Stormwater Archives - Infrastructure Digest

Largo to spend $37M on sewer upgrades

“The big driver is (that) it’s going to stop the overflows,” city engineer Leland Dicus said.

The sewer improvements are the result of problems that started about 15 years ago when the system overflowed during the heavy rains of that hurricane season, Dicus said. The overflow came out through manhole covers and dumped sewage in the street that eventually made its way to the bay. In all, Dicus said, about 30 million gallons of overflow came out of the system.

Why should you read this? Just the numbers: “$37M”, “30 million gallons of overflow.” Tampa Bay Times, January 2015

Using Grout to Stop I/I

The Village of Ashley project resulted in the Central Ohio Wastewater Services crews in finding significant I/I at the manholes. Crews found 17 manholes next to a creek in the woods that were 16 to 26 ft deep with a very high water table. In looking into the cost for replacement for all the manholes, the cost totaled approximately $300,000.

“The Village of Ashley did a (cured-in-place pipe) CIPP liner project in 2007, removing half the peak flow from 1 million gal/day to 500,000 gal/day at a plant that was designed for 190,000 gal/day,” Howard explains. “We found the infiltration was coming between the CIPP liner and the original pipe releasing at the manholes. The acting engineer at the time had heard of Source One Environmental (S1E) LLC and its product so we gave it a try. Since the start of the project, our average dry time flows have went from 60,000 gal/day to 30,000 gal/day and heavy rain fall events have fallen from 500,000 gal/day to 250,000 gal/day making the plant more efficient.”

Why should you read this? The effectiveness and precise role of chemical grouting is too little understood by sewer network managers, IMNSHO. Trenchless Technology, November 2014

Storm, Floodplain Work Offer Surveyors Some Great Opportunities

While floodplain preparation and addressing issues created by storms and floods are not the most pleasant topics for those in harm’s way, they can open up opportunities for land surveyors. Prep work, mapping and recovery efforts in the aftermath of major storms all open the door to the skillsets possessed by the professional surveying community.

Why should you read this? It’s not a disaster, it’s a business opportunity. POB, January 2015

City of Columbus, Ohio, Designs ‘Blueprint’ to Control Overflows

However, as the City began to enter subsequent phases of the tunnel program that focuses on controlling separate sanitary overflows, it decided to take a different tack. Rather than continue to build out the tunnel program, the City decided to address the cause of the overflows rather than the symptoms by refocusing its efforts on eliminating inflow-and-infiltration (I/I) through a comprehensive rehabilitation program and green infrastructure improvements. City officials believe that this approach — dubbed Blueprint Columbus — will achieve greater water quality benefits in a manner that will offer economic and social advantages that will benefit the City for generations to come.  

Why should you read this? Everyone loves a good I&I reduction story… Trenchless Technology, November 2014

KS Associates Takes 3D Laser Scanner Underground to Help NEORSD Abate Combined Sewer Overflows to Lake Erie

The goal of this project was to replace a fatigued inflatable dam in the 96-inch sewer that collects combined sewer flow from northwest Cleveland. The inflatable dam is an important mechanism that stores upstream combined sewer flow, reducing CSO discharges in the collection system before the flow is transported to a nearby wastewater treatment plant. NEORSD decided to remove the inflatable dam and replace it with a more efficient hydraulic sluice gate. The District hired URS Corporation to perform design services.

Laser scanning offered several benefits over conventional surveying methods. According to Mark A. Yeager, P.S., KS Associates Director of Surveying Services, “For safety reasons, surveyors could only enter the sewer during dry weather flows. Once we had our window of opportunity, accessing an active sewer five stories below ground posed safety challenges and required specialized confined-space procedures. Our priority was to measure the entire junction chamber and obtain the geometry that URS needed in as little time as possible. Using 3D laser scanning, we successfully gathered all the data and more — in one trip. Manually obtaining these details would have required more time at the project site and would have been more physically challenging.”

Why should you read this? As laser scanning becomes less ‘gee-whiz’ and more ‘ho-hum’, more and more uses are becoming obvious. Might your sewer network benefit from some scanning? Informed Infrastructure, September 2014

Innovation And Proactivity Put The City Of Evanston Ahead Of The Storm

“Evanston, Ill., has launched a three-pronged attack on stormwater overflows, but the increasing frequency and intensity of rain events is making the task more challenging.

Plagued for years with flooded basements and customer complaints, the utility has built a new system of stormwater relief sewers, added several new storm sewers, and installed flow restrictors which prevent storm drain overloads by forcing stormwater to pass down the street or alleyway to larger drains.

And while the system works well, Utilities Director Dave Stoneback says the heavier rainfalls the city has experienced in recent years can still cause flooding problems, especially in winter.”

Why should you read this? If you manage sewer networks, it’s always nice to learn how others are doing it. Municipal Sewer & Water, December 2014

Cost-effective off-road I&I reduction Two-pronged approach to manhole renewal eases pressure on sewer network.

The department produced an internal paper on the subject: Surface Water Inflow through Manhole Lift/Vent Holes into Sanitary Sewer Systems. They found:

  • When a cover is submerged, the lift/vent holes first perform as a weir and then as an orifice, allowing extraneous flows to enter into the manhole. As the depth of submergence increases, the inflow into the manhole increases.
  • When submerged by 2 inches, a cover with four .98-inch-diameter lift/vent holes may allow 15.8 gallons per minute (gpm) to enter. At 5.9 inches, 26.4 gpm may enter.

Note that this is the inflow only through the lift/holes. Additional inflow occurs between the steel cover and the steel grate, and between the steel grate and the concrete manhole.

Why should you read this? Are you a sewer or water network manager looking for a relatively cheap way to mitigate I&I? Then this is your article. (full disclosure: I wrote this article in my other role as an infrastructure writer. Which means it is especially awesome.) Public Works, February 2014

CSO Facility Replaces Obsolete Control Systems

“Each combined sewer overflow facility differs somewhat in size and design, but all basically apply the same treatment process: retaining the overflow, mechanically screening out solids, and disinfecting the water with sodium hypochlorite (bleach). Basins also have equipment that operators use to monitor flow rate and volume, collect samples, remove residual water from the basins, and clean them after a wet-weather event.

Despite their similar functions, the basins’ process control instruments vary widely. That’s partly because the basins were constructed over the course of the last three decades at a time when automated control technology was quickly evolving. The comparatively slow pace of public works projects was also an issue. From concept to commissioning, each basin required several years to complete because of strict municipal codes requiring public planning, open bidding and official oversight. Meanwhile, federal and state water quality standards were becoming more stringent, adding another layer of complexity.”

Why should you read this? Starting 25 years ago, Detroit made a big commitment to combined sewer overflow (CSO) facilities, and if urban stormwater is part of your life, their experience may be interesting to you.

Military Precision

“In March, work crews installed 41 flow monitors throughout the fort’s sewer collection system to identify leaks in the 91.2 miles of main sewer line serving the U.S. Army Base… It’s all part of a $2 million Sanitary Sewer Evaluation Study (SSES) under way at Fort Knox.” Good look at I&I program at Fort Knox, including the world famous ‘sewers o’ gold.’ MSW August 2012

Miami-Dade Water and Sewer Department

“The net result is that with the additional treatment level, it makes the water useful for a variety of reuse options, and so instead of disposing of the water, we will eventually be sending it down to Florida Power and Light” Nice overview of a big department facing tough challenges. For one thing, they’re dealing with hundreds of miles of failing pre-stressed concrete pipe. Energy &  Infrastructure, July 2012

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