Stormwater June 2012 : Page 18
Fine-Tuning Street Cleaning Managers are detecting an increasingly positive effect on pollutant levels. BY DON TALEND S an Angelo, TX, home of the Concho River that flows through the downtown area and three lakes, is a lot like many cities that sprang up along the banks of a river. Stormwater runoff affects the viability of drinking water and the ecosystem not only of San Angelo, but also of several com-munities located downstream. The Texas Commission on Environmental Quality (TCEQ) lists the North Con-cho River on its 2010 303(d) list for a water-quality impairment and cites water-quality concerns for high levels of bacteria and depressed dissolved oxygen (DO). As part of its stormwater quality permit issued in August 2007, the city was required to submit a Na-tional Pollutant Discharge Elimination System (NPDES) Phase II stormwater management program by February 2008, with full implementation by August 2012. Cities such as San Angelo are fi nding that cleaning streets of oils, grit, trash, and other pollutants is a much more cost-effective way of keeping these materials out of stormwater before it reaches rivers, lakes, and streams than is cleaning out storm drains and catch basins on a regular basis. San Angelo, population 93,200, has about 1,100 curb miles of streets and more than 70,000 feet of city-owned open storm drains. The city’s acquisi-tion of fi ve Tymco Model 600 regen-erative air sweepers from August 2010 through December 2011 has been a major part of its initiative to get the river off of the list of impaired water bodies by creating a cleaner stormwa-ter environment before runoff enters these structures instead of cleaning large quantities of pollutants from the structures periodically. Although bac-teria and DO levels are not directly affected by street sweeping, they are indirectly connected because the de-bris and pollutants picked up by street sweepers contain elements such as dead vegetation that grow bacteria and other organisms that use up much of the oxygen in the river. The city is divided into six districts, each of which is cleaned several times a year—except for both sides of the river in the downtown area, which is cleaned every morning before traffi c picks up. “It’s an aesthetic issue, but also, street sweepers pick up a lot of material off of the street,” says Clinton Bailey, city en-gineer. He adds that clean streets make the downtown area more of a potential tourist attraction, so the city purchased a smaller Tymco 600 sweeper that is dedicated to this area. Street cleaning is not a new concept to the city; prior to 2010, three sweeper-type machines were in use. “With regenerative [sweepers], you have a vacuum system,” says Doug Kirkham, the city’s stormwater superintendent. “With the regular broom system, we were fi nding that we were sweeping and doing some good, but we were not able to vacuum up the small particles that are embedded into the streets. We found that we were stirring up the dirt and getting some of it, but a lot of it was turning into dust particles and spreading into the air.” Kirkham esti-mates that, prior to the purchase of the Tymco regenerative air sweepers, the city was picking up 200 to 250 tons of pollutants from the streets per month. Since the purchases, the city has begun tracking the total weight of pollutants and is now picking up 400 to 450 tons per month. Art Gonzales, stormwater inspec-tor for the city, reports that the new machines are making a difference in terms of effectiveness. “I think they do a really good job of picking up small-er particles,” he says. One option that the operator relies on is the machine’s Broom Assist Head, which loosens dirt before removing it from the surface by using an extra broom installed within the sweeper head that works in con-junction with a blast of air from the blast orifi ce. When necessary, opera-tors also use the gutter brooms to loos-en fi ne dirt particles that get packed down in the curb line, Gonzalez adds. When the stormwater management plan was implemented, the city cleaned out the storm drains and made neces-sary repairs. Then the street cleaning program was implemented. “We’ve gone back in and looked at these storm drains and it’s amazing, the difference from what they were to what they are now,” says Kirkham, noting that no regular maintenance was performed on the storm drains before the stormwater management plan was implemented. “I can’t give all of the credit to the sweep-ers because some of those storm drains have probably been in the ground for 40 years and there has never been any maintenance on them. Now we’ve gone in and cleaned them out, and we’re fi nding that they’re staying clean. We’re keeping the debris off of the streets, and then when we are blessed with the rain, the storm drains are fl owing; we don’t have debris caught in them.” Kirkham reports that the public does not seem to mind the fact that the street sweepers occasionally clean the pavement. “The response is excellent, I would say. People appreciate the ser-vice. We added a stormwater manage-ment fee to the water bill, so we have to be out there in the public eye and let them see what we’re doing.” Currently, however, the cleaning schedule is not determined far enough in advance that residents can be given notice to move their vehicles. Besides picking up signifi cantly greater quantities of pollutants so that 18 June 2012 www.stormh2o.com
Fine-Tuning Street Cleaning
Don Talend
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