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Dewey-Humboldt Soils Investigation




Contaminants of Concern (COCs): 

Possible lead in soil at concentrations over the background level.

Discovery Date: 

December 2019

Affected Media:


Site Summary:

Two soil samples were collected on a parcel of land owned by Chevron USA and located northwest of the Humboldt Elementary School. The soil samples were analyzed using a portable, handheld X-ray Fluorescence (XRF) Analyzer. One of the samples had an XRF reading of 1,384 parts per million (ppm) of lead.

ADEQ was notified of this lead concentration and its proximity to the Humboldt Elementary School, and is initiating an investigation. Since these parcels are privately owned, the process included contacting Chevron USA, the owner of the land where the lead concentration was detected, and the Town of Dewey-Humboldt, the owner of two adjacent parcels. ADEQ then worked with the owners to acquire access agreements in order to conduct soil sampling to evaluate metals concentrations in soils. In addition,  ADEQ hired a contractor to prepare a work plan, to conduct the soil sampling event, and to prepare a report to summarize and present the results of the investigation.

Note: This soils investigation is not affiliated with the Iron King Mine-Humboldt Smelter EPA Superfund site in Dewey-Humboldt. For more information related to EPA's Superfund Site,  visit the EPA website | Visit Iron King Mine-Humboldt Smelter EPA Superfund Page >

Status Update

The Final Soil Investigation Report was released in February 2021. ADEQ provided the final report to the current property owners and has been in communications with the current owner for addressing any further concerns.


Soil Sampling Report | View/Download >

December 2020 Community Update | View/Download >

February 2021 Community Update | View/Download >

Work Plan | View/Download >

Demolition and Soil Remediation Report (November 2021) | View/Download >

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