Acid Drainage Grouting
The Job
This acid drainage grouting project is located in West Virginia. A 72″ CMP stream diversion pipe under a coal stockpile at a coal mine in West Virginia was experiencing acidic water infiltration. This was causing bypassed stream water to become acidic, so regulators required all of the stream flow to be pumped to treatment ponds and treated. This was expensive, and the flow volume was greater than the design capacity of the treatment system.
The Challenge
Access was quite challenging. The pipe was either 700LF or 1300LF from the nearest access points to the farthest grouting location. Additionally, the infiltrating water was pH 2.
Due to location, all personnel had to be MSHA 40 hour trained, and the company registered as a mine contractor with the state.
The Solution
CJGeo recommended a hydrophobic prepolymer chemical grout with an extensive performance history in high acidity environments. CJGeo crews sealed a combination of 20 joint leaks and point infiltration sources using the prepolymer chemical grout.
To address acidic water migrating through the stone dust backfill outside of the pipe, CJGeo crews then grouted an in-situ cutoff wall in the trench just downstream of the lowest leak using permeation grouting. Permeation grouting is optimal for creating small footprint cutoff walls because it typically doesn’t require large equipment. The mine operator installed two dewatering wells immediately upstream of the cutoff wall to intercept and pump out the acidic drainage, to keep it isolated from the stream water.
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RCP Pipe Sealing
THE JOB
This RCP pipe sealing project is located in Wake Forest, North Carolina. The asphalt parking lot over a 300′ run of 54″ RCP culvert kept collapsing. The locality’s public works department determined that the installation crew had not properly gasketed or seated the joints between the 4′ sticks of pipe. The pipe saw the continuous flow of a small stream. Flow enters at an end wall and discharges into a box culvert that crosses a public street. The drop inlet at the downstream junction between the RCP culvert and box culvert also had a failed 18″ RCP culvert feeding it. This had been repaired multiple times using open trench excavation.
THE CHALLENGE
The municipality was looking for an affordable, proven, and non-disruptive solution. Replacement would have required removal of a structure, and prevented adjacent businesses from using their parking lot during the work. Relining was not practical due to multiple sewers and water utility lines crossing through the pipe. Significant joint offsets would have also made lining difficult.
Extensive voids were identified around the pipe through an inspection. Much of the water flow from the stream was passing under/outside of the pipe, causing the erosion and collapse of the overhead parking lot, and the floor of a storage building built over the pipe. Previous attempts at sealing the joints and filling voids around the pipe with concrete had failed.
THE SOLUTION
Polyurethane grouting fill voids around the pipe and seal the joints between the individual pieces of pipe, end wall and drop inlet. And, chemical grouting to treat a curtain at the upstream end to reduce subsurface flow, and at the downhill end to stabilize a joint in the failed small diameter RCP culvert entering the drop inlet.
CJGeo polyurethane grouting crews placed 50 cubic yards of CJGrout 35NHV61, hydro insensitive polyurethane and 45 gallons of polyurethane resin chemical grout for an upstream grout curtain over a period of three days to complete the repair. The repairs were all completed without disruption to the adjacent businesses or streets.
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15 inch RCP point repair
The Job
This 15 inch RCP point repair project is located near Richmond, Virginia. A 6′ deep sinkhole opened up adjacent to a stormwater manhole structure. The manhole was in an easement between two single-family homes and maintained by a municipality. Two misaligned joints were visible from the manhole and were the cause of the sinkhole.
The Challenge
The two misaligned joints were under up to 8′ of cover. The repair had to seal the two misaligned joints and fill the extensive voids around the pipe that resulted from years of erosion.
Due to extensive utilities in the area, and difficult access, the owner did not want to perform an open cut repair. While the misalignment was significant, the reduced flow from the misalignment was less problematic than an open cut repair.
The pipe is located approximately 150 feet from the nearest roadway, on a steep slope towards a resource protection area. All of these factors significantly increased the costs & disruption of an open cut repair.
The Solution
CJGeo proposed grouting via driven tubing to seal the joints in the pipe. An internal form was used to minimize the entry of chemical grout into the pipe.
CJGeo’s large diameter pipe repair crew installed CJGrout 35NHV geotechnical polyurethane to seal the two misaligned joints and fill voids. The repair took less than two hours, with no service disruptions. CJGrout 35NHV excels at repairing failed RCP joints because its reaction profile is designed for void filling, and it’s unaffected by water. The homeowners and owner were happy that the repair only took foot traffic and a lightweight 2″ hose bundle.
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Sand Filter Joint Sealing
The Job
This sand filter joint sealing project is located in Richmond, Virginia. Two underground stormwater sand filters at an apartment community wouldn’t hold water. The structure is four, twenty foot sticks of ten foot diameter CMP. It had to hold water before the property could come off the bond. Previous repairs attempted included the installation of internal joint rings and seals, which did not stop enough flow to pass the water loss tests.
The Challenge
The proposed repair had to accommodate multiple layers of previous repairs. The joints included four different materials–aluminized metal, galvanized metal, neoprene, and polyethylene. The structures are in a bed of washed #57 stone, and subject to live flow.
The Solution
Sprayed high-density polyurethane/polyurea hybrid to seal the joints internally. In addition, chemical grouting for joints with internal bands and polyethylene seals. A fast set reaction kept the chemical from migrating into and fouling the stone bed. The spay application and encapsulates the original repair’s joint seals.
CJGeo’s large diameter pipe repair crew installed chemical grout to seal the leaking joints. Then, each joint was sprayed with a hybrid polyurea-polyurethane internal seal. Immediately after the sealing was performed, the structure held water and passed the water loss test. Neither structure leaked any water after CJGeo sealed the joints.
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HDPE Joint Repair
The Job
This HDPE joint repair project is located in Virginia. A sinkhole opened up in a drainage easement maintained by an HOA. The cause of the sinkhole was an improperly-seated joint between two 24″ HDPE stormwater pipes. The sinkhole was large enough that a few minutes of digging with a shovel exposed the entire joint.
The Challenge
The pipe was too small to enter to perform a repair. The joint was also out of spec for a reliable test & seal grouting application.
The Solution
CJGeo recommended chemical grout injection into the joint from the outside of the pipe to grout the annulus between the ID of the female and OD of the male end of the joint.
CJGeo performed this HDPE joint repair in less than two hours onsite. Single component chemical grout injection successfully sealed the entire circumference of the joint. Visual inspection via injection holes was used to confirm the complete travel of chemical grout around the entire area of the joint.
Because the pipe was so accessible, it was very easy to drill into the annulus from the sinkhole and grout the joint externally. This avoided having to perform a traditional trenchless repair process like cured in place pipe lining.
After getting visual confirmation of the entire bell & spigot joint being full of grout, CJGeo backfilled the hole.
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Sinkhole Repair
The Job
A sinkhole opened up in a drainage easement maintained by an HOA. The cause of the sinkhole was identified as an improperly-seated gasketed joint between two 36″ HDPE stormwater pipes. The pipes were approximately 5 feet below the surface, where there was a 3′ diameter sinkhole.
The Challenge
The pipe had been poorly installed, so it suffered extensive ovaling due to compression of the top during compaction without lateral support.
The Solution
Chemical grout injection into the sinkhole from the surface to fill the sinkhole and seal the pipe joint.
Stormwater Pond Outlet Structure Grouting
THE JOB
This stormwater pond outlet structure grouting project is located in Washington Township, New Jersey. The stormwater pond in a neighborhood was not holding water. Geotechnical investigations of the lining material showed that it was adequate. The developer determined that outlet structure grouting may be required to address water loss around the buried structures.
Due to a very tight site, the pond design releases water through two structures feeding manifolds. The pond has a well and pump to make up for water loss. However, the pond would still not stay at the level. The inlet and two outlet structures were identified as potential flow paths for water exiting the pond, causing the level to drop.
The township engineer told the developer that if they could not get the pond to hold water, they were going to have to install a liner system, which was very expensive.
THE CHALLENGE
Any repair could not impact:
- water quality,
- well operations, or
- the residents.
The repair had to address water flows through various seepage paths around the structures. Due to the open graded stone pipe bedding for the manifold outlet system, there were countless potential flowpaths.
THE SOLUTION
CJGeo successfully performed chemical grouting for the outlet structure grouting. This stopped water migration through the stone beds on two outlet structures and an inlet structure. During the grouting work, significant amounts of grout came into the manifold distribution boxes. This indicated that they were not watertight, and allowing water to seep into them at lower elevation than their design inlet elevations. The work took one day to make the structures watertight.
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HDPE Pipe Joint Sealing
THE JOB
A large sinkhole opened up in the parking lot of a manufacturing facility. The sinkhole was adjacent to a cast-in-place stormwater drop inlet structure. The structure was 14VF deep and was fed and discharged by 54″ HDPE pipes, requiring HDPE pipe joint sealing.
Facility maintenance personnel had been monitoring the sinkhole and noted that it was growing rapidly. Inspection of the pipe revealed that there were joint failures at the first joint out from the manhole and deterioration of the parging. The parging between the HDPE and concrete pipe had failed to the point of significant amounts of soil washing out during rain events.
THE CHALLENGE
The repair could not disrupt traffic in the parking lot or other facility operations. It also had to provide a long-term solution to the failed pipe joints.
Along with gently filling the voids around the HDPE pipe without deflecting or damaging it, the repair material had to have enough expansive force to thoroughly seal the small cracks and leaks in the parging between the HDPE pipe and concrete structural walls.
THE SOLUTION
Chemical grouting using both prepolymer chemical grouting and plural component polyurethane grouting.
Chemical grouting was chosen for injection through the joints of the HDPE pipe. Prepolymer chemical grouting uses single component polyurethane grouts with exceptionally long gel times. This virtually eliminates localized expansive pressure, which could further damage the HDPE pipe, which was already out of round.
The plural component structural foam was used for void filling the large sinkhole that extended from the bottom of the structure to the surface.
Prepolymer chemical grout was injected through the joints in the HDPE pipe. This successfully sealed the bell and spigot joints without causing further deflection of the pipes.
The large sinkhole void was grouting using plural component polyurethane grouting. Due to void size, CJGrout 20SDB is the best material due to its low exotherm. Structural foams are important in situations where there are very large voids in areas subject to traffic loading.
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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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Stormwater Pipe Repair
The Job
This stormwater pipe repair project is located at a chemical manufacturing plant in Petersburg, Virginia. The facility manager discovered a large sinkhole adjacent to a secondary containment structure holding a 10,000 gallon tank. The sinkhole appeared to extend far under the footprint of the containment structure. The structure is approximately 20 feet by 40 feet.
The Challenge
The containment structure, which was cast-in-place concrete, was coated with a coating designed specifically for the chemical makeup of the tank’s contents. Therefore, drilling holes through the floor of the structure to fill voids below it wasn’t possible.
The Solution
CJGeo proposed polyurethane grouting to seal joints. A CJGeo crew spent one day onsite installing CJGrout 35NHV61 to seal the joints and fill the sinkholes. The grouting process reestablished uniform support to the structure.
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