Deep Vertical Aquifer Profile (VAP) Investigation

Project Overview:

A leading global engineering firm engaged Summit to perform a deep vertical aquifer profile (VAP) investigation at a complex site in South Carolina. The objective of the program was to generate high-resolution vertical profiles of volatile organic compounds (VOCs) in groundwater to better understand contaminant distribution within deep saprolite, fractured bedrock, and potential preferential water-bearing zones. The work involved advancing multiple deep borings using roto-sonic drilling and collecting discrete soil and groundwater samples at targeted depth intervals.

Challenge/Conditions:

The project required drilling to depths of up to 200 feet below ground surface, but site conditions ultimately required advancement to nearly 300 feet at certain locations. Tight silts and variable subsurface conditions caused multiple instances of tooling becoming locked in the borehole at depths exceeding 200 feet. These conditions posed significant operational risks, including the potential loss of large-diameter sonic tooling, while still requiring completion of precise sampling objectives.

Services Provided:

• Roto-sonic drilling at six VAP locations
• Advancement of borings to competent bedrock or maximum depths (up to 300 ft bgs)
• Detailed soil classification based on color, lithology, grain size, texture, and moisture
• Soil screening above the water table using photoionization detector (PID) for VOCs
• Collection of up to five discrete groundwater samples per location using temporary well screen, packer assembly, and submersible pump
• Targeted sampling at just below the water table, presumed preferential water-bearing (PWR) zones, and top of competent bedrock or terminal depth
• Measurement and documentation of field parameters (pH, DO, ORP, conductivity)
• Sample handling, preservation, and chain-of-custody shipment to laboratories
• Boring abandonment using neat cement grout in accordance with SCDES requirements

Solutions/Approach:

Summit deployed an experienced sonic drilling crew led by a driller highly specialized in VAP sampling and deep drilling applications. When tooling became locked within tight silt zones at extreme depths, the team applied controlled recovery techniques to safely retrieve both 6-inch and 8-inch tooling without compromising borehole integrity or losing equipment. Field personnel worked closely with the customer's geologist to dynamically select additional sampling intervals based on observed lithology and permeability, biasing data collection toward the most effective transport zones. This collaborative, adaptive approach ensured the project remained technically sound despite subsurface challenges.

Outcome/Results:

Summit successfully completed all VAP borings and sampling activities, recovering all tooling and delivering the depth-specific soil and groundwater data required by the customer. Despite drilling significantly deeper than originally anticipated, the project remained productive and met the client's investigative objectives. The successful execution reinforced Summit's capability to perform high-risk, deep sonic drilling and VAP investigations under demanding subsurface conditions.