C.A.C. served as a subcontractor for VRH Construction to complete the installation of approximately 500 LF of a 90’’ RCP sewer pipe as well as the construction of four poured in place chambers at JFK International Airport.

 

Before excavation, 145 16’’ diameter CFA piles were drilled from grade for the new sewer to be set on due to ground instability. Each pipe segment was 8 ft long, weighing in at over 25,000 lbs! For chambers one and four, 12 ft. diameter precast manhole risers were used to bring the chambers up to finished grade. The invert of existing sewer was over 30 ft. deep, making excavation and S.O.E. installation especially challenging. To make things a little easier, the VRH team decided to excavate the site down 10ft.

 

In order for chambers one and four to be constructed, C.A.C. had to set up one of the largest bypass pump system in NYC history. The existing 90’’ line runs completely full to the top of the pipe, so stopping flow was no easy task. With the help of En-Tech, we installed plugs or “balloons” inside the pipe and inflated them to 10 psi to create a stop in flow. These multi sized dome head plugs ranged from 54’’ to 96’’. Next, eight 20” bypass suction pumps were placed in behind the balloons and ran 24/7 while the chambers were being built. The pumps were 20’’ on the suction side and reduced to 18’’ on the discharge side. This gave the VRH team the ability to completely stop the flow, enabling them to build the tie in chambers totally dry. These pumps ejected approximately 60,000 gallons of sewer water per minute!

 

Once the chambers were constructed, the abandoned line was bulkheaded and filled with 748 yards of grout. On top of the bypass pumps, deep wells were drilled and 12 six-inch pumps were installed to keep the deep trench as dry as dry as possible. These pumps were put in at -62 ft. where they would pump 2.8 million gallons of water per day. Due to the high iron content in the ground, a sophisticated on-site filtration plant was set up to filter the water before it was discharged into the storm sewer. C.A.C. also had to install an additional well point system by Chamber 1 because the ground water at this particular location was worse than other areas of the site.

 

There were many challenges with this job, but like always the C.A.C. team prevailed and got the job done! Congratulations to the VRH team on completing this monumental project.