Storm water overflow

December 1, 2014

Water and other liquid refuse flowing through the miles of sewers in Oakland County flow downhill. So, when more than five inches of rain fell during a three-hour period in August across southeast Michigan, more than two billion gallons of partially treated sewage also traveled downhill, journeying from southeast Oakland County into the Red Run Drain in Macomb County. It was much more than the system could handle, with all local systems overflowing, flooding sewer systems designed to capture the overflows, as well as roads, highways, and thousands of homes and basements.

The overflow was just one of more than 35 that originated in Oakland County that was recorded by the the Michigan Department of Environmental Quality (MDEQ) during 2014. In total, more than 2.4 billion gallons of storm water, sewage or partially treated sewage that originated in communities in Oakland County and later entered area surface land or waters rather than their targeted treatment plants. However, state and county water resource managers say efforts to control the number of sewage overflows, as well as the water quality of them, has vastly improved from years past.

Sewer overflows are a situation where mostly untreated sewage is discharged into the environment before it has been able to reach its appropriate treatment facilities. Wet weather overflow is the reason when it’s caused by unusually heavy rainfall, either from the infiltration or inflow of excessive storm water into sewer lines during a heavy rainfall; because of a rupture in a sewer line; or the breakdown in a pumping station due to a power failure. 

Of the more than 2.4 billion gallons discharged from area sewers, all but about 14 million gallons had been partially treated before being released into the environment during 2014. While still a tremendous amount of water, compared to the amount of water processed by sewage systems, it was a drop in the proverbial bucket. Of the about 14 million gallons, more than 10 million gallons of the overflows during this year contained diluted sewage from combined sewerage overflows, or a mixture of raw sewage and storm water. 

Sewer systems throughout Oakland County primarily funnel both storm water and sewage to their required locations without any hitches. Yet the sewer overflows which do occur throughout Oakland County happen because the designs in the systems, which developed during its earliest years in the southeastern portion of the county, prior to the 1940s, actually lend themselves to more overflows during heavy rain events. That’s because the majority of the sewer system in the area are part of a combined sewer system, meaning they carry both storm water from local catch basins, as well as sewage from people’s homes and local industry. After the 1940s, newer communities were developed with separate storm water and sanitary sewer systems.

“Southeast Oakland County was some of the first land developed, and because of that, a lot of that is a combined system,” said Gary Nigro, assistant chief engineer at the Oakland County Water Resources Commissioner’s Office. “A lot of the northeast portion of the county, and other areas, they have separated sewers for storm and sanitary. Things are being looked at in southeast Oakland County, like Birmingham, Troy, Madison Heights, Royal Oak and those areas.”

Raw and inadequately treated sewage that is discharged from municipal systems has been a problem in Michigan for decades. But according to the MDEQ, the state took a more aggressive approach to address discharges in the late 1980s and subsequent years. However, to better understand the issues that lead to overflows, it’s first necessary to understand how sanitary and storm water sewer systems work. 

Sanitary sewers are designed to carry only sanitary sewage to a wastewater treatment plant, while storm water is designed to be directed to nearby rivers, lakes or streams through a system of storm sewers. 

Sanitary wastewater is treated in several stages, involving primary and secondary treatment states, and a final disinfecting stage. During the primary stage, nearly half of the solids in the wastewater is removed. This removal is often done through screens and grit chambers that utilize sand, grit and other materials. 

The secondary stage removes about 85 to 90 percent of the remaining pollutants. One method used includes the use of an aeration tank, followed by a secondary sedimentation tank. In the aeration process, air is mixed in the tank and microorganism concentrations are kept high to speed the consumption of the organic matter. The microorganisms and other solids settle to the bottom of the tank during the sedimentation process and are removed. After that, a disinfectant such as chlorine is often used to kill disease-causing organisms before the wastewater leaves the treatment plant. 

When sanitary sewers become clogged or malfunction, a sanitary sewer overflow (SSO) may occur, resulting in the discharge of raw, untreated sewage

“Sanitary sewer overflows are illegal. That’s a discharge of raw sewage,” said Laura Verona, southeast Michigan district supervisor with the MDEQ Water Resources Division. “If you look at communities that have issues with that, they are under an administrative order with us. Typically, they have a problem and they go in and fix it. A corrective action doesn’t necessarily mean enforcement.”

When an SSO occurs, raw sewage may be released into basements, city streets, properties, rivers and streams. Such overflows are illegal, but they may occur during wet weather conditions when sanitary systems receive storm water in-flow or infiltrating ground water. When they do occur, it’s obvious that the system has malfunctioned.

In addition to sanitary sewer systems, many older communities, like Birmingham, operate on a combined sewer system, meaning that the sewers carry both raw sewage and storm water in one pipe. Such combined systems are designed with overflow points because the sewer system can’t handle all the volume of water that is associated with some larger storm water events. 

Combined sewer systems are designed to collect snowmelt, rainwater runoff, domestic sewage and industrial wastewater in the same pipe. Most of the time, combined systems transport all the wastewater to a sewage treatment plant where it is treated and then discharged into a body of water. During heavy rainfall or massive snowmelt, however, the wastewater flow rate in a combined sewer system can exceed the capacity of the sewer system or treatment plant. Because the combined systems were designed to overflow into local water bodies during significant wet weather events, combined sewer systems have historically been among the major sources for beach closings and other water quality issues.

“A sanitary sewer overflow is raw sewage,” Verona said. “A combined sewage overflow is a combined system, so you have both. It’s diluted sewage, but (it’s) an untreated discharge.”

Both Combined Sewer Overflows (CSOs) and Sanitary Sewer Overflows (SSOs) can result in the release of untreated human and industrial waste, toxic materials, debris, and disease-causing organisms onto the ground or into area rivers, lakes and streams. 

About 13.74 million gallons of combined wastewater was released into surface water in Oakland County due to rainfall in 2014, according to records available from the MDEQ. 

“An untreated CSO is when the system capacity is exceeded and you have a discharge, or it will back up into people’s basements,” Verona said. “With the retention treatment facilities, the water is treated. It goes to these retention basins and it is treated before it is discharged.”

Prior to 2004, only releases from municipalities were required to be reported to the MDEQ. However, the National Resources Protection Act was amended to include the reporting of treated and partially-treated sewage releases from private systems that serve more than a duplex. When raw or partially-treated sewage is released, the responsible party is required to notify the local health department and other entities specified under the law. 

To reduce the amount of sewage entering an area’s waterways, engineers design and install retention facilities to hold water during rain events. Retention treatment basins are designed to capture the combined sewage and rain water that would otherwise flow to surface waters untreated. The basins hold the combined sewage long enough to provide treatment and disinfection before the combined sewage is discharged into waters during heavy rainfall. The basins also capture sewer system releases during smaller rainfall events and return all of the captured sewage and rainwater back to the system to be routed to the wastewater treatment plant for treatment. 

Retention basin discharges are treated discharges from the retention facilities, which are designed to meet permit requirements and be protective of water quality and public health, according to the MDEQ.

The largest overflows originating in Oakland County come from retention treatment basins that become overwhelmed by heavy rain events. The largest contributor to overflows is the George W. Kuhn Retention Treatment Basin, formerly known as the 12 Towns Drain. It serves all or part of 12 communities, encompassing a drainage area of 24,500 acres upstream of the Red Run Drain, which is a tributary of the Clinton River. It is one of the largest screening facilities in America, according to Headworks, a Texas wastewater screening company. During normal, dry weather, all flow is routed to the Detroit Wastewater Treatment Plant. But, during unusually heavy rainfall, heavy volumes of combined sewage (typically made up of more than 93 percent storm water) exceed the capacity to the Detroit plant, causing the overflow to be diverted to the Kuhn retention basin, where it is stored, screened, and disinfected prior to discharge into the Red Run Drain. 

“The intensity of the rain makes a huge difference in how the system reacts,” Verona said. “In August, that was about 5.5 inches of rain, so the George W. Kuhn Retention Treatment Basin ended up discharging about 2 billion gallons of combined sewer overflow. But, a few years ago, we had a rainstorm that was about 5.5 inches, but it came over the course of three days. We discharged about 1.6 billion gallons, but there was no basement flooding because it came over three days. The one we got in August was over three hours. If it’s a slow, steady rain, we will never have an issue.”

In 2014, a total of about 2.419 billion gallons of partially treated wastewater from the Kuhn retention basin was released into the Red Run Drain.

The Beverly Hills/Birmingham retention plant, which receives its flow from a combined wastewater, like the George Kuhn retention basin, discharged millions gallons of water in 2014 due to rain or snowmelt. Each of the discharges fell within the facility’s permit, according to the MDEQ. 

The largest discharges, outside of those connected to the George Kuhn retention basin, occurred in August in Birmingham and Beverly Hills. On August 11, about 5.46 million gallons of partially treated sewage was released from the Birmingham retention treatment basin to the area of Lincoln and Southfield roads. About 11.43 million gallons of partially treated sewage from a combined treatment facility was released the same day from a retention basin to drains near Cranbrook and 14 Mile roads that lead to the Rouge River. That release came on the heels of a similar discharge of 14.06 million gallons of partially treated sewage at Evergreen and Beverly that also went to the Rouge River.

Separate from the one day catastrophic event on August 11, the majority of sanitary sewerage overflows, or SSOs, that occurred in 2014 in Oakland County happened due to malfunctions or failures in the system. For instance, 22,640 gallons of raw sewage was released on September 1 when a syphon, a tube used to convey liquids upwards from a reservoir, under the Clinton River plugged, causing an upstream manhole cover to overflow, spilling raw sewage onto the banks of the river.

While the Kuhn retention basin is the largest contributor of overflows in the Oakland County system, Nigro said work done to the drain over the years has greatly reduced the number of overflows, as well as improved the quality of water being released. The retention basin consists of a two-mile long drainage system that is 60 feet wide, which runs mainly through Madison Heights. The underground basin holds about 124 million gallons.

Nigro said prior to improvements to the George Kuhn retention basin, which receives its flow through a combined sewer system, there would have been roughly 50 discharges into the Red Run drain each year, or basically each time it would rain in southeast Oakland County. Mandates by the state required the county to take action to reduce the number of discharges, and weir structures were installed to allow water to be stored in the system.

“That took discharges down to about 25 a year,” Nigro said. “A few years later, the state said, ‘you can do better,’ and they built this enormous retention basin in the Red Run Drain,” he said 

The retention basin runs underground from the area near 12 Mile Road and Stephenson Highway to Dequindre Road, just north of 13 Mile Road.

“That took us down to about 12 or 15 discharges a year, and it stayed that way for about 30 years,” Nigro said. “The idea is continual growth. In 2003 or 2004, we added another 30 million gallons of storage, and a big screening facility. We improved the chlorination system to make it more efficient. We are down to about eight or nine discharges a year, so the quality keeps getting better. The MDEQ recently came to us and wants us to cut that number in half, again. I’m not sure what improvements we can make to the facility without a $100-million price tag.”

“The GWK is one of the most impressive facilities of its kind in North America,” Oakland County Water Resources Commissioner Jim Nash said. “I’m extremely proud of the extraordinary progress GWK has made over the years in reducing combined sewage overflows and maintaining the highest water quality standards possible.”

Nigro said further reducing overflows may be done by implementing “green infrastructure,” rather than building a larger basin. The approach means using more porous pavements that can capture water and allow it to flow through the pavement, rather than allowing it to run off, and other improvements that reduce the amount of water entering the system.

The state of Michigan took a large step forward in 1988 when it initiated a CSO control program, while in 1994, the federal government developed a nationwide CSO control policy. The policy suggests that states use an enforceable mechanism, preferably a permit program that was initiated by the federal Clean Water Act, called the National Pollutant Discharge Elimination System, which required communities to implement new measures to control CSOs.

The program included developing long-term control plans using nine minimum controls, according to the MDEQ. Those controls basically included interim measures that could be taken to begin addressing the CSOs before major sewer system construction activities would be undertaken. In Michigan, all municipalities with CSOs have completed the required measures and developed long term control plans. 

The long term control plans must assess a range of control options, including costs and benefits, and lead to selection of an alternative that would meet federal and state clean water laws. Since the cause of CSOs is an excess of rain or snowmelt, some municipalities have decided to separate their combined sewers, thereby redirecting the clean water runoff to lakes, rivers and streams via storm sewers. However, storm sewer separation projects are expensive, and often involve extensive utility and road reconstructions. 

In Oakland County, a more common way of addressing CSOs has been to build additional treatment or storage basins to contain a portion of the volume and provide treatment of any resulting discharge. Specifically, as part of the final corrective program, many owners of combined sewer systems have installed or are installing Retention Basin Treatment facilities.

Currently, the Oakland County Water Resources Commissioner’s Office is working on a $46 million project that would add 3.7 million gallons of retention capacity to the Evergreen-Farmington sewer system. The project will consist of a 7,600 foot tunnel, 9-feet in diameter, to provide additional sewage capacity for the existing Farmington gravity sewer interceptor, located on Middlebelt Road between 13 Mile Road and I-696. The tunnel will vary in depth from 40 to 80-feet below the surface of Middlebelt Road. 

One of the actions the DEQ has taken to address overflow problems is through the the state’s Stormwater Asset Management and Wastewater (SAW) program, which helps municipalities plan for sewer system maintenance. The program provides grant assistance for developing storm water and wastewater project planning and design, asset management plans for wastewater and storm water systems, storm water management planning and testing, and demonstration of technology.

In October, the MDEQ awarded about $91 million to municipalities throughout the state through the program. The grant awards are the second round of SAW grants, with a total of 207 municipalities across the state receiving grants, totaling about $170 million, including a $1 million grant to Commerce Township.

Commerce will receive funds through January 2017 from the program, with the township matching $109,944 of the total amount. The funds will go to develop an asset management plan for the wastewater collection and treatment system, design and engineering costs related to the abandonment of the Welch Road, Haggerty Road and Commerce Towne Center Pump Stations. The grant will also help to fund the development of a sanitary sewer asset management plan. 

Nigro said asset management and plans created through the SAW program will help to identify issues before they become problems.

“I like to think that, as far as asset management, we are already ahead of the curve,” he said.

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