Planning for the Future: Assessing and Replacing Sanitary Sewer Infrastructure

If you have concerns about your city’s infrastructure, you are not alone.  However, being in good company isn’t helpful when it comes to the everyday challenges of managing expensive infrastructure and facilities for your utilities.

Sanitary sewer infrastructure doesn’t exist in isolation; it is a component of an entire system of conveyance and treatment. It is recommended that the system be reviewed in its entirety; however, today we’ll take a closer look at your collection system.

1.

 

Sanitary sewers are corrosive environments and need attention and maintenance. In fact, to protect your city, you must maintain your infrastructure. If you don’t, you could be held liable for property damage that is a result of broken pipes or sewer backups.

Whether you are a newly elected official or you have been in office for many years, the questions are the same: What do I have? What condition is it in? Is it repairable or must we remove and replace? What is our capacity to move wastewater – current and future?

SYMPTOMS

The symptoms are often obvious – surcharging, overflows, increased flows to your wastewater treatment plant, and citizens experiencing backups in basements. A positive sign that change may be necessary is growth – residential, industrial, or commercial; all will have an impact.

FINDING THE CAUSES, GATHERING THE DATA

Seek professional help to identify and solve the problem. Your engineer will assist in looking at the entire system. Developing a sanitary sewer system plan aids in future decision-making, provides a roadmap for economic development, and results in an efficient use of public money. The plan should address sanitary sewer overflows (SSO) and basement backups, help predict the impacts of change and growth, and identify the resulting burden to the system, the need for future service areas, and the costs for improvements.

2.

An engineer may take you through steps similar to the following:

  1. Community survey. To make good decisions, you must have good data. The survey will provide feedback on the symptoms experienced by your citizens. Your staff should be consulted because they are on the front line; that makes them a good source of information on breaks, overflows, and backups.
  2. Survey manholes, determine pipe size in/out of the manholes, and determine location and slope of the collection system lines. Any study starts with a good map – the better the map, the better the information collected, the better and more economical the solutions for the collection system.
  3. The process.
    • Using GPS and aerial base maps, map manholes and collection lines.
    • Inspect manholes; look for structural and leaking issues.
    • Televise the collection system. Determine condition, visually inspect for significant infiltration through pipe joints, and look for illicit connections – field tiles, roof drains. Look for blockages – root infestations, collapsing of the sewer, debris or sediment, or protrusions (poorly installed services, for example). Record condition of the lines on a map for future evaluation, along with type and size of pipe, joint type, wye location/size/condition, etc.
    • Flow monitoring. Data can be used to establish a relationship between rainfall amounts and timing of the rainfall in relation to when the system is overloaded and overflows. Use the data to identify problem areas in the system and the need for wastewater treatment plant expansion.
    • Smoke testing identifies cross connections and illicit connections to the sewer – storm sewers, roof drains, septic tanks, tiles, etc.
    • Modeling verifies sewer capacities and sizing. This can determine peak hour flow capacity, identify areas where additional capacity is needed, and help plan where to focus future development.
    • Existing city data may be reviewed: lift station or treatment plant data, population projections, current/projected development activity.
    • Note concerning the private collection system: there can be as much pipe, and therefore leakage, here as in the public’s collection system and needs to be addressed as well.

3.

Smoke testing

Smoke testing

PLANNING AND PRIORITIZING

With condition assessed, a work plan is developed, and costs can be determined in today’s dollars.  Priorities could include:

  • IDNR mandated work – primary focus is elimination of significant and cost-effective inflow and infiltration
  • Emergency repairs – blockages and health and safety issues
  • Critical repairs – work that can wait, but should be done in 2-5-10 year period
  • Regular maintenance – establish a regular maintenance and repair schedule for portions of the system that continue to degrade

FUNDING

Funding is a challenge; planning for these large expenditures is imperative.  According to the National League of Cities, these capital costs plus operations and maintenance for which localities also are responsible total about $60 billion annually for drinking water and wastewater systems.

CDBG, USDA, SRF, and bonding are all common funding sources. Cities also raise water and sewer rates to accommodate increases in operations and maintenance – a wise decision. Be sure to consult your registered municipal financial advisor.

A NOTE ABOUT MAINTENANCE

While condition and age are dominant factors in a city’s decision to replace sewer lines, regular maintenance is key to prolonging the life of your system. The life of pipes can often be extended by CIPP – cured-in-place piping but only if the pipe is salvageable. Removing roots, pressure cleaning, repairing joints, clearing stream crossings, removal and replacement of deteriorating pipe, recording backups and overflows are all helpful in the process. Combine these with regular updates to your system’s map and you are doing your part to increase the life and service of your sanitary collection system.

IN CLOSING

Keeping the big picture in mind is imperative when you are making fiscally sound long-range decisions for your community. Take the time to plan. Your citizens will benefit.

 

FOX Engineering is an environmental engineering firm based in Ames, Iowa. We specialize in water and wastewater solutions for our diverse municipal and industrial clients. Our work varies in size and scope and can be found throughout the Midwest and beyond.