Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Incident reports can play an important role in evaluating the effects of pesticides by supplementing
quantitative risk assessments. All incident reports for pesticide(s) with the active ingredient and
associated information would be recorded.
Environmental Fate
Water Solubility: Service personnel would record values for water solubility (Sw), which describes
the amount of pesticide that dissolves in a known quantity of water. Sw is expressed as mg/L (ppm).
Pesticide Sw values would be categorized as one of the following: insoluble 10,000 ppm (US Geological Survey 2000). As pesticide
Sw increases, there would be greater potential to degrade water quality through run-off and leaching.
Sw would be used to evaluate potential for bioaccumulation in aquatic species [see Octanol-Water
Partition Coefficient (Kow) below].
Soil Mobility: Service personnel would record available values for soil adsorption coefficient (Koc
[μg/g]). It provides a measure of a chemical's mobility and leaching potential in soil. Koc values are
directly proportional to organic content, clay content, and surface area of the soil. Koc data for a
pesticide may be available for a variety of soil types (e.g., clay, loam, sand).
Koc values would be used in evaluating the potential to degrade groundwater by leaching (see
Potential to Move to Groundwater below).
Soil Persistence: Service personnel would record values for soil half-life (t½), which represents the
length of time (days) required for 50% of the deposited pesticide to degrade (completely or partially)
in the soil. Based upon the t½ value, soil persistence would be categorized as one of the following:
non-persistent 100 days (Kerle et.
al. 1996).
Threshold for Approving PUPs:
If soil t½ ≤100 days, then a PUP would be approved without additional BMPs to protect water
quality.
If soil t½ >100 days, then a PUP would only be approved with additional BMPs specifically to
protect water quality. One or more BMPs such as the following would be included in the Specific
Best Management Practices (BMPs) section to minimize potential surface run-off and leaching
that can degrade water quality:
• Do not exceed one application per site per year.
• Do not use on coarse-textured soils where the ground water table is 12 inches.
• Do not use on steep slopes if substantial rainfall is expected within 24 hours or ground is
saturated.
Along with Koc, soil t½ values would be used in evaluating the potential to degrade groundwater by
leaching (see Potential to Move to Groundwater below).
Soil Dissipation: Dissipation time (DT50) represents the time required for 50% of the deposited
pesticide to degrade and move from a treated site; whereas, soil t½ describes the rate for degradation
G-38 Appendix G. Integrated Pest Management