Preparing Wastewater Systems for Major Storms

Changing weather patterns are leading to an increase in the number and intensity of major storms each year. For wastewater and stormwater systems, as well as the managers who oversee them, these weather events pose serious threats—threats for which some systems and municipalities aren’t prepared.

Heavy downpours, strong winds and powerful thunderstorms can lead to stormwater surges, power outages and unsafe outdoor working conditions. In turn, these can result in substantial environmental, health and safety hazards for the community. Here’s a look at the main risks to consider and tips for developing a storm preparedness plan that addresses them.

How storms impact wastewater systems

Major storms pose a variety of threats to wastewater and stormwater systems, including the ones below.

Overflows

For many wastewater systems, one of the most prominent threats is heavy rainfall that leads to overflows. A sanitary sewer overflow (SSO) allows raw sewage to be released outside of the system. In addition to contaminating waters and causing serious water quality problems, an SSO can cause back-ups into homes. This can lead to property damage and threaten public health.

When combined sewer systems are hit with more runoff than they can handle, a combined sewer overflow (CSO) occurs. Untreated stormwater and wastewater may enter nearby bodies of water, polluting the water and raising public health concerns.

Power outages

Backup generators are commonplace at pump stations and wastewater treatment plants, but losing power is still a major risk. Generators can provide power for only so long, and refueling them requires manpower that may be urgently needed for other tasks during a storm.

Facility or equipment damage

High winds and lightning strikes can damage buildings, machinery and more. Downed supervisory control and data acquisition systems and telemetry systems can blind operators to activity in the network, reducing their ability to quickly respond to problems.

Personnel safety and availability

When winds reach 40 mph, it’s no longer safe for anyone to be working outside. In the event of high winds, flooded roads or downed trees, personnel won’t be able to leave their location to set up pumps or repair damaged infrastructure until conditions improve. What’s more, new personnel can’t be called in to deal with mounting emergencies.

Creating a storm preparedness plan

It’s impossible to predict exactly how a storm will impact a wastewater or stormwater system, which is why municipalities and wastewater system managers need to develop a plan that covers all contingencies. An effective plan should include the critical steps described in this article.

1. Identify customers most at risk

Consider which customers will be most affected by a major storm. Identify not only which areas have the largest populations but also those that are the most vulnerable, such as low-elevation areas.

2. Assess the infrastructure

Determine the condition of the infrastructure throughout the system, particularly in the areas that are most at risk. If many of the pipes and pumps are less than 20 years old, they may be sturdy enough to weather the storm. Older infrastructure will be more vulnerable to potentially catastrophic damage, as will infrastructure that is already pushed to the limits of its capacity.

3. Plan for system failures

Design solutions to potential system failures and compile a bill of materials that would be needed to implement them. Estimate the number of pumps that may be required, as well as the diameter and lengths of pipes and fittings. It’s important to calculate the total dynamic head needed to move the water. That means accounting for flow rate, changes in elevation, distance and more.

4. Establish emergency procedures

Create a list of emergency procedures so employees know what to do when a major storm looms. The list might include specifics on whom to contact and when as events unfold, as well as preemptive safety measures to take, such as:

• Securing loose objects and equipment, including racks, excavation vehicles, containers and dumpsters;
• Bringing inside any items that can be stored indoors; and
• Lowering and securing stacks of materials that must be kept outdoors.

The case for investing in storm preparation

It’s hard to deny the importance of storm preparedness, but securing funds for emergencies that may or may not happen is often a challenge. Considering the potential economic impact of a failure to prepare may sway decisionmakers to make the investment.

For example, while storm preparation might cost in the neighborhood of $1 million per year, the cost of damage from a severe SSO or CSO can easily top $1 billion, even in small communities.

If the cost of cleanup and repair is covered by state and/or federal emergency funding, serious fallout could still result in the form of a loss of public trust. Preparing wastewater and stormwater systems for severe weather events can help leaders maintain the public’s confidence in their ability to keep their communities healthy and clean.

For wastewater removal equipment and help with planning needs, contact the United Rentals Fluid Solutions group.