Posts

I&I Issues Solutions Header

Today’s I/I Infrastructure Challenges

/0 Comments/in , , , /by

As we discussed in the previous post in this series, the increasing failure of America’s aging infrastructure has forced municipalities of all sizes to deal with the problem. The challenge is to do so as quickly and cost-effectively as possible. In this post, we review a sampling of the ways our cities and towns are addressing the most visible and pressing element of this issue: inflow and infiltration (I/I).

As wastewater collection systems deteriorate, I/I pours in, overwhelming collection systems. Sanitary sewer overflows (SSOs) have become a huge issue. So much so, that the federal Environmental Protection Agency (EPA) has recognized that many cities need help dealing with this scourge.

Helpful I/I Resources

The Agency has created a Wastewater Collection System Toolbox. It is intended to guide municipalities to better inspect, maintain and replace their collection system components and help avoid overflows. A large part of this maintenance involves finding and eliminating sources of I/I.

Within the elements of this toolbox, the EPA:

  • encourages the use of newer technology such as GIS and other location-based information systems to survey, assess and track system condition
  • advocates thorough planning to manage ongoing maintenance work and improvement of system capacity (CMOM)
  • supports communication with end users of the infrastructure, about ways they can contribute to a healthy system

As part of a U.S. EPA initiative, “Water Infrastructure Outreach,” several new tools are posted here for downloading to help manage infrastructure renewal, including:

How Some Municipalities Are Handling I/I

Many municipalities in California have posted their Sewer System Management Plans online, which could serve as a starting place for others who don’t have the resources to reinvent the wheel. You can find them by using the search string “Sewer System Management Plans.”

Speaking of what municipalities are already doing, let’s look at some concrete strategies they’re using to deal with I/I:

Baltimore, Maryland entered a modified consent decree in October of 2017. The MCD requires the city to do some additional rehabilitation on top of that it performed under the initial consent decree of 2002. It has initiated a two-phase, four part program to address these requirements:

  • Expedited Reimbursement Program – This is for sewage backups caused by wet weather. The program offers up to $2,500 per dwelling unit, per event, for reasonable, documented clean-up and disinfection costs.
  • SSO Notifications – The city maintains a database of ongoing sanitary sewer overflow (SSO) reports. These are collected on a monthly basis and reported quarterly to the U.S. Environmental Protection Agency (EPA) and the Maryland Department of the Environment (MDE).
  • Clean Drain Campaign – This initiative from the city’s Department of Public Works raises the awareness of Baltimore residents about proper disposal practices for cooking fats, oils, grease, wet wipes, and other household waste. This is intended to reduce clogs in public sewer mains
  • Headworks Project – Keys to the project are a well to receive incoming sewage, and a series of very powerful pumps that will improve sewage flow. Essentially, it will act as a giant sump pump. This project at the Back River Wastewater Treatment Plant will cost about $430 million, and go into operation by the end of 2020. Construction will continue into 2021. Ultimately, it will eliminate more than 80 percent of the volume of sewage overflowing the city’s aged sanitary sewer system, and keep the streams, harbor, and Chesapeake Bay cleaner.

The city also holds annual public meetings to update all stakeholders on the project’s progress.

Portions of Chattanooga, Tennessee’s wastewater infrastructure system are reaching the end of their useful life. This is causing failures in the wastewater system, mostly during heavy rain events when wastewater system capacity is overwhelmed by a high volume of stormwater. This, many times, results in sanitary sewer overflows (SSOs).

The city has embarked on a multi-phase, multi-year project that includes major upgrades and revisions to several sections of the wastewater system. These include:

  • pipe rehabilitation
  • pump station improvements
  • upgrades to the Moccasin Bend Wastewater treatment plant
  • comprehensive operational audits

How We Can Help

If your municipality is currently facing similar challenges, TrioVision wants to help. We are proud to offer some of the most technologically advanced, hardest-working CCTV inspection equipment available for the televising and recording of underground structures. Call or click today to get in touch with one of our sales specialists who can get you what you need to keep your systems flowing below ground, where they belong.

Series Post 1 header

The I/I Issue: The Basics of Inflow and Infiltration

/0 Comments/in , , , /by

Welcome to the first in our I/I series! Because it’s a huge problem in wastewater management, our industry talks a lot about I/I, or inflow and infiltration. But not everyone knows the exact definitions of these terms. So let’s take a closer look at exactly what these things are.

I/I Defined

Inflow and infiltration are terms defined against the definition of sanitary wastewater flows. Those flows consist of wastewater from sanitary fixtures inside houses, places of business, and other buildings. Sanitary fixtures include toilets, lavatories, sinks, bathtubs, and showers. We can think of these flows as created to be intentionally conveyed through wastewater collection systems consisting of underground pipes laid beneath streets and rights-of-way to a wastewater treatment plant (WWTP).

I/I, on the other hand, are considered unintentional flows; i.e., they find their way into these sanitary collection systems, but they don’t belong there. Inflow and Infiltration water is referred to as “clear water,” though it may be dirty, to distinguish it from normal sanitary sewage water in the collection system.

Overflowing manhole imageInflow: The Renegade Stream

Inflow is stormwater runoff that enters sanitary sewer systems at direct connection points in these systems. Many sources may contribute to inflow, including:

  • manhole covers
  • footing/foundation drains
  • roof drains or leaders
  • downspouts
  • window well drains
  • exterior basement stairwells
  • driveway drains
  • sump pumps
  • streams and other waterways
  • cross-connection to a stormwater system
  • yard drains where urban features prevent surface runoff, and storm drains are not conveniently accessible or identifiable

Typically, these sources are, at least, improperly or, at worst, illegally connected to sanitary sewer systems. This happens either through direct connections, or discharge into sinks or tubs that are directly connected to the sewer system. This type of improper connection allows water from sources other than sanitary fixtures and drains to enter sanitary sewers. In a proper scenario, this clear water should be entering the stormwater sewer system, or be allowed to soak into the ground. It should never enter the sanitary sewer system.

Improper connections may be made in residential homes, businesses or public buildings. This can happen because the person hooking up the connection is not a professional plumber and doesn’t know any better, or it can happen because that person is trying to avoid the expense of having to do it properly.

Either way, such connections can and do contribute a significant amount of water to sanitary sewer systems. Why is this a problem? Because 8-inch sewer pipes can adequately move the domestic wastewater flow from up to 200 homes, but only eight sump pumps operating at full capacity—or six homes with downspouts connected to the sanitary sewer pipe—will overload the capacity of the same eight-inch sewer pipes. A single sump pump can contribute over 7,000 gallons of water to sanitary sewer systems in 24 hours. This is the equivalent of the average daily flow from 26 homes.

Peak flows caused by inflow may generate a foul flush of accumulated biofilm (a collection of microorganisms on the water’s surface) and sanitary solids, scoured from the perimeter of oversized sewers during peak flow turbulence.

Infiltration: The Sneaky Flow

Infiltration is groundwater that enters sanitary sewer systems through defects in the sanitary sewer pipes. These defects may include:

  • Leaky manhole joints and pipe penetrations
  • Defective mainline pipe joints
  • Defective or leaking house lateral connections to the mainline
  • Cracked or collapsed pipe or manholes
  • Damaged and broken sewer cleanouts

Old cracked brick pipe with tree roots intruding

These defects may be caused by:

  • age-related deterioration
  • loose joints from ground shifting, hydraulic or seismic loads
  • poor design or installation
  • maintenance errors or neglect
  • damage from differential ground movement, heavy vehicular traffic on roadways overhead, or careless construction practices in nearby trenches
  • tree or plant root penetration

These cracks or leaks provide a ready entryway for groundwater wherever sanitary sewer systems lie below water tables, or where soil above the pipes becomes saturated. Sewer pipes are often installed beneath creeks or streams, because these locations are naturally the lowest point in the area. It’s more expensive to install pipe systems beneath roadways, which would be the next easiest location.

Because of their close proximity to such waterways, these sewer pipes are especially susceptible to infiltration when they crack or break. It is not unheard of for them to drain entire streams into sanitary sewer systems.

A Lurking Menace

The average designed service life of most sewer pipes is about 20-50 years, depending on the type of material used in their manufacture. However, repairing and replacing them is an arduous and expensive process, leading many municipalities to kick that job down the road. As a result, America’s sanitary sewer system pipes, along with the lateral pipes attached to households and businesses, have often gone much longer without inspection or repair. As a result, they are likely to be cracked or damaged, inviting infiltration during the next rain event.

In our next post, we’ll examine why inflow and infiltration are a serious problem for American towns and cities.