Environmental Project

Soil and Stream Remedial Investigation and HHRA at Former Sugar Mill

Confidential Developer Aiea, Oahu, HI

Solution Overview


Confidential developer

Business Challenge:

  • Assessment and remediation of a site with challenging physical characteristics


  • Targeted approach to identify areas of concern and rule out exposure pathways in unlikely areas


  • A cost-effective approach that saved the client time and significant remedial effort, resulting in major cost savings


Based on the site’s historical use as a sugar mill, to comply with current regulatory requirements, the site required a remedial investigation, a human health risk assessment (HHRA), and a remedial alternatives analysis. The site’s physical components also presented a challenge for both assessment and remediation activities.


Our risk assessment included a remedial investigation of the property to be acquired and delineation of constituents of concern (pesticides, herbicides, arsenic, and lead). Impacted soil was found along the stream banks and streambed.

Using the data collected during the remedial investigation, a HHRA was prepared for current and potential future exposure scenarios. Because the site was impacted with lead, blood lead modeling was performed using the US Environmental Protections Agency (EPA) Integrated Exposure Uptake Biokinetic (IEUBK) Model for lead in children and the Adult Lead Methodology (ALM).

Complex health risks and remedial issues were encountered at this site for several reasons:

  • An ephemeral stream transected the site
  • The stream bank slopes were very steep
  • Access to the site was physically limited


Apex Companies developed select remedial actions for the site that provide for reliable, cost-effective, and long-term solutions. By integrating the findings of the human health risk assessment, a remedial approach was selected that met acceptable risk levels and minimized the volume of soil requiring removal/treatment.

The site, essentially a streambed gulch, was highly unlikely to be developed in the future because of the severe stream bank slopes, presence of an ephemeral stream, and limited site access. However, lead concentrations exceeded residential and commercial action levels.

Our team was able to demonstrate through the preparation of a HHRA that lead concentrations on the vast majority of the site were health protective. Because of the unlikelihood that the site would be developed, potential exposures would be to the most probable receptors, in this case child trespassers. As a result, remedial alternatives could be developed for a much smaller area of the site while meeting health protection goals.

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