GRANITE CITY SAVES BIG BUCKS
THROUGH HIGH TECH SEWER
REPLACEMENT

By BRETT L. HANKE, P.E.
Alderman, Granite City

For several years the City of Granite City, Illinois, had suffered from numerous sewer failures and the appurtenant infiltration and grit problems normally associated therewith. In 1985 newly elected mayor Cruse commissioned Horner and Shifrin, Inc. to perform a study of the problem. After several months of research, the study was completed. It identified over ten million dollars in remedial work of which about half was sewer replacement.

The recommended method of sewer replacement was a relatively new "high technology" method called "Insituform" which is Latin for "formed in place". That is exactly what the process does. It builds a new sewer line inside of the old one.

In Granite City the recommendations of the sewer repair study began to be implemented in 1986. As recommended, the sewers with the highest potential for collapse were addressed first. These had been identified from television videos taken by the city street department. They were also those which almost always were below the relatively high water table. In all, over 4,600 lineal feet of sewer have been insituformed at a total cost of approximately $370,000.

The obvious question which the reader may ask is, "Why not just dig the sewers up and relay them with PVC pipe?" Granite City lies in the Mississippi River valley. The soils are basically sand to a depth of about 100 feet. The water table in the area is determined by the water level in the Mississippi and is invariably above the sewers in certain areas. Excavations below the water table are almost impossible without dewatering. The cost of installing dewatering wells is excessive as also is the cost of running the pumps. Also, several of the sewers run under streets, buildings or other inaccessible areas. Insituform can be placed anywhere the sewer has not completely collapsed, thus making it a much less expensive alternative.

Where sewers had collapsed, some 22 locations remained unrepaired as of 1986, the sewers had to be excavated and the street department make a "point repair". This usually required dewatering. Normally, the engineering department has had Insituform, Inc. reline the adjacent sewers in order to stabilize them and prevent another break further down the line.

In some cases, the Granite City sewer problem is

How Insituform Is Installed

FIGURE 1. A special needled felt reconstruction tube, Insitutube, with a PU or PVC coating on the outside is custom engineered and manufactured to fit the damaged pipe. It is impregnated with a liquid thermosetting resin and lowered into a manhole through an inversion tube. One end of the Insitutube is firmly banded to the lower end of the inversion tube elbow. FIGURE 2. The inversion tube is then filled with water. The weight of the water inverts the Insitutube into the damaged pipe, turning it inside out and pressing the resin-impregnated side firmly against the inside walls of the old pipe. The smooth, coated side of the Insitutube becomes the new interior surface of the pipe.

FIGURE 3. After the Insitutube is inverted through the old pipe to the desired length, the water used for inversion is circulated through a boiler. The hot water causes the thermosetting resin to cure within a few hours, changing the pliable Insitutube into a hard, structurally sound, pipe-within-a-pipe, Insitupipe ™. It has no joints or seams and is as strong as or stronger than the pipe it replaced. The ends are cut off and the inversion tube and scaffolding are removed. Normally, there are no messy excavation repairs to be made since most work is done without digging or disruption.

December 1988 / Illinois Municipal Review / Page 7

somewhat unique but not atypical for the sandy soils normal to river bottoms or shorelines. The Granite City area is very flat. This necessitates relatively deep sewers in areas. These sewers were constructed in the 1950s of clay tile, bell and spigot pipe with tar sealed, oakum joints. The saturated sand soil shifted slightly over the years and a small leak would occur. As water leaked in, it washed in the fine sandy soil creating a void under or around the pipe. Over several years, the void would grow until further movement of the pipe created a bigger leak and aggravated the problem. In some cases, major misalignment has occurred, in others complete collapse. Insituform not only stops the leak and reinforces the pipe, but it can transverse a misaligned pipe as long as it is not completely collapsed.

Additional benefits of Insituform include no mess on the job site, a key political concern. Residents have been very pleased with the results, whereas whenever open excavation has been needed, residents are invariably upset about lawn damage and foundation settlement. The savings in lawn restoration add to the cost effectiveness of Insituform. Because house connections can be cut out the same or next day as the repair is made, residents are minimally inconvenienced.

In all, Granite City has found Insituform to be a great boon to the solution of sewer problems. To date, it is estimated that over $630,000 has been saved compared with projected conventional sewer replacement costs. It has enabled the city to solve the sewer leakage/failure problem from within the confines of its annual budget without borrowing. Some funds have been allocated by the state from the "Build Illinois" program. However, the lion's share has come from individual taxes, which have decreased in each of the three program years. Insituform has turned out to be the one politically acceptable means for a cost effective solution to this engineering problem. •

Page 8 / Illinois Municipal Review / December 1988