Dewatering and
Drainage Services:
Evaluation of soil and groundwater conditions
Analysis of aquifer and pump tests
Design of construction dewatering systems
Design of dewatering wells, vacuum well points and educator wells
Evaluation of flow rates, water quality and permitting needs
Construction observation of dewatering systems
Sound Transit has used Richard Martin on a couple projects to assist with very difficult groundwater / dewatering situations, each time achieving satisfactory results. The results of one particular dewatering program far exceeded our expectations; because of the method being used to construct large underground caverns in soft ground (the Sequential Excavation Mining method), we needed at least a 70% drawdown (35 feet) to perform the excavations safely, but Richard's dewatering system gave us a 100% (50 feet) drawdown, which allowed our Contractor to perform the excavation with no difficulties from groundwater. We look forward to working with Richard again in the future. - Richard A. Sage, PE CCM
Director of Construction Management, Sound Transit
Dewatering and Drainage Evaluation and Design
Challenging groundwater conditions required deep pumping wells, vacuum well points, and permanent drainage
One of the greatest sources of risk during subsurface excavations is uncontrolled groundwater inflow. In the absence of groundwater control measures, soils can run, causing excavation sidewalls to fail and excavation subgrade to become unstable and lose strength. If unidentified aquifers exist below the excavation, excessive hydrostatic pressure can cause uplift on the excavation base causing the subgrade to blow out. Proper design of dewatering and drainage systems can reduce these risks.
After system design, the most important part of a successful excavation below the water table is construction observation. Because of limited numbers of exploration locations and testing prior to design, variability in subsurface conditions is often encountered during construction. The ability to modify or change a system during construction results in fewer schedule delays and potential overall cost savings for the project.
West portal of Beacon Hill Tunnel beneath I-5
Richard has designed successful dewatering and drainage systems for a wide variety of projects from relatively simple sewer lines (City of Shelton, WA Infiltration and Inflow Reduction) and shallow excavations (333 Elliott Avenue, Seattle), to deep excavations with complex subsurface conditions (Beacon Hill Station, Seattle) and nearshore projects with challenging limitations and schedules (Naval Shipyard Drydock #6, Bremerton). His experience working with the owner's design team and on projects for the contractor’s team, as well as his construction management experience, provides his clients with a unique expertise that results in successful projects.
Richard has been an invited lecturer on "Contract Documents for Hydrogeologic Aspects of Projects" for the American Society of Civil Engineers Seattle Section Geotechnical Group Spring Seminar, April 20, 2013, and on "Computer Modeling and Contaminated Sites" for the American Society of Civil Engineers Dewatering Short Course, November 13-14, 2008.
Dewatering and Drainage Project Examples:
Construction Management for Sound Transit
University Link Light Rail, Seattle, WA
Northbound light rail tunnel opening from University Station
Richard is currently part of the Construction Management (CM) team evaluating soil and groundwater conditions for the Light Rail tunnel and cross passages between University Station and Pine Street, and Capitol Hill Station. He evaluated the contractor’s proposed dewatering design for Capitol Hill Station and provided recommendations for additional groundwater control measures and designed a temporary drainage system for use during buildout of the station.
For each of the cross passages, Richard reviewed soil and groundwater conditions and provided the CM team with recommendations for additional explorations. For Cross Passage 5, Richard performed and evaluated a pumping test and pilot-scale dewatering test, and designed an in-tunnel vacuum well point system to drain an aquifer overlying the crown of the cross passage. At Cross Passage 17 a previously unknown aquifer below the cross passage invert threatened to destabilize the cross passage excavation following a blowout during the contractor’s probing work. To reduce hydrostatic pressure beneath the partially excavated cross passage, he designed a combination passive gravity flow and vacuum well point system installed within the tunnel, and worked in collaboration with the contractor’s dewatering designer to design, install, test, and operate a dewatering well system installed at the surface.
Richard also provided recommendations for additional groundwater control measures, excavation sequencing, and a post-construction grouting program. The post-construction grouting program was designed to increase soil density around the cross passage, enhance the soil to structure connection, fill potential voids, and provide water-tight seals at the holes cored in the tunnel liner for the well points.
Sound Transit, Link Light Rail Beacon Hill Section, Seattle, WA
Beacon Hill shaft leading down to station excavation
Richard was Project Hydrogeologist for the Beacon Hill project segment, which consists of about 1 mile of twin 18.9 ft diameter transit tunnels, a deep underground binocular station with twin 550-ft long by 36-ft diameter platform tunnels, multiple shafts to the station, a west portal structure beneath Interstate 5 and opening towards the downtown and an east portal structure that provides access to Rainier Valley. Richard completed a redesign of the original dewatering system for the station and platform tunnels following the discovery of multiple water-bearing sand units near the crown of the structures and within the platform tunnel excavations. He reviewed groundwater elevation and dewatering system effectiveness on a regular basis and providing recommendations for operation and maintenance of the system. He also evaluated the effects of dewatering on groundwater conditions for the west portal structure crossing under Interstate 5 to determine impacts on column stability for the roadway.
City of Portland 3rd and Alder Diversion Structure and Outfall 28, East Side CSO, Portland, Oregon
Richard was Project Hydrogeologist for a sewer diversion structure and an outfall in Portland, Oregon. The diversion structure was located near 3rd and Alder near a settlement susceptible building and an area of known groundwater contamination. Richard constructed a groundwater model to perform parametric analyses of various dewatering scenarios. The modeling results indicated that a design consisting of multiple dewatering wells in different soil formations could effectively dewater the excavation while reducing the potential risk of adverse affects during construction.
For Outfall 28, adjacent to the Willamette River, Richard developed a groundwater model to evaluate the use of well points and deep dewatering wells to control groundwater during excavation. The model considered variable river stages. The final design consisted of multiple well points around the perimeter of the excavation and a deep dewatering well adjacent to the pipeline going into the river.
