This past February residents living near OPRF High School began to notice a corner of the intersection at Erie and Scoville was beginning to collapse. This was not a super sized pothole but a fast expanding sink hole.
Upon investigation the Public Works Department and Engineering Department determined a corner “bulkhead” in the eight foot diameter relief drain, located 30 feet below the street, had collapsed.
The engineering detectives determined that when the relief drain began to fill up with storm water, the storm water would leak out from the damaged section of the drain and loosen the earth around the drain. Once loose, the earth above the relief drain began to collapse into the relief drain. After some time, the street intersection began to give way as the earth below the street began to fill into the damaged section of the relief drain.
A “bulkhead” on the north side of the relief drain, which runs east-west under Erie street, had failed. The bulkhead was designed to be ready to accept a larger north-south neighborhood relief drain connection if it ever became necessary. The “bulkhead plug” so to speak, is what failed.
This damaged section of the vast underground network of drainage pipes the village maintains was built as part of the $7.5 million, 1967 Sewer Relief Project. This project expanded drainage capacity in the Oak Park system. The combined sewage system takes our sanitary sewage and polluted rainwater away to be cleansed at the largest sewage treatment plant in the country.
Partial view of the Stickney Water Reclamation Plant
All our sewage is sent to the Metropolitan Water Reclamation District of Greater Chicago’s (MWRD) Water Reclamation Plant in Stickney. It is the largest wastewater treatment plant in the world. Oak Park’s 2011 wastewater treatment charges are expected to be approximately $4.8 million and paid through an MWRD property tax formula.
The 14 mile addition to our drainage system, built in 1968-70, makes up about 8% of our drainage system and is now 43 years old, almost middle age in drainage pipe life years.
The failing section of the drain needed to be fixed promptly. The problem with excavating from above and creating a shaft to repair the bulkhead from the outside, besides the drain being 30 feet deep, is that three utility lines that run near the relief drain would also have to be temporarily relocated.
Because this section of the relief drain is quite large, over seven feet in diameter, engineers and experienced contractors felt the repairs could be made from within the drain by sending crews in to clean out the drain and rebuild the failed bulkhead from the inside out.
Engineering bid the job both ways, fixing from inside or outside. Of the 13 companies that expressed an interest in the job, four submitted bids. Bids ranged from the lowest responsible bid of $165,000 (no dig option –repair from the inside) by the Cerniglia Company, to $422,750 by Kenny Construction for the open cut repair option.
Although the board awarded the project to the low bidder with staff’s recommendation, I still thought $165,000 sounded like a lot to repair a relatively small section of a relief drain. I asked Engineering to arrange for me to be able to inspect the relief drain and the damaged section and see for myself the conditions underground.
My adventure into the underground began with a big surprise. I thought there would be a ladder built into the manhole to descend into the relief drain. Nope.
My escort from Cerniglia, Louie Napolitano Jr., and I had to be lowered into the relief drain with cables and a harness. The depth, the pitch black dark, the running water around my feet, the smell, not a problem. Being lowered 30 + feet, dangling by a cable, not seeing where the bottom could be, well that was just a tad bit disconcerting. What if the cable snapped or harness broke? What if Louie or I dropped like bullets down the long narrow manhole? Scary thoughts of a control freak?
Once we got down and organized in the tunnel with our flashlights, navigating the slippery conditions in a few inches of running water, the poured in place intersection drain and extended drain sections looked in decent shape. But signs of chips decay and future vulnerabilities were able to be located every ten feet or so in my mini inspection. While we only managed to look at 30 or 40 feet of the 100 + miles of our drainage system, I’m feeling fairly confidant we should get another 60 years use or more from the 1968 built additions to the system if we continue to apply best practices to the inspections, maintenance and repair of the system.
The repair job is not quite half done but most of the debris that had fallen into the relief valve has been sucked out from above. Over the next couple of weeks the temporary bulkhead repair will be removed as the permanent repairs are made. We will inspect the repairs carefully and I will post a photo of the repairs for the civil engineers amongst us who may be interested in such an obscure part of our community lives.
As a result of today’s underground adventure I have a couple of observations and a suggestion.
First, the unheralded men who do this type of construction work certainly deserve our respect, appreciation, and decent pay. These are challenging and dangerous jobs requiring care, caution, strength and no fear of confined spaces.
Second, much of our country’s aging infrastructure will be hitting that 100 year old plus mark and we really should be setting aside local, state, and national funding to repair and replace our aging infrastructure in a timely fashion. Timely inspections, repairs and replacement of our aging infrastructure, our economic and environmental backbone, will actually save taxpayers money. Just look at how much one relatively small hole, in one 43 year old relief drain costs to fix! (Sidebar-the unexpected $165,000 necessary to repair this collapse will likely result in defering $165,000 of other planned sewer maintenance/repair work scheduled for 2011.)
Conclusion and Recommendation: Mainstreet to Washington DC – lets figure out a way to end wars and spend our resources to fix up our own infrastructure!
Thanks to Village Engineers Jim Budrick and Bill McKenna, as well as Louie Napolitano Jr. and Albert Conforti from Cerniglia Underground Construction, for making my trip to and back from the underground possible. I’ll lay off the pasta Albert just in case there is a next trip to the true underworld.
PS. No I did not see any rats!