Grand Haven Spring Lake Sewer Authority

Wastewater Forcemain Leak

 
Background
A 12-in.diameter, ductile iron pipe forcemain carries wastewater pumped under the Grand River from Spring Lake Township, Spring Lake Village and Ferrysburg to the wastewater treatment plant in Grand Haven. It carries an average of 1.25 million gallons of wastewater a day (mgd). It operates at a maximum internal pressure of about 70 pounds per square inch (psi). It is buried underwater about three feet below the river bottom. It is 3,400 feet long from bank to bank. It was built in 1972, 45 years ago. The pipe is specially designed to cross under rivers. It is the heaviest-duty class of ductile iron pipe made.
Late in the afternoon on Sunday February 26, a resident reported seeing water bubbling up and breaking the water surface in the middle of the Grand River. Because flow into the treatment plant is lower on weekends, it was difficult to locate the flow bubble in the river until flow increased. Early Monday morning February 27, wastewater flow under the river picked up and the leak location was apparent from shore.

Repair Timeline
The Grand Haven Spring Lake Sewer Authority began the process of repairing the leak at 8:15 AM on Monday, February 27.  Divers from the King Company, a marine contractor from Holland, inspected the leak location late in the day on Monday, February 27. The diver reported a 2-inch-diameter hole near the top of the pipe. This is consistent with Prein&Newhof's calculations based on a 500,000 gallons per day (gpd) leak.
A similar leak occurred on this forcemain in 1998. Field notes from that leak say it may have been caused by damage to the pipe exterior from a working barge's support studs. This leak and the 1998 leak occurred in different locations.   The dive crew ran out of daylight on Monday, and it was decided to start the repair on 7 AM Tuesday morning, February 28. This also provided an opportunity to have Plumbers Environmental standing by with 5 - 10,000 gallon tanker trucks.  The trucks were available to pump down the underground effluent storage.  This ensured that we could keep the pumping stations disconnected during the underwater repairs.  The dive boat went out at 7 AM, and the repair was finished at 9:15 AM Tuesday. The hole was repaired using a stainless steel clamp/sleeve with a rubber gasket, the same repair method and material used by public works staff when a watermain breaks.



Q & A:

Why did this pipe leak occurThere was a hole in the pipe and we do not know the cause

What are you doing to learn why this pipe leaked?
We took soil samples from around the pipe and we will test it to see if it is corrosive to ductile iron.
We are looking at additional ways to learn more about this pipeline's condition, in ascending order of complexity and cost:
  1. 1.       Using a portable dam, we may isolate an area around the repair and inspect its exterior for signs of damage or exterior corrosion.
  2. 2.       There is leak detection technology available which can tell us if there are smaller leaks in the pipeline.
  3. 3.       There is leak detection technology available which measures a metal pipe's wall thickness over its entire length.
What will it cost to learn more about this pipe's condition?
The engineering firm Prein & Newhof is working to check the feasibility of the above methods and develop cost estimates for each of them.

What did it cost to fix this leak?
It is too early to know the exact cost. We expect it may be between $50,000 and $90,000.

How much wastewater leaked out of this pipe?
We believe just under 2,000,000 gallons leaked into the river. To put this in perspective, on Monday February 27, the Grand River's flow rate was 9,200 cubic feet per second. The wastewater leak contributed about 0.777 cubic feet per second to the river's flow. This is less than one thousandth of the total river flow.

What are you doing so this does not happen again?
We have been saving money and planning for several years to build a new forcemain pipe across the Grand River. This break may accelerate that process. We estimate the cost of building a new forcemain is as much as $5,000,000 and it involves three communities.  A large project like this takes time to design, finance, and build.  Otherwise, we will continue to explore the investigative options described above.
Although we believe we carried out a swift response to this leak, we will debrief with our entire response team.   A full report will be prepared for the Boards of the communities served.

For additional information Contact:
Craig Bessinger - Chairman GH/SL Sewer Authority  
       (616) 842-5803
Jim Hegarty - Prein & Newhof Engineering                     
       (616) 485-0269




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