HRSD 24″ Forcemain Abandonment
The Job
HRSD’s Virginia Beach Boulevard Forcemain Replacement project installed more than a mile of new pipe to replace an aging 24″ force main.
As part of decommissioning the original force main, it needed to be filled completely with grout.
The Challenge
Due to extensive widening of the roadway, the pipe was originally constructed alongside, extensive commercial and residential development, the number of access points needed to be as few as possible. This was driven by extensive structures over/adjacent to the old pipe, and a desire to reduce disruptions to adjacent stakeholders, and the risk of any utility strikes during access pit excavation.
The Solution
CJGeo grouted more than 7,000LF of the 24″ pipe over a period of four working days onsite. The pipe was completely filled, which was verified by uniform material venting from the far end of each run. Run lengths ranged from 450LF to more than 2000LF.
DeRuyter Reservoir Outfall Abandonment
The Job
The DeRuyter Reservoir, in DeRuyter, New York, is a 557 reservoir originally developed as part of the Erie Canal system.
As part of a dam upgrade project, the three parallel 22″ diameter, 300LF outfall pipes needed to be abandoned, along with a stone box culvert downstream of the valve chamber the pipes terminated into.
The Challenge
Each of the three pipes had been previously blindly flanged by divers. Therefore, the only access was from the downstream end within the valve chamber. In order to vent the air displaced by the abandonment grout, vent or placement points needed to be installed just behind the upstream blind flanges, which were approximately 40′ below the water surface.
The Solution
CJGeo worked with the general contractor to design an internal venting system utilizing sacrificial placement pipes installed from the valve chamber. After each of the sacrificial grout pipes was installed, the downstream terminations were bulkheaded, with vent stubs.
CJGeo mobilized a cellular grouting crew, who placed 30lb/cuft cellular concrete through each of the sacrificial grout pipes, until grout returned to the bulkhead vents, confirming fill. The work was completed over two days an onsite-the first day for the abandonment pipes and first lift in the box culvert, and the second day for a top-off pour on the box culvert.
8″ Toe Drain Abandonment
The Job
Lake Whetstone is an approximately 30-acre manmade impoundment located in Montgomery Village, Maryland. It is utilized for stormwater runoff control, and also recreation, with an approximately 1000LF earthen dam.
As part of a retrofit program of the embankment, two 8″, perforated CMP toe drain pipes need to be grouted for a minimum of 100LF, underactive flow.
The Challenge
Each of the two, 100′ long pipes needed to be grouted full, but could only be accessed from the downstream end of the pipes. One pipe had nominal flow, and the second pipe had approximately 10GPM and discharged through an end wall structure at the stilling basin.
The Solution
The project designer, Gannett Fleming, specified NSF Section 61 certified grout (potable water contact) for the abandonment grout. Due to the “one-shot” nature of the project, above-ground mockups, including sacrificial pipe installation, chemical grout cup testing, yield analysis, and visual inspection, were all required prior to the start of grouting.
CJGeo performed the onsite mockup testing and analysis, and then grouted the two pipes in place successfully over a period of two days onsite.
1 Mile 36″ Waterline Abandonment
THE JOB
CSX crews were surfacing the mainline track in Baltimore when the tamping equipment struck an object immediately below the ties. Investigation revealed that it was a manhole associated with nearly 6000LF of 36″ water main primarily running immediately below the tracks. The municipality relocated the waterline but was faced with the challenge of abandoning the pipe from just two intermediate points. There were three sections of pipe; 1200LF, 1600LF & 2900LF. Various solutions were floated, including threading sacrificial tubing and grouting on the way out, but none were economical or could guarantee a pipe abandonment below the railroad.
THE CHALLENGE
The project designer, OBG, identified cellular concrete as a potential solution to the problem and reached out to CJGeo to determine its feasibility. CJGeo confirmed the appropriateness of cellular concrete and set out to create a grouting plan. Coordination between the utility contractor and slurry provider (the site was too small to set up a batch plant) was crucial to ensure that the runs of pipe were all successfully filled in a single shot each. With train frequencies of 3-4 per hour, if the operation didn’t work and the pipes were only partially filled, there was no opportunity to create intermediate access points to finish grouting a section of pipe.
Based on the required bearing capacity and production requirements, CJGeo proposed 22lb/cuft cellular concrete for abandonment. With a 25psi break strength at 28 days, the mix provided the required strength, met the CSX utility occupancy standard for abandonment, and maximized expansion in order to ensure the longest run, which required nearly 1000CY of the finished product, could be grouting in a single shot.
THE SOLUTION
CJGeo mobilized a 150CY/hour cellular concrete crew to the site and performed the two shorter runs the first week. The project was broken into two different weeks due to the criticality of ensuring the longest run was filled completely without issue. The first two runs allowed CJGeo, the GC, railway flaggers, railway operations, and the slurry provider the opportunity to work out any kinks in operations during the lower risk placements.
The following Tuesday, starting at 0600, Chaney Enterprises delivered the first of 24 loads of slurry. Completeness of fill was confirmed by uniform cellular concrete venting out the far end of each placement. Overall, the work was completed in three days. CJGeo generated & pumped a total of 1710 cubic yards of cellular concrete to successfully complete the abandonment.
