Serving Environmental needs for over 35 years

Hillsboro 4th Main Brownfield













The City of Hillsboro had purchased an underutilized corner lot in downtown Hillsboro in anticipation of redeveloping the property with a transit-oriented, compact, mixed-use project to fit into the City’s Downtown Plan.  When the City began to negotiate the sale of the property to a developer in 2011, HAI was retained to conduct a Phase I Environmental Site Assessment (ESA).  The Phase I ESA concluded that prior assessments may not have adequately investigated an historical fuel station and heating oil tanks at the property, and additional Phase II investigation was recommended.

Since the former fuel station footprint was covered by an existing vacant building (which was to remain as part of the proposed site re-development), the Phase II ESA included sub-slab soil gas sampling in the building to assess for Vapor Intrusion concerns, and groundwater sampling at inferred down-gradient locations to assess for significant releases at the fuel station, as well as soil testing at other locations.  The Phase II ESA determined that former fuel station operations did not adversely impact soil gas or groundwater, but did discover widespread petroleum contamination of soil from other sources, including shallow impacts from surface application of oils relating to historical livery and fuel station operations, and deeper impacts from three boiler fuel / heating oil underground storage tanks (USTs) at the property. 

HAI continued to characterize the magnitude, nature, and extent of contamination at the site, quantified volumes of contaminated soil, and collected adequate information to verify that risk-based closure was an option.  In addition, HAI prepared plans for the cleanup work and contaminated media management that were approved by DEQ.

HAI provided technical assistance to the City to facilitate a Prospective Purchaser Agreement (PPA) with the buyer of the property, as well as assistance to the City in obtaining a Brownfield loan and advice to all parties regarding cleanup approaches and timing.  The PPA, Brownfield loan, other lending, and sale of the property were all successfully completed on an expedited basis.

Site redevelopment began in August 2012.  HAI provided environmental oversight of remediation activities, which occurred during the excavation for a below-ground parking structure that was part of the planned four-story structure.  All told, over 5,300 tons of contaminated soil were segregated and removed from the property for appropriate disposal.  Three USTs were also removed during the work.  HAI oversaw the permitting and appropriate discharge for dewatered groundwater encountered during excavation activities.  The remedial work was documented in a Closure Report that was submitted to ODEQ to successfully complete this Brownfield cleanup project.  The new mixed-use 4th Main development opened for occupancy in 2014.


As a focused regional firm, we provide a personal approach, along with attention to detail, consistent high-quality work, and continuity of staff and services, including Phase I and II ESAs, Remedial Investigations, and Brownfield Redevelopment. The solutions we provide for our clients are formulated to promote responsible stewardship of the environment.