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

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.

Gearing Up for Year-End, Part 2: Budgeting and Equipment Acquisition

With year-end planning in full swing, one of the inescapable must-dos is budgeting for the next year’s projects. In wastewater and stormwater management, this means including pipeline inspection as a line item.

Many municipalities are under consent decrees to lessen or put an end to non-point source pollution, and this necessarily has a massive impact on budgets. While normal budgets are determined by tax revenues, consent decree work budgets are driven by what kind of mandates they have issued. Depending on the specific project, sometimes the federal government will help cities find funding to do what they need to do.

  • If there is a “green” aspect to your project, you may decide to seek funding from an EPA Clean Water Act Nonpoint Source Grant (Section 319 Grants – https://www.epa.gov/nps/319-grant-program-states-and-territories)—Congress amended the Clean Water Act in 1987 to establish EPA’s Section 319 Nonpoint Source Management Program to provide greater federal leadership in focusing state and local nonpoint source efforts. Under Section 319, states, territories, and Indian tribes receive grant money to support a wide variety of activities, including:
    • technical and financial assistance,
    • education and training,
    • technology transfer,
    • demonstration projects, and
    • monitoring to assess the success of projects implemented under the grant.
  • EPA Clean Water State Revolving Fund (CWSRF – https://www.epa.gov/cwsrf)— This program is a federal-state partnership that provides communities a permanent, independent source of low-cost financing for a wide range of water quality infrastructure projects:
    • wastewater treatment
    • stormwater management
    • nonpoint source pollution control
    • watershed and estuary management.
  • Often there are National Pollutant Discharge Elimination (NPDES – https://www.epa.gov/npdes/municipal-sources-resources) funds available, although the research and paperwork can be formidable.
  • You may need to be creative in your approach and the way you view your project, when it comes to identifying potential funding sources. Consider asking your local water district for help. Or you may choose to create your project in such a way that it qualifies for funding from other, less obvious sources.

Equipment Field Demonstrations

If pipeline inspection equipment is on your list of must-buys, first do as much due diligence as possible. Research every possibility online to keep your costs in time and travel to a minimum. You may want to consult our exhaustive Due Diligence series in this blog, starting with the first post (https://www.trio-vision.com/pipeline-inspection-equipment-considerations-what-you-dont-know-can-hurt-you/) and reading through to the end.

One of the important steps in choosing the right equipment for your needs is scheduling a field demonstration, so you can see exactly how it behaves in actual use. Don’t settle for a simple show-and-tell from a sales representative, especially if it’s new equipment you’re not familiar with. You don’t want to see how it performs under optimal conditions, which rarely exist in the field. You want to see how it handles the rigors and unexpected turns of a real job.

Once you’ve scheduled your demonstration, what should you expect?

According to Robert Studdard, our Southeast Regional Sales Manager, “A true demo should consist of an actual pipe inspection in normal working conditions. The pipe should be cleaned prior to inspection. The pipe size being worked on should be known in advance, so the crawler can be properly set up”, he says. “And the customer should understand that there are no ‘bulletproof’ systems on the market: meaning that the condition of the pipe, its lack of maintenance, and other factors can and will affect the way the inspection goes.”

All of these real-world possibilities should be explained by the sales rep, and the customer should be wary of too many promises made with no limitations. In other words, if it sounds too good to be true, it probably is.

The need for realistic expectations extends to the length of the inspection distance coverage. Most manufacturers claim that their equipment will go a thousand feet, and it will. However, just because you can doesn’t mean you should. Most municipalities and counties go manhole to manhole, somewhere between 300-500 feet per run. So make sure you actually need that run length: Bells and whistles on equipment increase its cost, and you don’t want to pay for something you simply don’t need and probably will never use.

You may also wonder what questions you should ask to complete an accurate and in-depth comparison of all potential equipment solutions. We have created a convenient, downloadable checklist for you to use in making these comparisons. It provides a one-stop, go-to document to allow you to ask all the important questions of each manufacturer or rep, so you can then compare apples to apples, so to speak.

Gearing Up for Year-End, Part 1: CIP Planning

While many folks are shifting into late-summer/early fall activities such as back-to-school and looking forward to the start of football season, municipal public works and storm & wastewater management officials have other things on their minds.

 

These professionals, whose performance over the next year may determine a great deal about the physical health, safety and comfort of those in their service areas, are thinking ahead to the year’s end. This time is always fraught with the pressures of making the best decisions for their systems and constituents, when it comes to planning the next year’s projects, expenditures and acquisitions.

 

It’s All About The Data

Much of this decision-making takes place only after analysis of earlier collection system pipe inspection results. Depending on the severity of what’s going on in any given pipeline, they may create up to a ten-year plan for their system segments most in need. To make sound, evidence-based decisions, they need to have solid, accurate data about real conditions from their inspection programs.

 

Knowing how best to allocate their always-limited resources requires accurate PACP coding of defects and rich, thorough data about every facet of their underground assets. This knowledge is critical to enabling city managers to adequately fund time-critical rehabilitation work, while nipping any growing problems in the bud, while they’re still relatively inexpensive and manageable.

 

The way many larger cities handle these inspection and rehab tasks is with their own dedicated crews. The work of those crews will directly reflect the value of the pipeline inspection equipment and data collection, analysis and reporting software they use.

 

Establishing Parameters

The first step in figuring out a budget is asking the right questions about the current situation and laying out specific time-and-budget-oriented goals. These questions will establish the figures needed to estimate time and cost. They include, but may not be limited to:

  • How much work needs to be done, and what kind of work?
  • How old are the lines and when was the last time maintenance was done?
  • What is the existing capacity of involved system segments? Do they need to be upgraded?
  • Have there been SSOs recently, or in the past?
  • Are you operating under a consent decree? If so, it will mandate what you must get done each year. This may force your hand in hiring more staff, more area contractors, and/or buying new equipment to meet those quotas.

 

Bringing Home the Data

In data collection, it’s important that the municipality be able to import any reports generated during inspections for the city. This way, you can send it off to the federal government to show progress on the work required by any consent decree.

 

You want to avoid “data islands” — where you have data in two or more different software packages, but your programs can’t talk to each other. It’s critical that engineers be able to access all inspection report data at once. This helps them decide where their budgets will work hardest. Make sure all your data management tools have the ability to share data about the overall health of your entire system.

 

One important aspect of data management that too often gets neglected until there’s a disaster is data backup. It’s critical to back up all the data you generate, both text and imagery, during your inspections. If not, you may end up having to do them over, and no one has the budget to cover such needless duplication of effort. Instead, contact your system administrator from the get-go and discuss your backup needs, so together you can find

 

Budgeting

Budgeting can become a little complicated for cities under a consent decree. You may want to take a look at the amount of work you must do to meet its requirements, on top of servicing your usual maintenance program. Obviously, this puts added stress on funding sources. In our next post, we’ll take a look at the many sources you might consult to look for additional funding to supplement your regular maintenance budget.

Manufacturer Considerations, Part 1: Choose Your Partners Well.

When you take on the purchasing role in your company, with each buying choice you must decide whether the purchase warrants a short-term or long-term stance: are you just choosing a vendor, or a partner in your success?

With consumable items such as office or cleaning supplies, you can basically view them as commodities, which allows you to buy more on price and availability; in other words, a short-term stance that lets you be flexible according to immediate needs. With big-ticket items such as durable equipment, however, only a long-term buying stance will serve you well.

Such huge capital expenditures will either help or haunt you for years over the course of their service lives, depending on the due diligence you did to determine whether these purchases would wind up as expenses or investments on your bottom line. That’s why you need to think about more than just the equipment itself. You need to consider the vendor you’re getting it from.

There are quite a few questions you need to ask yourself about this company you could be associating with for quite some time. After all, you’re hoping the equipment has a long and healthy life, and you’ll likely be working with its manufacturer and/or distributor for the length of that life.

Vendor or Partner? Important Questions

Will the manufacturer be more than just a vendor? Will they take a consultative approach to sales and service, functioning as a full partner in your success? In other words: Whose needs come first—yours, or those of the vendor? In researching the company, there are several other questions you can ask to help you answer these.

Who owns the company? Is it privately held by a small group or family that values the company for what it really is and does; or is it simply another “property” in some big holding company’s portfolio, vulnerable to being sold off or broken up at the whims of a profit manager? The answer to this question largely determines how your company will ultimately be treated by the equipment seller. Respect for staff and company values starts at the top, and extends to the customer…or it doesn’t.

Who in the company will you be dealing with, and are they the real decision-makers? Do they have the authority and power to truly satisfy your requests? Again, this knowledge is crucial, because small business or family-run structure is far more flexible and less formal, allowing for the idiosyncrasies of new or long-established relationships, rather than being forced into some rigid corporate structure. You, the client, will always feel the upshot of that policy.

How long has the potential vendor been in the marketplace? Are they newcomers to our industry, or do they have a track record of quality, performance and innovation? What’s their corporate culture concerning service and after-sales support? When you’re considering equipment that gets beaten up as badly as most pipeline inspection systems do, that last question will have a considerable bearing on your overall happiness with your purchase in the long run.

Time Well Spent

This is where due diligence can get a little time-consuming, but it’s time well-invested to protect one of the largest spends you’ll ever make in your work. Good references are important, but don’t just stop at the “happy customer” testimonials the company offers. Seek out and ask colleagues who are or have been their customers, for real-world opinions.

Go to industry shows and ask around. Participate in online forums offered by our industry’s trade publications, where you’ll find plenty of your colleagues willing to speak out. And don’t forget social media: Lots of contractors and municipal representatives spend time on Facebook and LinkedIn. Join them, and ask about their experience with, and for honest feedback about, the vendor you’re considering.

This is just the beginning of the homework you should be doing on companies you’re considering entering into a significant relationship with. Next month, we’ll explore Manufacturer Considerations, Part 2, in this ongoing Due Diligence series.