City Cleans and Inspects More Than 8,000 ft of Brick Interceptor, Ranging 66 to 102 in. in Size
The City of East Chicago, Indiana, came across a major problem during the start of a large housing redevelopment project – drainage was not functioning properly. Their investigations led them to a brick interceptor originally from the early 1900s that was at or near capacity.
East Chicago was incorporated into a city in 1893 and within a few years the key development of the Inland Steel Plant was founded in 1901. In 1907, the Indiana Harbor Ship Canal was dredged to further grow the booming steel manufacturing industry in the area. With the growth of the industry, the city anticipated the population to grow as well, and needed infrastructure to support this growth.
The City of East Chicago’s population grew from 3,400 to 19,100 people from 1900 to 1910 and was more than 50,000 by 1930. The Alder Street Interceptor was built in 1907 in the Indiana Harbor area, one of the oldest sections of the city, and is still in use today.
R&R Visual Inc., out of Rochester, Indiana, has been working with the City of East Chicago since 2019 to inspect and clean nearly 8,000 ft of brick interceptors ranging in size from 66 in. to 102 in. Due to the high-water levels, R&R Visual had to mount its inspection camera to a custom-built float to help navigate down the lines.
After the first initial inspection using RapidView IBAK CCTV inspection equipment, it became clear to the team that a sonar inspection would be necessary to quantify the volume of debris underwater where conventional CCTV wouldn’t be able to see.
The caliper head of the sonar inspection unit was positioned at the manhole and pulled through at a specified rate while capturing 360-degree profiles at set increments. It echoes sonar frequency from the pipe walls to measure the distance from the head. Each distance reading is stored with the head’s relative position (in degrees) to the top of the pipe. These readings allow the software to generate points in a three-dimensional (3D) space to create a profile ring at the given distance.
During the sonar inspection, it was determined there were significant capacity issues. They identified that the lines had more than 50 percent of debris built up for nearly two-thirds of the way to the lift station. Several critical sources of infiltration and inflow were identified, which means groundwater and stormwater were getting into the sanitary sewer system that should only contain wastewater, as well as numerous amounts of calcium deposits.
After analyzing the inspection reports, the next step was to begin the removal process of the grit and debris that had been accumulating in the Alder Street interceptor for more than 100 years. With this degree of build-up, specialized equipment would be necessary for removal. Another contractor, Doetsch Environmental Services, was contacted due to its experience in large-diameter sewer cleaning.
The cleaning equipment was set up for up to four weeks at a single location due to the consistency, volume, and distance cleaned. As the grit was vacuumed out of the interceptor, the water was effectively recycled back into the line. It wasn’t uncommon to fill a 12-yard (approximately 20 ton) debris box multiple times through the span of a single day.
During the cleaning activities, just over 240 yards of grit and debris were removed from the pump station with an additional 2,100 yards of debris removed from the interceptor lines. A total of more than 4.1 million lbs of grit/debris was cleared out. Once the debris had been removed, the wet well water levels had been properly adjusted to maintain the lower wet well levels. This allows for increased runtime for the sanitary sewer pump before combined sewer overflows (CSO) events occur. The interceptor is now flowing properly as it nears the pump station.
All of the work occurred exclusively during the daytime and under normal flow conditions. The daily dry weather flows were calculated at about 11 million gallons per day (mgd). During storm events, it could exceed 29 mgd while the peak hourly design flow at the plant is 27 mgd.
Since the project began in 2019, the majority of the work was completed during the middle of COVID-19 shutdowns, so many residents in the area were in their homes during the inspections and cleaning. The inspections generated a few questions, but the cleaning is where interactions occurred because of how much noise the cleaning process can generate. Once the residents were informed of the project scope and what the outcome would be, everyone was very welcoming to the end results of clean and properly functioning sewers. The residents in the area worked with the crew to get past the inconveniences to them once everyone was on the same page.
As a result, the drainage for the new housing development project is working properly with a higher velocity of water flow throughout the Alder Street interceptor. A decrease in sewer elevation has also been observed, decreasing the chances for surcharge and backups. Areas of major pipe rehabilitation were identified as well with the final planning stages underway. The surveying and design process will begin in the near future.