esary’s Greenway/Sensitive Lands Team “has had to closely mow a large swath of this area to keep it under control, which is costly, time consuming and not the optimum environmental technique, either,” he wrote in an email.
So, to minimize both mowing and erosion, Esary said, the greenway team decided to replant the area with native plants only. They started by using a “fish-friendly spray” called Aqua Master to remove the invasive vegetation. Aqua Master “has been shown not to move through soils,” Esary said. “We are approved to use this spray in transition areas for weed infestations and other needs, but do so very carefully, following all directions to the letter.”
Esary said his team mostly sticks with nonchemical means of controlling pests “but can also use approved and carefully applied chemical treatments,” depending on the specifics of the situation — for example its size, level of infestation and the type and maturity of the weed.
And how’s the water? According to a draft quality assurance plan developed by the city, Burnt Bridge Creek’s temperature and levels of fecal coliform, dissolved oxygen, nitrates and pH all exceed state standards. The detailed plan includes the city’s new targets for water quality monitoring and improvement, and can be viewed at http://www.cityofvancouver.us/waterallaround.
Loretta Callahan, the city’s public works spokeswoman, pointed out that “nonpoint source pollution” is a leading cause of water quality problems across the nation. That means stuff that runs into water not from giant factory pipes or mammoth waste dumps but from small, diffuse sources: residential and agricultural fertilizers, herbicides and insecticides; oil and grease from city streets; erosion from stream banks; bacteria and nutrients from livestock; leaking septic systems and pet waste, for example. Callahan said water quality monitoring reveals spikes in pollutants running into county streams in spring and fall, when people are applying the most chemicals to their lawns.
“The temporary greenhouse structure you’ve asked about is a good example of what the Greenway/Sensitive Lands Team is doing ... by propagating native plants for restoration in a very cost-effective way,” she said
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