There was a time when concern about stormwater was simply to keep it off the street with a collection system able to handle a 10-year storm. Now, thanks to increased knowledge—and increasingly stringent regulations—the goal is to ensure that storm events don't overpower an existing system and carry solids and petrochemicals to lakes, rivers, detention ponds, manmade wetlands, and oceans. Solutions can range from floc logs or cartridges light enough to carry to concrete baffle boxes larger than a commercial garage. Keep It Cooperative
Older communities are especially challenged. An example is Worcester, MA, a city of 165,000. "Part of our collection system goes back to the Civil War era," explains Matt Labovites, director of sewer operations. He adds that about 15% of the system is combined (chiefly in the oldest part of the city); the rest consists of separate storm and sanitary sewer systems.
"We were a Phase I community for the NPDES [National Pollutant Discharge Elimination System] and had a stormwater management program up and running in 1993, with a permit finally issued in 1998. We had to devise and implement a management program in an area that gets 48 inches of rain a year. Our solutions have included a whole series of BMPs [best management practices], general and specific, including detecting and eliminating illicit connections." Education has been an important element as well, informing citizens how their behavior affects stormwater quality.
"We're the headwaters of the Blackstone River, which gives us a lot of opportunities to partner with local watershed associations, and we tout the fact that we've established a very good rapport with all of these groups," Labovites says. Site work includes the installation of a Vortechnics Vortechs model 16000 on the banks of Lake Quinsigamond, which is 7 mi. long and a major recreational water body. "Originally the project was to upsize the pipe to eliminate a capacity issue. Now we're able to address a quality issue as well, because in the four years it's been on-line, it's kept 25 cubic yards of sediment and materials out of the lake. And that's material that's made it past our catch basins in a 226-acre drainage area." (There are 15,000 catch basins citywide.)
The city checks the separator quarterly and has cleaned it three times in four years. Labovites says the only challenge to cleaning is the hillside the vehicle has to traverse to reach the separator. "Experience has helped reduce cleaning time from one and a half days the first time to less than a day. The vast majority of that pumped material is sand and sediment, with less than 10% trash, so it goes directly to the landfill. There are now a handful of separators around the city, with most installed by developers upon construction, then turned over to the city for ownership and maintenance."
Keep It Clean
Although many products and systems are on the market to help a company or municipality control specific stormwater pollution problems, the general need is to keep the system working by maintaining clean inlets or catch basins. "Most cities have some sort of PM [preventative maintenance], whether their own or contracted out," points out Paul Wagoner, products manager for Aquatech Products for HiVac Corporation in Marietta, OH.
Wagoner offers some tips for effectively removing solids on a PM basis. He recommends getting a vacuum that can handle dirt, sand, rocks, stones, bottles, cans, and even car parts. "The need is to remove solids so they don't clog the system and cause a stormwater backup into the street. That vacuum needs to work underwater so the contractor or municipal operator doesn't have to first remove the water, which can be thousands of gallons. But with a positive displacement exhauster as source of vacuum, the contractor can go right to the bottom and remove the debris. This usually opens up the basin so the backed-up water can discharge down the line as originally intended."
The goal is to schedule maintenance when the line is dry. "For cleaning with a handheld gun, look to about 800 pounds per square inch [psi] and about 15 gallons per minute [gpm]. When you're cleaning lines between catch basins, the more material you have to move, the higher volume of water you need. Pressure, which can be 2,000 psi or more, is good for scouring scale, but everything on the bottom of the pipe has to be flushed, and 80 gpm will handle a dry pipe. That pressure will flush debris back to the catch basin, where you can vacuum it out. The more water you have, the less work it is." If the pipe is underwater, though, that need can easily climb to 150 gpm.
"Other elements to consider include ease of operation of the truck, particularly when you're setting up over a manhole," Wagoner continues. "Our vacuum boom has a 360° rotation, and operators usually are able to vacuum more than one catch basin before moving the truck. Storm sewers are almost always on the corner of the curb, so a hose reel on the back of the truck makes it a relatively simple set up for cleaning storm sewer lines."
One of the users of the technology is Lake County Sewer Company Inc. in Willowick, OH, which offers a variety of services nationwide to help get storm systems back on-line. CEO Rick Marucci lists some of the challenges of dealing with catch basins and inlets: "Municipalities are not cleaning their storm sewers often enough. Another [challenge] is the cost of placing the pumped material in the local landfill. We can save as much as 25% on dumping fees when we first stockpile what we've vacuumed out for a few days so it can dry out." Stockpiling also gives the operator time to have loads tested for landfill acceptance. Water from the temporary stockpile remains in a lined pond area to evaporate.
Catch basin cleaning takes about 30 minutes, including five minutes for washdown. Lake County Sewer technicians first remove the lid, lower the vacuum tube, and start vacuuming. They don't add water because of the weight concern but do have water on the truck to wash down the walls. Each truck uses 2,000 gal. of water a day, running 2,500 psi and 80 gpm, using 40-50 gal. per basin.
"Changing regulations have outdated some systems," Marucci observes. "Municipalities have to retrofit, for example, adding liners to catch oils, antifreeze, petrochemicals. We're in the Cleveland area, and our storm system goes right to Lake Erie, so the cities have built retention ponds in the past two years. But what will they do when those ponds are polluted?" These ponds buy time to come up with a permanent solution.
Keeping It on the Work Site
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Another challenge, especially for building contractors, is to ensure that projects don't become part of the problem. "We believe in stopping silt at the source, at each inlet, aboveground, where it can be easily assessed for maintenance," explains Roger Singleton, CEO of Silt-Saver Inc., a pioneer firm in sediment control. Speaking from his Conyers, GA, office, he counsels, "While in the design stage, a hydrology study determines the potential volume of water runoff. Then pipes are sized and a stormwater plan developed. During the sequence of grading and road building, the drainage system is the first infrastructure installed. Upon completion, the installation allows for proper drainage while further development goes on: water, curbing, paving, et cetera. As soon as the first pipe or inlet has been installed, the contractor using our assembly is able to completely protect the inlet from erosion and provide a safety cover. This takes about five minutes and requires only one man with a shovel.
"As a participant in the ‘treatment train,' we recommend a 2-inch- to 3-inch-wide collection area, below grade level, around each inlet," advises Singleton. "This allows the silt to be collected at each inlet in smaller quantities, aboveground, before stormwater enters the clean pipes that lead to underground retention areas or to the streams. While underground storage and various catch basin insert types are effective, they need to be kept free of silt during this time. We find that prevention, through the use of performance-based products, is more effective and better economically than the alternative: fines, vacuum trucks, or the pollution of our streams."
Site control gets a major emphasis in California, with catch basin and inlet protection devices a close second. Points out Hossain Kazemi, a senior specialist with the California Regional Water Quality Control Board, "To protect the water, the state, and the benefited users, California issues permits for construction, and everybody has to follow the standards, which reflect the NPDES requirements. Come March, every California city with at least a 10,000 population will have to have a BMP-based stormwater protection plan in place, and so will contractors building on sites an acre or larger."
He emphasizes, "The best way to minimize mud during construction is to have erosion control. Cover the site with blankets and mulches that can absorb the blow from raindrops falling at 20 miles per hour and keep the water on-site. Let nature take care of it rather than putting everything in the pipe and treating it at the end of the pipe. For a second line of defense, silt fencing, fiber rolls, and sediment traps help protect catch basins and inlets. The ongoing challenge is maintenance. Who is going to make sure the inlets and catch basin protective devices are kept clean and functioning?"
David Kelley, national marketing manager for ACF Environmental in Richmond, VA, agrees. "People need to remember that products like the Siltsack catch basin filter [produced by ACF] are designed as a secondary line of defense to keep sediment, trash, and debris out of catch basins and storm sewers. They need to have other measures on the job site to keep construction sediment on-site. But private contractors as well as cities, [departments of transportation], municipalities, and government sectors are learning that secondary protection measures are cost-effective, especially for long-term protection of existing stormwater systems."
Kelley says the basin filter can be installed in minutes, with cleaning and maintenance taking less than 10 minutes. "For maintenance, it's a matter of removing the grate, pulling out the sack and emptying it, then perhaps hosing the sack so it will continue to let water through." Another ACF product, the Gutterbuddy, complements the catch basin filter and also can be recleaned in about 10 minutes. Kelley emphasizes that regular maintenance is key to longer product life, which can be upward of three years.
"The purpose of catch basin technology is to remove pollutants, including petroleum hydrocarbons, litter, debris, silt, sediment, vegetation, and even heavy metals, before they have a chance to enter the drainage system," says Doug Allard, president of KriStar Enterprises Inc. in Santa Rosa, CA, designer of the Flo-Gard catch basin insert.
"Flo-Gard systems can be installed in an existing drainage system without modification of the system and are suitable for new projects," Allard points out. "The technology is very adaptable to the treatment-train concept for long-term BMPs, where it can be used in conjunction with other technology farther downstream, such as detention ponds, grassy swales, and the like." Thus, catch basins and detention systems work together to ensure that fewer pollutants reach lakes, rivers, and bays through stormwater runoff.
Keep It Light
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For older cities, a major challenge is to meet the newest regulations regarding phase-separated petroleum hydrocarbons, sediments, and floatable pollutants typically found in runoff flows without having to overhaul the entire system. "Most of the infrastructure is in the ground, so how do you correct millions of storm drain inlets?" asks Ron Woerpel, president of Advanced Aquatic Products International in built-out Key West, FL. "Water rushing in a drain is like a giant blender. You need something during the first-flush phase that skims the surface, takes off the petroleum, and helps lock that petroleum into a solid for handling and disposal safety." For such typical problem areas as parking lots, gas stations, and chemical plants, one answer is the Hydro-Cartridge, developed by Jorge Sainz of Geotechnical Marine Corporation in Miami, FL. Woerpel and Sainz met during the 1994 Miami Boat Show, and they joined forces, matching the Hydro-Cartridge with Woerpel's Bilge Bud-e's polymer filter, and creating a device designed to handle hydrocarbon intrusion on a long-term basis. That product was rated number one in the March 1999 Rogue River Test for hydrocarbon removal.
"We were one of the first companies to recognize the need for stabilizing the collected runoff pollutants for long-term disposal safety," points out Woerpel. "Essentially it is a vertical weir. This allows for immediate capturing of phase-separated pollutants [primarily petroleum hydrocarbons] thanks to the detention time at the inlet funnel of the unit. Solids [density greater than 1.0] will precipitate to the bottom of the unit. If maximum holding capacity is reached, it will self-flush to prevent ponding; therefore it has a built-in bypass capability and doesn't later become part of the problem."
He adds that installing the fiberglass box is relatively simple. "It hangs from the frame and provides detention time so fuels and other hydrocarbon waste can be captured and later removed. It also helps prevent buildup of debris in the underground pipe, which helps keep the future costs of pipe cleaning down for the cities. The box weighs less than 35 pounds and takes one person about a minute to install it, after the grate has been pulled and the frame cleaned. Filter replacement scheduling can range from three to six months."
Jacksonville Airport Authority, which operates some of Florida's various airports, finds Hydro-Cartridges and baffle boxes an economic solution for controlling site runoff year-round. Dave Dunckley, environmental coordinator for the airport, reports that the system is able to catch chemicals from both cars and airplanes. "We've installed 28 Hydro-Cartridges, including two in our parking area, to keep hydrocarbons from getting into the watershed during a storm event. We change filters every two or three months, and maintenance is relative simple."
He says the airport used to rely on detention ponds. "But ponds attract birds, which you don't want around airplanes. With baffle box technology, we're able to capture solids, which then are pumped from the boxes every six months to a year. We also have swales to prevent offsite runoff, but the need is to have those dry within 48 hours to avoid turning them into mosquito breeding places. We hold the tenants responsible for keeping their individual sections free of debris and pollution runoff, and I oversee the whole airport. With tenant care, baffle boxes, and Hydro-Cartridges, we're able to meet our stormwater challenges."
When There's Already a Problem
Advanced Pipe Inspection Inc. (API) in Boston, MA, deals with everything from pipe inspection, pipe cleaning, and catch basin cleaning to trenchless cured-in-place pipe repair and nondestructive excavation. API President Joe Walsh says his 10 full-time employees work year-round, except during active storms. His equipment lineup includes Pearpoint inspection equipment, Aqua Tech and Vactor combination machines, and Stetco catch basin trucks. "A majority of our equipment is less than three years old and built to our specifications," he adds.
Providing service to industries and municipalities throughout New England presents a number of challenges, and the age of the infrastructure is a major issue. Others of note: Development has reduced available green space and the increasing population puts additional stress on aging systems.
Walsh gives this example from a wastewater treatment plant in Connecticut: "A 76-inch pipe feeding into the plant had been broken and had taken in a lot of sediment, which was interfering with operations and damaging plant equipment. We responded immediately and spent the next two weeks removing more than 200 tons of sediment. Our timely response helped ensure that the plant could continue operating and prevented additional damage to the plant's equipment and the surrounding environment."
API recently cleaned 17,200 catch basins in Boston, removing an estimated 50,000 tons of sediment. The work had to be completed within 450 workdays and included jetting the laterals to the storm drains. To work throughout the winter, API mounted a jetter in the back of an insulated cube van so that the heat from the jetter's engine allowed them to move from basin to basin without freezing up.
Keep It Working
While regular maintenance helps keep litter and pollution control devices operating, there's still the risk that the prevention device will be overpowered during a particularly strong storm event. Enter the continuous deflective separation (CDS) process. "This process, which requires no moving parts, was developed in Australia and is ideal for applications where gross solids, sediments, oils, and floatable pollutants need to be removed from stormwater or combined sewer overflows," explains Chris Landt, regional manager of engineering services for CDS Technologies in Winter Park, FL.
"A significant issue in stormwater treatment is that many municipalities have outfalls that have never been treated. An increased awareness of stormwater pollution and new regulations, such as NPDES, have led communities to retrofit a variety of stormwater BMPs. With CDS, the community can treat large basin areas with a single CDS device, in one location and with a small footprint. This decreases maintenance and construction costs," Landt points out. The devices range from 5 to 15 ft. in diameter. The smallest unit, which is designed to treat as little as 0.6 ft.3/sec., can be installed in less than a day, while the largest, with a treatment capacity of 64 ft.3/sec., might take upward of two weeks, depending on the water table, site conditions, and traffic control challenges.
These units capture fine sediments and gross solids and are capable of removing more than 80% of annual total suspended solids from stormwater. Explains Landt, "CDS units are the only devices on the market that employ a self-cleaning screen that will ensure removal and permanent retention of particles equal or greater than the screen opening size [2.4 to 4.7 millimeters], regardless of the specific gravity of those particles." A diversion weir is designed to bypass excessive flows around the treatment chamber without resuspending captured material.
"Additionally, these units remove 100% of floatables and 100% of all particulates equal to or greater than one-half the size of the standard screen opening of 4,700 to 2,400 microns [0.185 to 0.095 inch] when the CDS is operating at its treatment capacity. A conventional oil baffle, coupled with sorbent material, can permanently capture 80% from influent concentrations as low as 25 milligrams per liter," Landt states.
Keep It Local, Logical
"Anyone who wants to meet local and federal regulations has to know their own soils well," says Tina Thomas, marketing director for BaySaver Inc. in Mount Airy, MD. "They need to keep track of which methodology to use and look for different ways to maximize the selected product. This industry is really young, and there's a lot of fieldwork involved to make sure the BMPs are economical and meet regulations. That's why part of our strategy is to make local presentations and be sure everyone's speaking the same language."
BaySaver Separation Systems are designed to remove free oils, suspended solids, and floating debris from stormwater runoff. "They're driven entirely by gravity," explains Thomas. "The flow enters the primary manhole for initial separation, then is treated a second time in the storage manhole, where fine suspended solids and floatables are collected. Since the water flow is regulated into the secondary manhole, resuspension risk is minimized."
Protecting the Tax Base
Water flow is a major factor in Pensacola, FL, which averages 62 in. a year, with much of it from storms. As the city grew, the existing stormwater system became dramatically inadequate, and stormwater ran directly into the bays and bayous. The city sought bids for long-term solutions, and the winner was Baskerville-Donovan Inc., a full-service engineering firm headquartered in the city. Project Manager Mike Langston says, "There are 40 square miles of drainage here in Pensacola, and the city's goal is to retrofit the entire system without having to buy additional property to do it. Buying property reduces the tax base, and they don't want to take away from the tax base."
He gives the example of the East Hill Stormwater Treatment Enhancement Project, a project Langston's company has been working on for about 14 months and expects to complete in spring 2003. The 200-ac. site is primarily a residential and commercial area that dates to the late 1800s. The city was dealing with flooding issues and had done its design work for pipe sizes and structures before Baskerville-Donovan joined the fray. "Drainage waters into Bayou Texar were impaired with bacteria, sedimentation, nutrients, and just plain trash. There was very little treatment of the 200 acres prior to dumping directly into the bayou. Our task was to provide stormwater treatment for the system the city had just upgraded."
The company went as far upstream as possible to the trunk line, dividing the upper half of the drainage area into small basins that would use its 5K BaySaver and put five structures in place. "That area has a lot of oak trees, so screens won't work because of maintenance problems," relates Langston. "But the BaySavers, with their primary and secondary chambers, can handle the leaves and debris to avoid clogging and consequent overflow during a storm event." They're installed to the side of the storm line so they can be bypassed during major storms.
Downstream, the storm sewer passes through two city parks. That's where Baskerville-Donovan installed four baffle boxes to catch leaves and other litter. Langston adds, "Each box is 24 feet wide, 62 feet long, and 10 feet deep, with the bottom of the box set 15 feet below grade. We kept the poured-in-place baffle boxes and the BaySavers at 15 feet because the city's vac trucks are limited to a 15-foot pull." Dividing the 200 ac. into two sections allows the downstream 100 ac. to be treated before stormwater from the upstream 100 ac. reaches it. The strategy also helps to slow stream flow at the lower end of the site to less than 0.3 ft./sec. so that 60-70% of suspended solids fall out of suspension and are captured in the baffle boxes. Now both the soil and the tax base are erosion-proof.
Keeping It in Despite the Storm
Another challenge is keeping the pollutants at the collection point until they can be gathered. One solution used at nearly 10,000 sites in North America and Australia is the Stormceptor, which is installed in a fashion similar to a manhole. "The concrete Stormceptor components go vertically down an average of 18 feet to the bottom," says Scott Monteith, vice president for Stormceptor Corporation in Alexandria, VA.
It was invented to be a sophisticated front-line inspection device for industrial and commercial properties. "In theory, the product is installed at the property line to intercept oils and sediments and store those pollutants in its storage chamber. Its internal bypass is designed to protect those pollutants from scouring or flushing during high-flow storm situations and to treat 90% of annual rainfall events," Monteith describes. "We target the product for small industrial and commercial developments, shipping ports, and highways." It's also used in military and residential applications to protect ponds and wetlands. Whether applications are commercial, military, or residential, semiannual inspections to determine accumulation keep long-term management relatively simple. Secure storage of solids and liquids helps makes debris collection an easy task.
The solution to meeting today's mandates for stormwater runoff is straightforward: find the right tool or device, then follow the directions to ensure that it will continue to perform in the years to come.