Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Remediation® Conference

Tuesday, November 4, 2008 : 11:10 a.m.

Evaluation of Continuous Trenching Method for Construction of Vertical Barrier Walls

Stephen C. Lindsay, EIT1, Darren S. Quillen, P.E.1 and William R. Morse2, (1)Environmental Resources Management Inc., (2)Sunoco Inc.

Vertical barrier walls (VBWs) are often used as the primary component of a remedial technology designed to contain, collect, and/or treat petroleum-contaminated, or otherwise impacted, groundwater.  Depending on the remedial objective, a VBW may be constructed of a low or high permeability material.  There are various materials and methods used for construction of a low permeability wall (LPW).  These alternatives include slurry walls, shallow soil mixing (SSM), jet grouting, sheet pile, clay barriers, and geosynthetic walls.  Additional options are available for permeable walls including sand or gravel collection trenches and reactive walls.  Numerous factors affect the installation and performance of these walls, such as geology, depth of wall, groundwater characteristics, access, and wall geometry.  Each technology has corresponding advantages and disadvantages relative to these factors.  Nonetheless, whether using traditional excavation equipment to construct a slurry wall or specialized equipment to install a geosynthetic wall, VBW construction is a rigorous task that typically requires significant time and expense.

In recent years, a continuous trenching technique was modified for the construction of VBWs and has been successfully applied to environmental remediation projects.  The technology utilizes a unique excavation and backfilling process that is performed in a single “pass” by the equipment.  LPWs are constructed using a vertical cutting bar that continuously mixes the reagent(s) in-situ, thereby, reducing material handling and construction schedule.  Permeable walls are excavated by the cutting bar and simultaneously backfilled, eliminating open trenches and stability issues.  Where applicable, this technique has significantly reduced installation costs and schedule.  Case histories involving the use of the single-pass installation technique will be presented to demonstrate the advantages and disadvantages associated with this method.  The case histories will focus on the applicability, limitations, cost, and schedule from project experience to better identify the appropriate application and situation for this alternative.

Stephen C. Lindsay, EIT, Environmental Resources Management Inc. Mr. Lindsay is a civil engineer with over four years of experience in investigation, design, permitting, and construction of soil, sediment, surface water, and groundwater remediation projects, design and permitting of solid waste management facilities, geoenvironmental analysis and design, demolition and dismantlement, soil erosion and sediment control, stormwater management, land development, and compliance permitting. Site remediation experience primarily includes addressing impacts from hydrocarbons and metals. Mr. Lindsay also has experience providing construction management and oversight services on remediation projects.

Darren S. Quillen, P.E., Environmental Resources Management Inc. As a professional engineer with 15 years of experience in the civil and geoenvironmental field, Mr. Quillen has served as project manager, engineer, and construction manager on numerous disposal, remediation, and civil engineering projects throughout the country. Responsibilities have ranged across the spectrum of project types and sizes including investigation, design, permitting, construction, and certification. Project work has primarily included waste disposal, remediation, land development and brownfields projects, and construction management. Through various Superfund, RCRA, and state regulated projects, Mr. Quillen has applied numerous innovative remedial designs including in-situ stabilization, vertical walls, geosynthetics, caps and liners, phytoremediation, and integrated re-use.

William R. Morse, Sunoco Inc. Mr. Morse has more than 20 years of professional experience in environmental programs, regulatory strategy and site remediation. He is responsible for managing projects wherein he is accountable for scope and budget, resource allocation and risk management for several refineries and CERCLA sites. His background includes the assessment and treatment of soil and groundwater in connection with site remediation and the regulatory approvals required for each.


Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Remediation® Conference