Orchards & Pesticides: Solvable Problems

You’d be amazed just what percent of the Bay Area and greater Sacramento Area was formerly developed with orchards. What is particularly worrisome is that during this period of orchard development it was commonplace for farmers to utilize chlorinated pesticides for fruit protection. Not all sites are impaired, but it is important to know as much as you can about your site.

Although many of the compounds formerly used have since been banned, their residual concentrations still reside in the upper layers of the soil profile. And although it is true that these compounds are likely decreasing in concentration over time, due mostly to natural attenuation and chemical processes, it is also true that the concentrations that remain can be truly hazardous to current and future occupants. Though everyone has heard of DDT, there are also dieldrin, aldrin, and a whole host of more toxic compounds that have been used. You can't see this kind of contamination, only sampling of the soil can provide real world data for review.

If a site that was formerly orchards is being redeveloped for residential use, it is important to collect near surface soil samples to assess for the potential of residual pesticide contamination. We have found sites where –even though the site hasn’t been an orchard since the mid-1970s—the concentrations in the near surface soils exceed hazardous waste threshold criteria! The clean up of these compounds, which are primarily chlorinated pesticides, PCBs, arsenic, lead, and mercury, is usually off-hauling of contaminated materials and backfilling with imported soils. This is an easy and effective method of ensuring that future occupants are protected from historic uses. Most of these compounds affect children disproportionately more than their adult counterparts.

Not every site requires remediation, but knowing what is present either prior to purchase of the site, prior to redevelopment of the site, or prior to re-use of the site, is critical. Only on-site sampling and a trained consultant can guide what should be done. In most instances site conditions are OK, and even in these cases the results of sampling bring peace of mind.

Everyone involved in a transaction involving historic orchards has a stake in ensuring that future use of the site occurs alongside a responsibility to protect those future occupants.