The Southeast Michigan Council of Governments (SEMCOG) recently held a series of seminars entitled "Municipal Operations for Clean Water: Streets and Parking Lots."
Angela E. Riess, planner for SEMCOG, told attendees that storm sewer catch basins should be cleaned on an annual basis.
Catch basins are included in storm sewer system designs in order to remove solids such as gravel, sand, oils, and organic material carried by storm water. Catch basins also contain elevated concentrations of metals (attached to solids) from street runoff or drainage from industrial, commercial and residential properties. In order to maintain the storm sewer systems' effectiveness, catch basins must be periodically cleaned out.
The Michigan Department of Environmental Quality (DEQ) Water Bureau (WB) and Waste and Hazardous Materials Division (WHMD) oversee environmental regulations pertaining to this activity.
"It's highly recommended that catch basins be cleaned annually. What we're really concerned about is the performance of that catch basin," Riess said. She pointed out that if, for example, there is a construction project going in a particular area, then the catch basins in that area should be put on a priority schedule.
"If you're using a sewer cleaning truck to clean your catch basins, that sediment that you collect is classified as liquid industrial waste. So what that means is if you are using a sewer cleaning truck to clean out all of the liquid and solid, you can discharge that material to a wastewater treatment plant, with prior approval from the wastewater treatment plant operator," Riess said. Most treatment plants will require pre-treatment prior to the discharge. All applicable local ordinance provisions must be followed.
"If you're not using a sewer cleaning truck, you can initially inspect only the liquid. The liquid will settle on top of the solid. You can use a sump pump to collect the liquid from the catch basin, as long as you're not collecting any of the sediment with it," Riess said. Make sure that the water in the sump has not been contaminated. If necessary, collect a grab sample of the water and look for signs of contamination such as visible sheen, discoloration, obvious odor, etc. If there is any doubt of the quality of the water, it should be collected into a sewer cleaning truck and treated as waste under Part 121 or Part 115 Solid Waste Management (Part 115) of the Michigan Natural Resources and Environmental Protection Act (NREPA).
The clean water may then be directly discharged to one of the following:
- A sanitary sewer system (with prior approval from the local sewer authority)
- Curb and gutter
- Back into the storm sewer system, as long as it is contained within the system during dry weather conditions to ensure no discharge occurs into surface water
- The ground adjacent to the catch basin (evenly distributed at a maximum rate of 250 gallons per acre per year).
The remaining liquid and solid in the sump should be collected with a sewer cleaning truck and disposed of off-site in accordance with Parts 115 or 121.
The entity whose catch basin is being cleaned is responsible for meeting the generator requirements under Part 121.
The entity transporting the solid and liquid waste must meet the applicable transporter requirements. A local, state or federal government may use its own vehicle to service catch basins or other parts of the sewer system without being a permitted and registered transporter under the provisions of Michigan's Hazardous Materials Transportation Act (HMTA) of 1998.
If the local government contracts with a private company to transport the liquids generated from cleaning the catch basins or other parts of the sewer system, the entity must be registered and permitted as a uniform liquid industrial waste transporter under the provisions of HMTA.
The transporter must notify WHMD about their activity and obtain a site identification number. It is recommended MiTAPS at www.michigan.gov/mitaps be used to submit the notification and obtain the site identification number, or the facility may submit the form EQP5150 available at www.michigan.gov/deqwaste. There is a fee.
A uniform hazardous waste manifest must accompany the load, or a consolidated manifest may be used per Operational Memo 121-3, when the liquid waste is transported over public roadways by the local government or by a contract transporter. Records must be kept for at least three years from shipment. The waste transporting portion of the vehicle and/or containers used to transport the waste must be kept closed except when adding or removing the waste, and the exteriors must be kept free of the liquid waste and residue.
The facility accepting the solid and liquid waste must meet operating requirements:
- They must notify the WHMD that they are operating a liquid industrial waste designated facility, obtain a site identification number, and meet operating requirements under Part 121. This includes practices to prevent unauthorized discharge of the waste, sign manifests, and maintaining required records. If waste containers are used, they must be kept closed and protected from the weather, fire, physical damage, and vandals.
- The discharge of the liquids into the treatment plant that is permitted by WB must meet the wastewater treatment plant requirements. Any other discharge of the liquids would require a separate DEQ discharge permit.
- The resulting solid waste must be managed under Part 115 requirements. Dispose of the solid waste in a licensed landfill. Contact the landfill authority for their specific disposal requirements, including any tests they require to document that the solids are not hazardous or liquid waste. Do not use the solids as fill on local government or private property, or for any other use, unless it meets the conditions of being an inert material according to solid waste rules R299.4114 through R299.4118 under Part 115 of NREPA.
Street sweeping activities are also subject to the above solid waste requirements. Street sweeping involves the use of specialized equipment to remove litter, loose gravel, soil, pet waste, vehicle debris and pollutants, dust, deicing chemicals, and industrial debris from road surfaces.
"Generally, we want to sweep our streets as often as possible with the time and resources that we have available," Riess said.
Riess said that street sweeping has been proven to remove 50 percent to 90 percent of pollutants on paved surfaces. She pointed out that the street sweeping schedule will vary from community to community, the types of roads being used, the types of street sweeping equipment being used, and how frequently the equipment is used.
"Again, you want to consider prioritizing areas. If you have areas that you know collect debris on a quicker pace, move those areas up on your schedule. If you have a major construction project going on and you know that there is potential for sediment to get into the roadway, you will want to prioritize that area,"Riess said.
"Our goal is to prevent debris from getting into the storm sewer during a storm event." She said that it is important to do street sweeping before a storm event.
Riess said that the most common type of street sweeper used is the mechanical or broom sweeper. "These are generally good for picking up larger debris, however, we have learned that they aren't so good at picking up some of the fine sediment that gets into our waterways," Riess said.
"There are a couple of different types of vacuum sweepers — the dry and wet. A wet vacuum sweeper is used to help control dust. As the vacuum collects the material and the air is released, there have been problems with dust, so sprayers spray water to help suppress that dust. There are also some new types of dry vacuum sweepers that filter the air before it's released that negate the need for the water application.
"Some communities do a tandem operation where they will first go through with a mechanical sweeper to pick up the larger material and then they will follow behind with a vacuum sweeper to pickup the smaller debris.
"There is also a regenerative air sweeper, which also filters air before it is released. It uses an air blast instead of an initial vacuum in order to loosen the material and then it vacuums the debris. That type of equipment requires a seal with a pavement surface. If you're running into potholes, or if your roads aren't perfectly smooth, you might have problems with that type of equipment.
"Then there is the high efficiency sweeper. This is probably the most expensive type. It also uses regenerative air vacuum and filters air."
Riess also discussed a study that Tetra Tech did in 2001 in the Jackson area on the use of different types of sweepers, the amount of sediment they can collect, and the frequency that sweeping needs to be done in order to collect enough sediment that will make a difference.
"This study focused on an Elgin mechanical, various types of regenerative air sweepers, as well as a couple of the high efficiency sweepers," Riess said.
"They looked at a few different percentages of total suspended solids removal. Right now, the DEQ is in the process of revising the Phase Two permit. The draft language includes a 25-percent removal of total suspended solids on paved surfaces. So, keep in mind that that is a very real regulation in the near future.
"So, for a 75-percent removal rate, the only type of equipment that can achieve that is a high efficiency sweeper. And that is sweeping the residential areas and the highways every two weeks, and the business district and the industrial roadways every week. If you're looking at a 50-percent removal rate, the high efficiency and the regenerative air sweepers are able to achieve that. The high efficiency would be used on a monthly basis and the regenerative air every two weeks. So far, the mechanical sweeper cannot achieve the 50-percent or 75-percent removal rate.
"The mechanical sweeper is able to achieve the 25-percent removal rate, but it must be used on a weekly basis. If you're considering a tandem operation where you are going through with a mechanical sweeper and following up with a vacuum sweeper, then it would have to be done every two weeks in order to achieve the 25-percent removal rate. The regenerative air sweeper on its own would need to sweep the streets on a monthly basis, and the high efficiency sweeper would need to sweep every two months in order to achieve the 25 percent removal rate.
"You really need to look at the goals that your community needs. If you're looking at larger debris removal, a mechanical sweeper will probably be the way to go. If you're looking at water quality and suspended solid removal, you would need to consider a vacuum regenerative air or high efficiency sweeper. If you're using a dry vacuum sweeper, they have the potential to work all year.
"The street sweepings that are collected are designated as solid waste under rule 130. So, the proper disposal of street sweepings is to take them directly to a landfill. If you are stockpiling sweepings in your yard trying to accumulate a large enough load before you take it to a landfill, you can do that; however, there are regulations that cover that as well. You need to have secondary containment around the pile so that it is on a surface such as an asphalt or concrete pad and you want to make sure that you cover the pile with a tarp."
The Road Commission for Oakland County (RCOC) sweeps its streets approximately once every 13 weeks. "So, we're a long ways away from achieving a once-every-two-week sweeping on this system," RCOC's Bill McEntee said.
"A number of years ago, we did a cost analysis of us doing the street sweeping versus hiring a contractor to do it, and we determined that it was much more efficient to contract the work out. Dollar wise, contract services were about two-thirds of the cost of us doing it. The primary reason for that is that we are not able to make efficient use of the equipment. Street sweeping is the first fatality when something happens on the system that requires immediate response. So, many times we'd dispatch crews to do street sweeping, and they'd get called back."
McEntee explained that if a local government agency calls to let RCOC know that a manhole has failed, then that becomes first priority. "So, we found it much more efficient to use our labor and equipment to respond to those kinds of situations, instead of running the street sweeping program," McEntee said.
Dan Rooney, of the city of Farmington Hills, said that the city uses a combination of in-house and contractor street sweeping. The city contracts five sweeps per year from May through early fall, and in-house street sweeping is done on an as needed basis.
Erv Suida, of the city of Howell, said that Howell contracts its street sweeping operation. The central business district is swept twice each week. Major streets, local streets and state trunk lines are swept once every month or as needed.
"We specify in our contract that they use a mechanical sweeper and a vacuum sweeper. The reason we do that is that we do a spring and fall heavy debris cleanup, which requires a mechanical sweeper. Then they follow through with a vacuum sweeper to get the fine material. The routine maintenance also requires the vacuum sweeper," Suida said.
Gary Mekjian, of the city of Southfield, reported that the city uses a combination of in-house and contractor street sweeping. "We typically do local streets about eight times per year on curb and gutter sections, and four times per year on non-curb and gutter areas of the city. We try to do the major streets every 10 to 12 days, weather permitting," Mekjian said.
"We utilize mechanical sweepers. The vacuum sweepers are noisy, and our operators and residents don't appreciate that. They also have a higher maintenance cost. In the city of Southfield, they're not all that concerned about permit requirements; they care about curb appeal. The mechanical sweepers we have seem to satisfy those needs.
"Another reason we went with mechanical sweepers is that the traffic in Southfield is heavy and the sweepers we have selected have a higher rate of speed — about 15 to 20 miles per hour."