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 needed to be grouted for a minimum of 100LF, under active flow.
The Challenge
Each of the two, 100′ long pipes needed to be grouted full, but could only be access 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 “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.
Bulkhead Sinkhole Grouting
The Job
With an annual throughput capacity of 48 million tons, Norfolk Southern’s Pier 6 at Lamberts Point in Norfolk, Virginia is one of the largest coal transloading facilities in the world. As a round-the-clock facility built around precision logistics, there’s little tolerance for disruption or downtime.
The Challenge
When two sinkholes opened up at the end of Pier 6 adjacent to the bulkhead, railroad personnel reached out to an onsite maintenance contractor. Steel plates were installed to provide temporary protection while a long term solution could be implemented.
The Solution
CJGeo performed DCP testing at the site in order to quantify the depth of voids below the pavement adjacent to the sinkholes. The DCP testing showed that in addition to large voids visible from the sinkholes immediately below the pavement, there were large pockets of voids down to 15’ below the surface.
CJGeo crews then used CJGrout 35NHV61, a hydroinsensitive, NSF-certified geotechnical polyurethane to fill all voids and restore stability to the area. The grouting work took five hours onsite to install 3400 pounds of material, with zero disruption to operations.
Chemical Underpinning
The Job:
Water began to seep through the floor of the shop, break room and bathrooms inside a manufacturing facility. Investigation determined that a water line had broken, and weekend soils below the floor, causing the settlement. Voids were also present.
The Challenge:
The client’s primary concern was addressing the stability of the area without affecting normal usage.
CJGeo’s Solution:
CJGeo proposed chemical grouting to stabilize the weakened soils, along with polyurethane grouting to fill voids. Previous repairs to address floor settlement had been completed, so a hydroinsensitive undersealing polyurethane grout was used to ensure stability without lifting the slab.
Sand Filter Joint Sealing
The Job:
Two underground stormwater sand filters at an apartment community wouldn’t hold water. The structures, which were assembled from 10′ diameter metal pipes needed to pass a water loss test before the property could come off bond. Previous repairs attempted included 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 were bedded in washed #57 stone, and were connected to the stormwater drainage system, so subject to live flow.
CJGeo’s Solution:
Sprayed high density polyurethane/polyurea hybrid to seal the joints internally. In addition, chemical grouting for joints which had been repaired previously using internal bands and polyethylene seals. The chemical grouting repair was designed to minimize loss of chemical grout into the surrounding stone beds. The previously-installed internal seals and bands were left in place and encapsulated in the joint sealant.
CJGeo large diameter pipe repair crew installed chemical grout to seal the leaking joints. Immediately after the sealing was performed, the structures were tested by the municipality. Neither structure leaked any water after CJGeo sealed the joints.
Warehouse Floor Water Intrusion Repair
The Job:
An area of floor inside of a produce processing facility experienced water intrusion through joints in the floor. Considerable amounts of process water were dumped on the floor each day, and unsealed joints in the floor allowed water to collect under the floor slab. With dynamic loading from material handling equipment, water was displaced through the joint onto the floor. The facility’s health & safety staff was concerned that the water could introduce contaminants to the food processing area.
The Challenge:
The proposed repair had to perform well in saturated conditions, allow for near immediate resumption of material handler equipment, and ensure a longterm fix. Since no settlement had occurred, the grout material had to be able to seal the very small voids, displace water, and not exert any lifting forces on the floor.
The material & process also had to be performed at cold temperatures–the facility is maintained at 34 degrees year-round.
CJGeo’s Solution:
CJGeo proposed chemical grouting using a hydrophilic prepolymer grout. Chemical grouting is ideal for saturated environments and helps to ensure complete stabilization and sealing of floors.
A single CJGeo chemical grouting crew mobilized to the site and performed the work in a few hours. The work started after second shift, and was completed in time for the grout to set and tolerate material handling equipment at the start of first shift.
The following day, the facility reported no water extrusion under material handler traffic.
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 had to be done without disrupting traffic in the parking lot. 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 structure walls.
CJGeo’s Solution:
Chemical grouting using both prepolymerchemical groutingand 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.
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. A low exotherm structural foam was chosen due to the very large size of the void. Structural foams are important in situations where there are very large voids in areas subject to traffic loading.
Dam Outfall Pipe Seep Grouting
Dam outfall pipe seep grouting, Fairfax, Virginia
Problem:
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.
Constraints:
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 vehicle down a steep slope.
While unknown during the planning of the chemical grouting repair, what was thought to be 36″ RCP was actually larger diameter RCP that had been lined with steel casing pipe. An interior poured-in-place concrete liner had been installed afterwards.
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. and 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 of the leak.
Result:
The initial grouting plan was to install the chemical grout through the pipe wall starting beyond the first joint in. 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.
