Tag: sewer

EngineeringExpert WitnessWeather

Hurricane Floodwater & Wastewater: Sanitary Engineer Expert Witness Analysis

Five days after Hurricane Florence made landfall and pounded parts of the East Coast with winds and torrential rains, many areas are still inundated with flood water.

The floods have been devastating. Not only are the waters causing extreme property damage and personal injuries (in some instances death), they are also carrying contaminants and pollutants which have severe public health concerns.

Yesterday I read about some of the pollutants entering the floodwaters. Some of the items include: dead animals (turkeys, pigs, chickens), chemicals, manure, and untreated raw sewage. In fact, Bloomberg reported farm lagoons (storing feces and urine) had given way and sewer treatment plants have been overwhelmed by the rains.

Specifically, there are a variety of issues caused by these contaminants being washed away and transported via floodwaters. Bloomberg points out some of these concerns:

“Hog waste contains E. coli and bacteria, Rumpler said. Sewage overflows, combined with high floodwaters, bring the prospect of ecological impacts including fish kills. Humans coming into contact with fecal matter risk viruses, parasitic infections and rashes.”

So, there are some things our citizen brothers and sisters should avoid in North Carolina. Try to avoid swimming and wading through floodwaters. Remember the water is NOT just rain water. It is NOT clean. Those floodwaters include wastewater. Citizens should probably continue drinking bottled water until local authorities tell them otherwise.

That is enough of my non-expert suggestions. I’ve reached out to a sanitary engineering expert witness for some insights.

Sanitary Engineering Expert Witness Bonneau Dickson

Bonneau Dickson, PE, is a Sanitary Engineer with over 35 years of experience in all aspects of studying, designing, and constructing water, wastewater, and stormwater facilities, both in the United States and abroad. Mr. Dickson has designed approximately 300 water, wastewater, and stormwater projects. Has been resident engineer or otherwise participated in the construction phase of approximately 20 water and wastewater projects. Mr. Dickson has both project management and general management experience as project manager on approximately 175 projects.  You can learn more about his practice here: bonneaudickson.com.

Nick: With the post-Hurricane Florence flooding, we are reading about heavily polluted waters (pig excrement and raw sewage). What can North Carolina authorities do to address these sewage overflows and treat the wastewater?

Mr. Dickson: Very little. The pollution has escaped and there are few or no practical means of recapturing it.

The good news is that the torrential rains are likely to flush most of the pollution out to sea where it will decompose and be diluted down to insignificant concentrations.

Nick: At least one municipal sewer authority experienced catastrophic failure. Is there anything that can be done to limit or prevent such catastrophic failures when faced with heavy rains and severe flooding?

Mr. Dickson: Proper design of wastewater treatment facilities includes protection against flooding up to some level. Often, the protection includes levees and stormwater pumping facilities to prevent the wastewater treatment facilities from flooding.

The design storm often is a 100-year storm. I have not seen an analysis of the return period for a storm like Hurricane Florence but it could be on the order of a 500-year storm or a 1,000-year storm. Some areas were reported to have received up to 40-inches of rain in a few days. Typical annual rainfall in the Carolina’s is approximately 40-inches.

Nick: What are the major public health risks associated with untreated wastewater flooding parts of North Carolina?

Mr. Dickson: Probably diarrheal diseases from drinking or coming in contact with polluted water.

Nick: What can individuals and authorities do to limit public health risks associated with wastewater?

Mr. Dickson: Get the potable water systems operating again so people have clean water to drink and bathe in.


 

Until the floodwaters recede, please be safe. Listen to local authorities and remember to help your neighbors!