Phase I Environmental Site Assessment (ESA)

Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), a property owner may be held accountable for cleanup expenses associated with environmental contamination, even if it originated prior to his/her ownership.

Potential buyers, as wells as lending or refinancing institutions, often request a Phase I ESA prior to property transactions. This Due Diligence process identifies the potential for the presence of environmental conditions solely through the research of databases, historical imagery, and site-reconnaissance. No invasive methods are conducted during the data collection process of this assessment. Phase I ESA’s are conducted and presented in accordance with current ASTM standards.

Phase II ESA

If recognized environmental conditions are identified during the Phase I ESA, a subsurface investigation will likely be required. This investigation, known as a Phase II ESA, focuses on evaluating the site’s subsurface conditions to confirm or rule out the presence of environmental contamination. This process includes the collection and analysis of soil and groundwater samples, via test bores, groundwater monitoring wells, or minor excavations. Phase II ESA’s are conducted and presented in accordance with ASTM standards and Colorado Division of Oil and Public Safety (OPS) guidelines.

Corrective Action Plan (CAP) Design & Implementation

In the event that contamination is confirmed, a CAP must be designed and implemented to mitigate environmental impacts. Our goal is to provide sensible solutions. We always consider the financial needs of our clients without compromising the quality of our remediation techniques.

GSC has certified environmental consultants that can design, install, and maintain a varity of remediation systems.

Petroleum Storage Tank Consulting

When Aboveground Storage Tanks (AST’s) and/or Underground Storage Tanks (UST’s) have lost their physical integrity, they may need to be removed to prevent contamination. Tanks may also be removed if they are not being used or if a company seeks to upgrade their fuel system.

GSC has qualified personnel and the necessary equipment to conduct the following activities associated with UST/AST removal:

  • Waste characterization of tank contents
  • Removal and disposal of tank contents
  • Excavation and removal of tank(s)
  • Tank decommissioning, cleaning, and disposal
  • Site restoration, including backfilling and grading
  • Sampling of soil and groundwater
  • Preparation and submittal of closure report

Tank removal is not always practical. If the tank is in good condition and there is no contamination associated with it, the tank may be temporarily or permanently closed in place.

Regulatory Compliance

Inspection testing must be performed on regulated petroleum storage tanks on monthly and annual bases.
GSC has qualified personnel to audit properties for compliance with local, state, and federal regulations. GSC has permitted A/B Operators that may perform monthly and annual inspections to UST systems. Additionally, GSC provides assistance with preparing annual compliance reporting required by the Environmental Protection Agency (EPA) and Colorado’s Division of Oil and Public Safety (OPS).

Spill Prevention, Control, & Countermeasure (SPCC) Plan

Facilities that have an aggregate aboveground storage capacity greater than 1,320 gallons, or a completely buried storage capacity greater than 42,000 gallons need a SPCC plan. If the facility is a farm with more than 10,000 gallons of aboveground storage capacity, a retail fuel station, or a bulk plant, the SPCC must be certified by a licensed Professional Engineer (PE). GSC works with licensed Professional Engineers and has qualified staff that prepares SPCC plans.

State Funding and Reimbursement

GSC personnel works closely with OPS to minimize the financial impact of environmental cleanup. We have experience completing Reimbursement Applications (RAP’s) to allow our clients access to state remediation funds.

Specific Services Provided

Vacuum Truck Services

GSC owns and operates a vacuum truck that is utilized for the following applications.

  • Removing contaminated groundwater and soil vapor via Enhanced Fluid Recovery (EFR)
  • Removing free phase product during emergency response
  • Excavation dewatering
  • Secondary containment cleanup
  • Tank contents removal
  • Hydro Excavating/Potholing

In-Situ Chemical Injections

This is an environmental remediation technique, used to degrade contaminants in soil and groundwater, through the injection of specific chemicals at targeted intervals. GSC is equipped to inject in-situ treatment chemicals in a wide variety of subsurface conditions.

Soil Boring and Monitoring Well Installations

GSC owns and operates a drill rig with direct-push and auger drilling capabilities. Our drilling team has vast experience collecting soil samples from various terrains in accordance with ASTM standards. We also use our drill rig for installing the following:

  • Recovery wells
  • Soil vapor monitoring wells
  • Groundwater monitoring wells
  • Air sparge wells
  • Soil vapor extraction wells
  • Temporary groundwater monitoring wells

Sampling & Field Screening Services

GSC has the necessary equipment to collect and screen groundwater, surface water, soil vapor, ambient air, and soil samples in accordance with ASTM standards.


Performing an excavation is often the most timely and cost-effective method to mitigate an environmental condition. Furthermore, in the event of a minor spill, a quick response and removal of surficial soil will likely prevent additional cleanup costs. GSC personnel have vast experience coordinating and performing large and small scale excavations.