Parkway project should curb pollution into lake
January 26, 2009
By J.B. Wogan
Officials hope to avoid a repeat of the algae bloom in 1997. Contributed.
Next month, the mechanical noise of roadwork will bellow along a half-mile strip of East Lake Sammamish Parkway, introducing new pavement and sidewalk.
Normally, that kind of road construction causes extra pollution in runoff, affecting nearby tributaries and lakes.
But the parkway project will actually curb pollution flowing into the lake, according to Sammamish’s Senior Transportation Program Engineer Jeff Brauns. Between erosion control and stormwater filtration, the city plans to spend about $906,350 on controlling pollution going into the lake, Brauns said.
The $8.7 million project will introduce one sand vault as well as a strip of porous concrete sidewalk on the parkway’s east side. Both of those features will filter out potentially harmful pollutants before the water drains into Lake Sammamish.
The project also involves installing bike lanes on both sides of the street and a left-turn lane in portions of the roadway.
A 2006 report, published by a city consultant, indicates that the project would put a significant dent in pollution running into the lake from that segment of the parkway. The report assessed the entire 2.5-mile proposed project, of which only a half-mile has been approved for February.
The total suspended solids going into the lake from the parkway would be reduced by about 95 percent, total phosphorus by 75 percent, total copper by about 66 percent, and total zinc by 78 percent.
The city of Sammamish needs to introduce those mitigation techniques to prevent future phosphorous offloading into Lake Sammamish, according to Kevin Fitzpatrick, regional supervisor for the state Department of Ecology’s water quality program.
“They’re conforming with what we would have required of any other developer along the lake in the watershed right now,” Fitzpatrick said.
There’s a need for better stormwater mitigation techniques, according to Joanna Buehler, president of Save Lake Sammamish.
“Phosphorus is the chief concern at this time,” Buehler said.
Phosphorus feeds into the lakes by way of fertilizers, animal waste and naturally occurring phosphorus in sediment, Buehler said.
It isn’t that phosphorus is bad for the lake in small doses, but if the lake receives too much of it, it can cause explosive algae growth, she explained.
Algae blooms can lead to toxic bacteria and a depletion of oxygen, both of which kill fish, she added.
Data from King County’s lakes monitoring program shows that the lake’s phosphorus levels have not exceeded a water quality goal set in 1996.
A state Department of Ecology assessment in 2008 showed that Lake Sammamish had a water quality problem with its phosphorus content, though it wasn’t so bad — it registered as a Category 2 on a 1-5 scale in one spot in the lake.
Category 5 would warrant a pollution control plan, which Lake Sammamish already has.
Fitzpatrick said Category 2 means that a lake is meeting standards for phosphorus, but it’s at the higher range of those standards.
The issue isn’t current soaring levels of phosphorus, but how to maintain or improve the lake’s current water quality in times of new construction, according to the city’s Senior Stormwater Program Engineer Eric LaFrance.
Based on a standard established by the King County Stormwater Manual in 1998, the city must control 50 percent of phosphorus runoff introduced by new construction, according to LaFrance.
The city will go above and beyond that standard, Brauns said.
“You absolutely have to provide treatment for the area you’re widening, but, pretty much as a policy, everybody goes back. We call it retrofitting,” Brauns said.
What Brauns means by “retrofitting” is that the city will apply the 50 percent standard to the whole half-mile strip, not just the small bit it’s widening for sidewalks and bike lanes.
In terms of pollution, the entire proposed parkway project, spanning 2.5 miles, would introduce one-tenth of an acre of pollution-generating surface area, while it would treat 12.7 acres of new and existing pollution-generating surface area.
That’s why the pollution in runoff would drop off so drastically after the city completes the project.
When the city solicited public input about the project, some residents questioned whether the pollution was so severe that pollution mitigation techniques were necessary.
The same 2008 Department of Ecology assessment that said phosphorus wasn’t awful in the lake said other things were. The lake had alarming amounts of fecal coliform, dissolved oxygen and polychlorinated biphenyl (otherwise known as PCB), which all fell under Category 5.
The mitigation techniques used to limit phosphorous offloading into the lake applies to other types of runoff as well, LaFrance said.
Low levels of dissolved oxygen — which leads to the suffocation of fish in some cases, correlate with higher levels of phosphorus — according to LaFrance. Less phosphorus would mean more dissolved oxygen.
In the case of fecal coliform — probably a combination of dog and cat feces in runoff, bird poop and some human waste — the sand vault would filter a lot of what’s currently going into the lake, LaFrance said.
The project won’t have widespread impacts on the lake’s water quality, but it’s a step in the right direction, according to Sally Abella, King County’s Lake Stewardship Program Manager.
“It’s a good idea to do it,” Abella said.
If the same techniques are applied around the lake, phosphorus levels would drop and the lake would be safer for humans and wildlife, Abella said.
To see the full water quality report, go to the “surface water/water quality” link at www.ci.sammamish.wa.us/ELSP.aspx?Show=Environmental.
Reporter J.B. Wogan can be reached at 392-6434, ext. 247, or jbwogan@isspress.com. To comment on this story, visit www.SammamishReview.com.
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There is a disconnect between the picture of the duck swimming in algae-infested pea soup (admittedly, there is some duckweed in there too) and Sammamish staff’s assertion that “total suspended solids going into the lake from the parkway would be reduced by about 95 percent, total phosphorus by 75 percent, total copper by about 66 percent, and total zinc by 78 percent.” For one thing, the degree of precision in these estimates is dubious. Predictions regarding the project’s performance would be more credible if they were stated as probabilities or ranges of potential effectiveness rather than exact percentages. Secondly, secondly, the project will only work well if it’s built exactly in accordance with designs and specs and impeccably maintained. There is a wealth of literature that shows that stormwater non-point pollution control facilities are not all they’re cracked up to be because of disparities between the design and as-built conditions and/or maintenance shortcomings.