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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Facing a similar challenge to this toe drain abandonment project? Give us a shout or shoot us a text. Click the state marker for the location of your project for contact info for the appropriate rep.
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.
Speak With An Expert
Facing a similar challenge to this dam outfall pipe seep grouting project? Give us a shout or shoot us a text. Click the state marker for the location of the project for contact info for the appropriate rep.
