In the Storm's Wake
A guide to restoring water and wastewater services to a community following a natural disaster
When a natural disaster, such as a hurricane or a major flood, strikes, a typical first response is to evacuate quickly. Upon return and property review, the next priority is to find clean water to drink and use for washing and cleaning. The need for a functioning sanitary sewer system is of equal importance to bring a community back to normal functioning capacity. Communities also need to address safe disposal methods for wastewater generated from recovery efforts. These are just some of the many issues that have been brought to the fore because of the recent increase in natural disasters and flooding activities. This increase has prompted urban low-land communities with community water and sewer systems to incorporate more detailed water and wastewater restoration plans into their disaster-response efforts.
Central Water System Start-up Procedures
Central water systems are built in the ground away from view and constructed just under the frost line for most communities. This is a plus for starting up a system. After a disaster, it is likely that most, if not all, of the pipes will be full of water (potable or not) upon a restart of the system. When putting together a restoration plan, it is important to include the following key start-up procedures:
- Maintain communication with emergency coordinators, the public, and the state environmental agencies. Continue to issue "boil water" advisories until the system is fully functional;
- Make provisions to provide the public with an emergency source of drinkable water in areas where the systems do not have the ability to provide water;
- Inspect the water system's treatment and distribution facilities so that operators can assess immediate needs. Although it is not necessary to wait until all of the water recedes from the flooded areas, it is desirable. This step helps you seek out leaks or broken water lines from sink holes or wash-out areas left by the flooding. Although tenuous, your efforts may vary depending upon the size of your system and the accuracy of water maps. Yet, with experienced crews, you can achieve your objectives;
- Search out buildings or homes with heavy structural or foundational damage. Temporarily shut off water service from the street to avoid any further water damage due to broken pipes inside the structures. An organized program and good records are essential to this effort during and after the shut-off efforts;
- Once identified, quickly repair or isolate breaks until permanent repairs can be made to the facilities;
- Once the distribution system has been isolated and returned to working condition, rapidly flush the system. Your crews must take a fast-paced approach to their regular program of flushing and perform it as quickly as possible. Take grab samples from the flushing points and test them immediately. Levels of disinfection chemicals such as chlorine may have to be adjusted to higher than normal until the system is working properly. Maintain a chlorine residual level of 2.0 (milligrams per liter) mg/l or above in the flushed mains.
- Continue the program until operators feel comfortable that the distribution system is working adequately and safely. Obviously, a boil advisory needs to be in effect until the operators feel comfortable that the treatment and distribution systems are working properly.
The mechanical component of your system could involve more resources. Most water systems have booster stations and/or chemical feed facilities throughout the system. This is where you need to reach out to your pump maintenance companies and local electricians for some assistance. If the stations have not been flooded, stop and treat yourself with a coffee and perhaps a donut, and thank your lucky stars it was constructed above the flood plain. But, if your stations have been damaged by the floodwaters, they will most likely need a complete overhaul and cleaning.
In order to expedite system startup, temporary generators, motor controls, circuit breakers, and starters need to be acquired. These can generally be provided by electrical contractors or equipment rental companies. The electricians should conduct a complete examination of the power system feed, any backup generator power, and any supply panels. Everything that was under water has to be checked, including the items such as lights. Generally speaking, if a panel or power panel has been under water, it should be replaced. Motors may be saved, but they need to be sent out for baking prior to restart. You can prepare for these types of problems during system start up by having fast access to temporary motors and controls.
As for the pumps, generally the manufacturer can lend advice on damage, replacement, or other issues. Submerged pumps may require replacement or lubrication of the bearings, along with the motor work. As for the chemical feed systems, they require a complete cleaning, and the chemicals should be replaced.
As elevated storage tanks are generally near a high point in the system, they most likely will not be affected by flooding. However, they may need to be disinfected prior to use if the system integrity was compromised. At a minimum, a mechanical inspection, and an inspection from a structural engineer, should be scheduled sometime in the aftermath of the flood. The engineer's inspection should address any potential or existing damage to the foundation.
Last, but not least, is the water treatment plant. Unlike an elevated storage tank, water treatment plants are typically located in the lowest topographic areas of your system. They may be next to the river or stream, well points, or near small lakes at a low point. Unlike the distribution portion of the water scheme where areas can be isolated and cleaned, the treatment plant is usually in continuous operation. If the plant is flooded, first drop to one knee, look up to the sky and ask: "Why me?" Then, implement step two -- initiate your emergency procedures. Your entire operation and maintenance staff, along with outside contractors, may be required to put the plant back into operating condition. You and your staff will be tasked with taking your maintenance schedule shut-down and start-up procedure for each piece of equipment. You will need to piece it together into a master plan for cleaning and disinfecting the plant. And, with the help of your electrician, you will need to examine the entire electrical system. All tanks and mainlines need to be clean and disinfected. Government agencies generally understand that water is a top priority and will work with your system to provide all the necessary resources to assist you. Some caution needs to be used in the initial stages because chemicals (used for disinfection) that may have leaked from feed tanks could pose a health risk for employees and workers. This should be the first assessment made before any clean-up effort is conducted. It is wise to have a master plan in place prior to the disaster. Either way, you should anticipate a coordinated effort, along with many sleepless nights. Remember, delivering drinking water is serious business -- even under the best conditions, let alone with issues like recovering from a flooding condition.
Assuming you can get the treatment plant operating, the distribution system will follow with the procedures already discussed. If all goes as planned, your system should be operating in a few days to a few weeks.
Wastewater Treatment Issues
As for the wastewater treatment side of the problem, the collection system itself is designed to convey water and, in general, will drain as the floodwater recedes. Operators should inspect the system for obvious problems that may be caused by debris-clogged pipes or structures dislodged by the floodwaters. The pumping stations in the system will generally be knocked out by the floodwaters if they were not designed to function in the 100-year flood (although many floods exceed this level). The method of getting the stations up and running again are very similar to the water booster station methods outlined above.
Wastewater treatment plants are situated at a low point next to a stream or river for discharge purposes. And they will experience many of the same problems water plants. One problem operators may face is that, in all likelihood, the biology in the plant was upset with the flooding, and it washed out of the treatment tanks because of the high flow. This will necessitate reseeding the biological process.
This article originally appeared in the 03/01/2006 issue of Environmental Protection.
Michael R. Filmyer, PE, LO is a senior project manager with BCM Engineers, a division of ATC Associates Inc. ( www.atcassociates.com). His specialty is the design and construction of water and wastewater facilities. He has more than 19 years of experience with sanitary, mechanical, civil, and environmental engineering tasks associates with large infrastructure projects throughout the United States. He can be contacted at (610) 313-3100.