Over the last several years, the EPA and other organizations have taken a very aggressive stance when it comes to sanitary sewer overflows (SSOs) and correcting the problems of inflow and infiltration (I & I). The EPA has issued several high profile administrative orders regarding these problems. Recently, the city of West Palm Beach, Fla. faced an administrative order regarding discharge from its sanitary sewer mains.
As a solution to the problem, the city turned to NUCA contractor Arrow Directional Boring, Coral Springs, Fla. for the installation of a sanitary sewer force main. The multi-faceted contractor specializes in trenchless technology including pipe ramming, pipe bursting, horizontal boring and directional drilling. For the project in West Palm Beach, the contractor combined pipe ramming with directional drilling to overcome tough working conditions.
Arrow Directional Boring Vice President Jeff Blake said, “The city was experiencing problems with I & I in its sanitary sewer system. During periods of heavy rain, the sanitary system would back-up into the gravity system and top the manholes. This was especially troubling because sewage would eventually find its way into the inter-coastal waterway. The force main system is designed to eliminate this problem by increasing the system’s capacity.”
The project called for the installation of 11,000 feet of 12- and 18-inch HDPE force main through directional drilling. The Arrow crew divided the runs into 1,000-foot segments. When tough soil conditions and extreme depth halted one pullback 100 feet short of completion, Blake opted to assist the pullback with the percussive power of a Grundoram pipe rammer from Associate NUCA member TT Technologies, Aurora, Ill, in hopes of successfully completing the bore.
Several pipe ramming techniques have been developed over the last few years to assist directional drill rigs in difficult situations. The techniques have been used to successfully remove stuck drill stems, assist directional drill rigs during difficult pullbacks, free immobilized product pipes and even salvage failed bores by removing stuck pipe from the ground.
TT Technologies product specialist Frank Fresneda said, “By utilizing the percussive action of the Grundoram pipe rammer we can really help drilling operations. These techniques can help avert costly situations where product pipes or drill stems get stuck. We’re actually seeing drilling contractors bring pneumatic pipe rammers to job sites as a kind of insurance policy. It’s been very positive for the industry and worked well in West Palm Beach.”
One of the most difficult drilling segments of the project took place under the northbound lane of a highly traveled roadway, at a depth of 15 feet. The fine sand conditions compounded the problem, making it difficult to maintain a bore-hole.
According to Blake the crew anticipated problems for that particular installation of 18-inch HDPE. He said, “During back-reaming we kept running into an area that was giving us a hard time, right around the 900-foot mark. We couldn’t find anything specific however. On our first back-ream, which was 18 inches, we got hung up. We were going to use a 32-inch back-reamer, but at that point decided to use a more aggressive 27-inch reamer; and we were able to get through the tough section. Then we decided to pull the pipe in with the 32-inch reamer, but were stopped about 100 feet short of completion.”
Blake had actually utilized the pullback assist technique on previous projects. After calling Fresneda and explaining the situation, an18-inch diameter Grundoram Goliath pneumatic pipe rammer arrived on site the next day. The Arrow crew attached the pipe rammer to the end of the HDPE product pipe and began ramming. After an hour, the percussive action of the pipe rammer began to free the HDPE. The Arrow crew was then able to pull the pipe into place with the drill rig, without further problems.
Blake said, “The hammer worked extremely well for the directional assist. Everyone involved with the project was really pleased with the results.”
Fresneda said, “Jeff [Blake] and the entire Arrow crew are top-notch contractors. They’ve been in difficult situations before, but they have a tremendous amount of experience and are able to find the right solutions to get through the tough projects.”
NUCA, July 2002