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LOCATION:  Baltimore, Maryland

PROBLEM:  Erosion of Subsoils Below Concrete Roadbed,  Track Movement

DATE OF PROJECT:  December 2011 – March 2012


URETEK ICR – Northern US was asked to review a project involving track ballast stabilization in Baltimore, MD.  It had been determined through surface observations that voids were present below a 32 in thick concrete railway substructure due to erosion by a constant flow of drainage water collecting beneath the ballast sub-structure.

Track Ballast Info

Track ballast forms the trackbed upon which railway sleepers are laid. It is packed between, below, and around the ties. It is used to facilitate drainage of water, to the load from the railroad ties, and also to keep down vegetation that might interfere with the track structure. This also serves to hold the track in place as the trains roll by. It is typically made of crushed stone, although ballast has sometimes consisted of other, less suitable materials.

Observations of the track included a differential in elevation and displacement of large quantities of water during track occupancy by passing trains. Voids below the roadbed were initially estimated by the customer to be as deep as 12 inches and encompassed several hundred feet of track.

Issues with accessibility, track geometry, the presence of high volumes of water and time constraints were all major concerns of the client. URETEK ICR – Northern US was able to address every client concern and meet their very specific needs.

In December of 2011 the pilot project was scheduled and completed. Based upon the success of the pilot project, URETEK ICR – Northern US was given the ‘green light’ to proceed and finish up the two subsequent phases of the three-phase project.


URETEK ICR – Northern US proposed four options which included on and off track application as well as two different options for drill patterns. The proposed solutions offered the client flexibility in controlling cost and scheduling. Taking into consideration the characteristics of the material selected for the project, equipment capabilities and flexibility in scheduling, an option was selected which allowed for off track application of the area during scheduled outages coordinated with the client’s Maintenance of Way Department .

The customer then initiated a pilot project consisting of a section of concrete roadbed measuring 100 feet by 12.5 feet. The pilot project was to test out and prove the effectiveness of the patented URETEK processes and materials in the filling of subsurface voids, elimination of further destabilization due to water infiltration, and the stabilization of the railroad roadbed.

URETEK ICR – Northern US technicians drilled through the roadbed utilizing a predetermined grid pattern and set up laser monitoring equipment to detect vertical movement. Injections were made directly through the roadbed until lift of <1mm was detected.  The URETEK ICR – Northern US crew was able complete work on the 100 ft. section of track in less than 18 hours including set up, tear down and patching of injection points over the course of two days.

The pilot project proved that the URETEK ICR – Northern US solution was able to meet the railroad’s specification for void fill, water elimination, and roadbed stabilization.


During the first phase of application, it was found that voids were less extensive than originally projected. Less than 30% of the material requested for this project was consumed during the pilot phase.

Subsequently, the customer requested that additional track in the immediate vicinity of the pilot project, with the same erosion problem, be repaired in the same manner. Change orders were granted to include an additional 300 ft. of track being stabilized during two scheduled outages in January and March of 2012.


 Each Phase:  Day One –

The URETEK ICR – Northern US crew staged for application and monitoring/measurement and began drilling the injection grid pattern for the application of our patented structural geo-polymer material.  Additionally, probes were inserted at multiple locations to determine roadbed thickness and the extent of existing voids, which were fully documented. The presence of water was found and verified at each probe location. Laser level monitoring equipment was placed in order to ensure track geometry was not compromised during application.

Once several sets of holes were pre-drilled, the crew commenced with geo-polymer injection while additional injection points were drilled out.  Geo-polymer was injected at two adjacent locations simultaneously until slight movement was detected. The crew then moved to the next set of injection points and repeated the procedure until all injection points were shot. Project time on-site for Day One was eight hours.

Each Phase:  Day Two –

The URETEK ICR – Northern US crew staged for Day Two in the same fashion as Day One. The injection process was done in a precise manner and pattern so as to ‘redirect’ subsurface water around the road bed and towards an existing sump pump. Upon completion of stabilization work on Day Two, all drill out points were patched and site cleanup was performed, followed by a site inspection. Project time, on site Day Two – ten hours.

Cumulative project time, per phase, for each 100-150 linear feet of roadbed was between 18-20 hours.

Project Modification: URETEK ICR – Northern US altered the application process to drill injection points and probe simultaneously with material injection. This increased productivity to 75 linear feet per day (150 linear feet per outage), a productivity increase of approximately 50% per outage. This afforded the customer control over their track outage periods through coordination of track stabilization work in conjunction with other scheduled track projects..

During each of the track outages, URETEK ICR – Northern US crews were able to fill voids, eliminate water infiltration, restore proper water flow, and stabilize the roadbed for between 100 and 150 linear feet of track in under 20 hours including set up, breakdown, clean up and final inspection by the customer.


URETEK ICR – Northern US counts this as a successful project because our customer deems this a successful project.  Both agree that these factors contribute to the success of the project:

  • The project was completed within the tight track outage timelines established by the customer.
  • The speed and efficiency of the URETEK ICR – Northern US crew and the unique, proprietary material characteristics allowed the customer to repair four times the track length originally specified, within the same budgeted cost.
  • Co-scheduling with other customer-related projects allowed for project completion without the need for additional track outage scheduling.
  • Subsurface water was redirected and the roadbed stabilized.
  • The customer is already exploring how to engage URETEK ICR – Northern US to stabilize more roadbed within this next fiscal/budget year.


The URETEK ICR – Northern US processes, products, experience, and crew skill allowed the customer to exceed their original repair specification without disrupting rail operations. The customer was able to get 4X the track length repaired within the same budget.

The customer remarked that he was very, very pleased with the effectiveness of the process and products, that the URETEK ICR – Northern US crew set a new ‘high water mark’ in professionalism and effectiveness during the project phases, and that URETEK ICR – Northern US is a top choice for further mitigation of ballast fouling, railway track substructure stabilization, and general fouling maintenance requiring specific time table for completion in the future.