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A sanitary sewer success story

This article by Hala Baroudi, EGLE senior engineer, and Laura Verona, EGLE public wastewater unit supervisor, appeared in July/August issue of American Infrastructure magazine.

Michigan established a Sanitary Sewer Overflow Policy in 2002, in consultation with a stakeholder group, to correct illegal discharges to waters of the state. The story of one Michigan township – one of the first to enter a correction program under the policy – shows just how effective investing in improvements can be.

Located in Southeast Michigan’s Macomb County, Clinton Township is home to about 100,500 people. Nine sanitary sewer districts service its 28.2 square miles. From 2000-14, the township reported 86 sanitary sewer overflows (SSOs) – including 20 in 2011 alone and 12 each year in 2013-14.

Microtunneling work at installation of relief sewer along Little Mack in Clinton Township.

Microtunneling work at installation of relief sewer along Little Mack.

 

But since 2015, only eight overflows have been reported, two of them accidental releases unrelated to weather events that often drive overflows. Since 2017, the township has averaged less than one SSO a year. None have been related to wet weather.

About sewer overflows

SSOs are releases of untreated or partially treated sewage from a municipal sanitary sewer. They can cause serious water quality problems, back up into homes, cause property damage, and threaten public health. Possible causes include blockages, line breaks, sewer defects, power failures, and improper design.

Although SSOs are illegal, it’s not feasible to stamp them out completely or treat them all to meet the federal categorical secondary wastewater treatment standard. Enforcement discretion is allowable for communities that implement corrective actions – provided the actions meet the 25-year/24-hour storm remedial design standard, using growth conditions and normal soil moisture. Data analysis shows that communities implementing corrective action programs to this standard will have, on average, less than one overflow per 10 years.

Because SSOs are a result of many different circumstances, there are different approaches to correcting them.

The Clinton Township story

In 2000, Clinton Township entered an Administrative Consent Order (ACO) with the Michigan Department of Environmental Quality – forerunner to the current Department of Environment, Great Lakes, and Energy (EGLE) – to address SSOs in its sewer districts A and E. As a first step toward compliance, the township performed an Inflow/Infiltration study to evaluate flow from metering data collected over several months. A Sewer System Evaluation Study from May 2000-June 2001 consisted of extensive inspections, smoke testing, and televising to identify defects in the system.

Clinton Township Supervisor Bob Cannon inherited the sewer overflow issues and ACO when he took office.

“Those pump stations took the excess sanitary sewage and discharged it into the storm sewers that ultimately drain to Lake St. Clair,” he said. “It was an unsustainable solution to a Macomb County problem, but I’m proud we ended that practice.”

In August 2012, the township submitted to EGLE a hydrologic/hydraulic report for District A as the basis for designing capacity improvement projects to bring District A into compliance with the ACO and SSO policy. The first construction phase was completed in 2015 and the second in 2019. In August 2014, the township submitted a hydrologic/hydraulic analysis to bring District E into compliance. Projects were constructed in three phases, with the first completed in 2016, the second in 2018, and the third in 2019.

The ACO required Project Performance Certification (PPC) reports be submitted to EGLE by Jan. 31, 2020, for District A projects and by Feb. 1, 2022, for projects in District E. This report is currently under review. EGLE intends to formally approve the PPC in the next week or so, and the township will then ask to terminate the ACO.

“In 20 years, we have invested approximately $35 million in studying the problem and upgrading our sewer infrastructure to eliminate the sewer overflows,” Cannon said. “We have worked successfully with EGLE and their staff on resolving sewer overflows, and we will continue to follow through on a good sanitary sewer asset management plan to make sure no sanitary sewer overflows happen again.”

In all, the original ACO was amended six times to add construction projects and data collection/evaluation. Projects include cured-in-place-pipe (CIPP) lining, manhole rehabilitation, and correction of sewer system deficiencies found in smoke testing, coupled with installing relief sewers and wet-weather pumping stations.

In doing so, Clinton Township has been successful in addressing the requirements of the ACO and meeting the design criteria set forth in EGLE’s SSO Policy.

Hala Baroudi, P.E., an EGLE senior engineer with more than 30 years of experience, is accomplished in hydraulics and hydrology, the design of sewer and water distribution systems, and computer modeling. Laura Verona, P.E., EGLE’s Public Wastewater Unit supervisor, has more than 25 years of experience in drinking water and wastewater engineering.