Pennsylvania Pipe Abandonment
The Job
This Pennsylvania pipe abandonment project is located at a drinking water reservoir near York, Pennsylvania. As part of a dam reconstruction, the existing outfall pipe was specified for grouted abandonment.
The Challenge
The existing outfall pipe is 48″ cast iron pipe, and approximately 200 feet long. The pipe passes approximately 45 feet below the crest of the earthen embankment, concrete core dam structure. To ensure that the pipe would not serve as a conduit for water after abandonment, the specification calls for cellular grout with a maximum permeability of 1×10-6 centimeters per second.
During design, there were concerns about leaks in the pipe draining out some of the cellular concrete after placement stopped, but before it reached initial set. To address this, a secondary grouting program using chemical grout was designed to top off any void volume in the outfall pipe after the cellular grout set.
The Solution
CJGeo proposed using 60lb/cuft CJFill-Standard cellular grout for the abandonment. 60lb/cuft CJFill-ST exceeds the minimum compressive strength requirement, and has less than 1×10-6 cm/sec permeability.
CJGeo mobilized a dry batch cellular grout plant to the site to complete this Pennsylvania pipe abandonment project. The crew performed the grouting in fewer than two hours. The dry batch plant generates the 60lb/cuft cellular grout onsite directly from bulk cement powder.
Placement was through sacrificial grout pipes installed by the general contractor. The GC also constructed masonry bulkheads on both ends of the structure.
Exploratory holes drilled in the bulkheads the following day confirmed uniform fill, and no need for the secondary grouting work.
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Microtunnel Contact Grouting
The Job
This microtunnel contact grouting project is located in Clarksville, Tennessee. It is part of a new water intake structure along the Cumberland River to improve the reliability of the city’s municipal water source.
The Challenge
Based on the overcut of about an inch, and length of the 450 foot long tunnel, the contact grouting volume was approximately 50CY. In order to efficiently place the grout against the roughly 40′ of head from the river that that the tunnel terminates in, high volume, high quality mixing was required.
The tunneling contractor reached out to CJGeo to use onsite colloidal batching to generate grout quickly, safely, and without the risks of using ready mix.
The Solution
CJGeo proposed using a 0.55 water : cement ratio slurry generated onsite with colloidal mixing for the contact grout. While there were nearby ready mix plants that could have supplied the job, mixing neat grouts in transit mixer trucks typically does not uniformly wet out the cement. This can make it very difficult to pump, and typically results in highly variable mixes. Because the grout is the same as the cement slurry used for making CJFill cellular concrete, CJGeo used a cellular concrete batch plant with the foam generator turned off.
CJGeo batched and placed 50CY of slurry over about 2.5 hours to complete the microtunnel contact grouting. Placement of the grout was through 2″ ports, and the grout displaced both the lubricating bentonite slurry, and significant amounts of water. Due to the exceptionally high mobility of colloidally mixed neat cement grout, CJGeo’s crew was able to grout the entire length of the tunnel from two ports located just in from the launch shaft.
Grout communication was confirmed through lubricating ports, visual confirmation from the casing pipe drying due to heat of hydration, and divers in the river witnessing grout at the tremied bulkhead.
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Illinois Spillway Grouting
The Job
A spillway serving as a dam for a lake owned & maintained by a property owner association outside of Carbondale, Illinois stopped having water flowing over the spillway, requiring spillway grouting. The property owners determined that the lake was draining through voids under the spillway slab. This made them concerned about destabilization of the spillway, which was the sole access for six homes.
The Challenge
The flow velocity was rather high, and immediately on the other side of the spillway was a 30′ cliff. The water was designed to spill over as a waterfall. Given the extraordinary difficulty of retrieving any material washed over the waterfall, the grout had to have an exceptionally fast set. It also needed to provide adequate bearing capacity for the roadway slabs.
The Solution
CJGeo proposed grouting below the spillway with CJGrout 40NHL. CJGrout 40NHL is usually used for differential settlement correction. CJGrout 40NHL performs well for differential settlement correction because it reacts very quickly. It’s used for medium duty lifting, such as highway pavement, so it would provide more than enough bearing capacity.
The owners were very excited that it would be significantly less expensive to grout the existing spillway than to have someone local install a portadam and replace the entire structure. CJGeo mobilized a single polyurethane grouting crew to the site. They stopped the leaks and kicked all the water flow over the spillway in a single day.
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Spillway Bridge Grouting
The Job
This spillway bridge grouting project is located in Toano, Virginia. Toano is between Williamsburg and Richmond. Two DOT-maintained bridges crossing two privately owned dam spillways had to be closed because of extensive undermining of the spillways.
The undermining was allowing nearly all of the flow to happen below the spillway slabs. This caused large sinkholes to form adjacent to and under the roadway pavement. It also led to some settlement of the spillway slabs.
The Challenge
There was very little room to work–just under 4′ of clearance below the bridge beams. Also, the velocity of the water through the voids below the structure was quite high.
The Solution
CJGeo proposed a combination of plural component polyurethane grouting to address the water flows and voids, and hydrophobic chemical grout placed directly into cracks. A single CJGeo grouting crew was able to complete the repairs in a day (roughly 2500sqft of work, and approximately 4500lbs of CJGrout 35NHV61 polyurethane, plus 30 gallons of hydrophobic chemical grout). Dye testing during and after the grouting work confirmed that no more leaks were present under or around the spillway structures.
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Low Level Outfall Abandonment
The Job
This low level outfall abandonment grouting project is located in New Jersey. The Round Valley Reservoir, in Clinton Township, New Jersey is a 2300 acre man-made drinking water reservoir. It serves extensive portions of New Jersey. It was constructed by damming up two openings in a naturally-curved mountain.
As part of a dam upgrade project, a 1400LF, 36″ inner diameter LLO pipe needed to be grouted to place it out of service.
The Challenge
The pipe had been previously blind flanged, 180′ below the lake surface. There was a single, 12″ riser pedestal. There were numerous significant challenges to face, including:
- 2GPM residual leak from the blind flange buried in 15′ of lake floor debris
- inability to push sacrificial pipes more than 500′ up the pipe
- remote site with limited ready mix service
The Solution
CJGeo worked with the general contractor, diving subcontractor, sacrificial grout pipe installation subcontractor, geotechnical and civil EORs, and the owner, to develop a single stage grouting plan to place approximately 350CY of 68lb/cuft CJFill-Under Water cellular grout from the downstream end.
Venting was achieved by installing a 4″ removable vent pipe from the pedestal riser. The vent pipe ran 180VF to the lake surface, terminating on a barge. There was only one opportunity to do the job correctly. Therefore, CJGeo had two fully staffed grout plants onsite, and had all cement and mix water staged in onsite storage. This was all prior to the start of grouting to avoid any material logistics disruptions affecting the work.
CJGeo placed the 68lb/cuft grout over a period of a few hours, leaving an intentional air pocket at the high end to capture infiltrating lake water long enough for the grout to set prior to seeing lake head.
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DeRuyter Reservoir Outfall Abandonment
The Job
This outfall abandonment project is located in Upstate New York. The DeRuyter Reservoir, in DeRuyter, New York, is a 557 reservoir that’s originally part of the Erie Canal system.
As part of a dam upgrade project, the three parallel 22″ diameter, 300LF outfall pipes were 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. The blind flanges are 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 CJFill-Ultra Lightweight cellular concrete through each of the sacrificial grout pipes, until grout returned to the bulkhead vents, confirming fill. The work took two days. 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.
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Toe Drain Abandonment
The Job
This toe drain abandonment project is located outside of Washington, DC. Lake Whetstone is an approximately 30-acre manmade impoundment located in Montgomery County, Maryland. The approximately 1000LF earthen dam provides stormwater runoff control and recreation.
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, under active flow.
The Challenge
Each of the two, 100′ long pipes needed to be grout filled. The pipes are only could only be accessable from the downstream end of the pipes. One pipe had nominal flow, and the second pipe had approximately 10GPM of flow. Each discharges 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.
While most abandonment grouting uses high mobility cement grout, like CJFill-Ultra Lightweight, chemical grout was the best option for this abandonment. Chemical grout’s reaction speed (and therefore mobility) is controllable onsite by variable catalyst dosing. This helps ensure minimizing any migration of grout into adjacent structures or waterways.
CJGeo performed the onsite mockup testing and analysis, and then grouted the two pipes in place successfully over a period of two days onsite.
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Dam Outfall Pipe Seep Grouting
THE JOB
This dam outfall pipe seep grouting is located in Fairfax, Virginia at Northern Virginia Community College. A 36″ RCP outfall pipe for a dam terminated at an end wall. As part of a dam rehabilitation, small seeping leaks at the end wall/pipe joint needed to be stopped. The leaks had to be stopped so the wall could be resurfaced.
The engineer specified chemical grouting.
THE CHALLENGE
Access to the area was quite difficult. It was more than 150 feet from the closest vehicle access, which was only accessible by 4×4 vehicles down a steep slope.
While unknown during the planning of the chemical grouting repair, what was thought to be 36″ RCP was actually a larger diameter RCP that had been lined with steel casing pipe. An interior poured-in-place concrete liner had been installed afterward.
THE SOLUTION
Super low viscosity prepolymer chemical grout was selected. This was for two reasons: 1) the ability to easily pump more than 150LF from the lay-down area. 2) the ability to seek out and stop leaks through very tight cracks in the structures.
Prepolymer chemical grouts are water-reactive, so can be injected into active water flows. The grout expands when it comes into contact with the water, which seals the leak.
The initial grouting plan was to install the chemical grout through the pipe wall starting beyond the first joint. However, because the pipe had been cased, placement had to be done through the end-wall structure only. Multiple injection holes were drilled through the end wall structure, and the chemical grout was pumped through the end-wall structure.
Extensive catalyzation was used to first seal the leaks at the end wall and then chase the water flow pathways up along the outside of the pipe. The job was messy due to the forced proximity of the injection points and the leaks. But all the leaks were successfully stopped.
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