Recently Anderson Environmental Inc received a request to determine the risk for soil use for vegetable production for soil which was contained in large garden beds made of treated lumber. Lumber retaining walls in the garden beds were suspected to have been Chromated Copper Arsenate (CAA) treated and/or to have been painted with Creosote. Leachate from these timbers has the potential to contaminate the soils within the beds. Application of the Alberta Tier 1 Soil Remediation Guidelines resulted in of a total of 10 samples being collected from the soils of the garden beds near to the wooden retaining walls. Samples were distributed throughout the beds generally within 30cm of the treated lumber. These samples were collected at a depth of 5-15cm. Samples were analysed for Arsenic (As) (five samples) as well as a total of 23 Creosote-associated Polycyclic Aromatic Hydrocarbons (PAHs) (all samples). The results were assessed against the values of the Alberta Tier 1 Soil and Groundwater Remediation Guidelines for fine soils intended for agricultural land uses. Of the samples submitted for analysis, all contained Creosote-related PAH concentrations in excess of the Alberta Tier 1 Soil Remediation Guideline levels. Arsenic concentrations were found to be below guideline levels.
With migration above guideline levels at 30cm from the treated lumber it was recommended that the soil not be used for the intended purpose. The migration of chemically treated timber has also been found to leach initially to nearby wetland environments in research undertaken by the US Forest Service. As such when you are considering vegetable production please consider the potential risks involved with treated products.
As Environmental Consultants in Calgary and Edmonton we occasionally get unusual requests beyond our normal range of assessments which provides for interesting work. We undertake a range of assessments including: Phase 1 ESA and Phase 2 ESA, Biological Assessments, Wetland Assessments and Soils Assessments and Water Quality Testing however occasionally we receive interesting requests which are quite specific. Why not give us a call for any assessments you require.
Resources:
https://open.alberta.ca/dataset/842becf6-dc0c-4cc7-8b29-e3f383133ddc/resource/a5cd84a6-5675-4e5b-94b8-0a36887c588b/download/albertatier1guidelines-jan10-2019.pdf
http://www.calgary.ca/UEP/WRS/Pages/What-goes-where/Wood-Creosote-treated.aspx
https://nationalpost.com/pmn/news-pmn/canada-news-pmn/alberta-worried-about-creosote-site-chemicals-near-edmonton-residential-area
https://www.cbc.ca/news/canada/edmonton/pretty-nasty-chemicals-alberta-orders-cleanup-at-former-creosote-treatment-plant-in-edmonton-1.3912726
