Murphy Pipeline Contractors of Jacksonville, Florida, USA was recently employed by two municipal authorities in Florida, USA for the replacement of two corrugated (CMP) storm sewer pipelines using the pipe bursting technique. The two projects were undertaken for the City of DeLand and Hillsborough County.
However, whilst many trenchless lining/rehabilitation methods exist that could be used to renew or renovate a CMP storm sewer, these options generally will not work when the original pipe has a partial or full collapse.
In the City of DeLand, Florida, after recently rehabilitating all of the storm drains in a neighbourhood, there was still one pipe that could not be cleaned properly or fully inspected due to a partial collapse. The 18 in (450 mm) diameter CMP storm drain ran from a retention overflow structure and between two houses to a lake. The location of the pipe meant that an open cut operation was simply not an option. Ground conditions across the site comprised wet sandy soils. On this project the launch pit for the pipe bursting system was located next to the lake.
In Hillsborough County, Florida, after a partial collapse of an 18 in (450 mm) diameter CMP storm sewer, a homeowner’s back yard started to flood. The local utility first sliplined the main with a new 8 in (200 mm) diameter) HDPE pipe, which was the largest size of new pipe that could be installed through the collapsed section. However due to flow requirements during wet weather events, the utility needed
to replace the storm sewer with a new 18 in (450 mm) diameter pipeline. For this operation the pipe bursting system was located in a start pit next to the nearby storm retention pond with the sandy soil ground conditions again being wet.
Murphy Pipeline Contractors was able to offer both clients a trenchless option for replacement of both of the CMP pipes using the Static pipe bursting technique. This option allowed the collapsed CMP pipes to be replaced size-for-size with new HDPE pipe, with the pipe bursting operation being to operate through the partial collapses. In the case of the Hillsborough County operation, the recently slip lined HDPE pipe was split and expanded out simultaneous with replacing the CMP pipe.
To complete both installations Murphy Pipeline Contractors utilised a TT Technologies Grundoburst 2500G with a specifically designed cutting tool and expander head. Each project replaced around 200 ft (61 m) of CMP pipe with the new HDPE DR 11 pipe.
According to Murphy Pipeline Contractors, GIS maps were used for the design with minimal route design being required as the static pipe bursting technique follows existing utility path.
For both installations the new 18 in (450 mm) diameter HDPE DR 11 pipe was butt fused to the required length using McElory fusion equipment.
On the Deland project just 4 days were required from the start of works to completion. Similarly, the Hillsborough County project was also completed in just 4 days.
According to Todd Grafenauer, of Murphy Pipeline Contractors: “No problems were encountered during either of the static pipe bursting operations. This was most likely due to the custom tooling and expander design ed for and utilised on the projects.”
Todd continued: “Both projects required floating of the fused HDPE pipe used for the replacement installations. On the DeLand project the pipe was floated in the lake and for the Hillsborough County site it was floated in the nearby storm retention pond. This enabled the launch pit located next to the water to be used as the insertion pit. In Hillsborough there was some concern on the part of the home owner when moving the HDPE pipe that it would not disturb the property’s mature landscaping and earth works, so the contractor utilised a hand cart to move HDPE pipe, eliminating any potential disturbance to the landscaping.”
One of the client organisations commented that: “Static pipe bursting was the only solution to address problem. Lining methods were ruled out due to the partial collapse and open cut options were ruled out due to proximity to homes. The only other option was installing a lift station and re-routing the main to an area more that was more accessible, however this option was extremely costly.”
For Murphy Pipeline Contractors, Todd closed by saying: “CMP replacement with static pipe bursting is no longer prohibitive due to the advancements in the available burster and expander tooling.”