A 40-year-old sewer pipe broke along Canal Street on May 28, spilling 105,000 gallons of sewage. At least one-third of the sewer pipes in the City of Myrtle Beach are between 30 and 40 years old, according to the city.
"I don't know that there's a guarantee that it wouldn't occur again," city spokesman Mark Kruea said. "This was a localized failure of a small section of pipe due to multiple issues. It's very rare. We may have one instance like this per year, if that."
According to city officials, the pipe that broke had been worn down from age and corrosive gases. That day, more sewage was flowing through the pipe, causing it to break.
Kruea said the city's public works department inspects the pipes using a camera to see if any repairs or maintenance need to be done. The tool also allows them to decide when pipes need to be replaced, regardless of age.
But in the case of the pipe along Canal Street crews did not catch the thinning walls. Kruea said the pipe that broke was a force main, meaning a pump helps sewage flow through the pipe. A camera cannot be used to check the quality of the pipe while force mains are in use.
"The pipe obviously was weak at that location," Kruea said. "You may not be able to see that in all instances."
Forty-year-old pipes aren't the oldest in the city. Pipes in Dunes Club and Dunes Lake were placed in 1969. Other areas in the city with pipes dated more than 40 years old are along Oak Street, along 79th Avenue North and leading to city hall.
In the city, pipes are made of cast iron, reinforced cement, ductile iron or PVC.
"Many factors must be taken into consideration when evaluating a pipe's life expectancy and the likelihood of failure," said Bobby Knight, water and sewer superintendent for the city. "A cast-iron pipe, for instance, has a life expectancy of 75 to 100 years under perfect conditions.
"We unfortunately rarely ever have perfect conditions. A sewer pipe works best when at full capacity. Our system is designed for summer flows and in our off-peak months, the pipes are less than full, providing for a more corrosive environment. Our goal is to analyze all of our assets and accurately."
Kruea did not seem concerned that older pipes in the city may break, saying, "It certainly can. That's why we maintain the system to make sure it's up to date. It's a corrosive environment."
With much of the construction done throughout the city since the late 90s, Kruea said a lot of the sewer system is about 20 years old.
"If it's done right, put in right, 30, 40 years is nothing. Most municipalities have problems with things that are 70, 80 years old," said Ed Carey, a construction management consultant.
"You've gotta remember 100 years ago it wasn't 10-foot, 20-foot sections of concrete pipe or some kind of plastic pipe," he said. "It was clay tile, it was almost like brick tunnels sometimes. Technology's a lot better."
Contracted workers are currently replacing lines in the Dunes Club area that were placed in 1969.
Kruea said crews contained most of the spill in May, and water quality samples were collected from several locations in Withers Swash by Coastal Carolina University.
On May 29, researchers collected samples from various points along the swash, testing the number of enterococcus bacteria in the water — a bacteria that lives in intestinal tracts of animals and people, according to the South Carolina Department of Health and Environmental Control.
The highest point tested registered about 18,400 bacteria per 100 milliliters at the corner of Canal Street and U.S. 501, the closest tested spot to the spill. If this bacteria reaches the ocean and exceeds a threshold of 104, a swim advisory is issued.
Farther downstream, the number of bacteria in the water decreased. The closest tested point to the ocean registered about 680 bacteria per 100 milliliters.
DHEC did not require a follow-up test because the break was caught quickly, and repairs were made on the same day, Kruea said.
How does the city maintain sewer pipes?
According to documents provided at the city's annual budget retreat, officials are renovating several sewer pump stations including Ocean Creek, Plantation Pointe, 82nd Avenue North and 5th Avenue South.
The renovations have cost the city nearly $3,350,000 so far, documents show.
This year, city officials have proposed spending $995,000 on the sewer project, which leaves money for emergency sewer projects and other projects.
"It's in the budget for every year," Kruea said. "It's in the capital improvement project every year."
Recently, workers replaced sewer pipes in the Pine Lakes neighborhood. Kruea said officials are focusing on the north end of the city, because the south end has newer facilities.
Kruea said the projects are paid for through water and sewer fees.
"To answer the question what's to prevent it, the city's maintenance efforts, the relining that we do, the replacements that we program into the system all are intended to keep our utility functioning and serving the public," Kruea said.