Current through Register Vol. XLI, No. 50, December 13, 2024
Section 61-22-8 - Basis for Assessment and Planning8.1. Vulnerability Assessment 8.1.a. The assessment of the vulnerability of groundwaters to agricultural and non-agricultural point and nonpoint source contamination will require the cooperation of state agencies. Information concerning soil properties, hydrogeology, aquifer properties, usage of pesticides and fertilizers and known contamination will be used to identify areas sensitive to point and nonpoint source pollution. These areas will be targeted for closer examination by the Department of Agriculture or other appropriate agencies.8.1.b. Data required include: Soil properties: physical, chemical and/or biological properties; unsaturated zone organic carbon and clay content; and rates of water travel through the unsaturated zone. Aquifer properties: depth to groundwater; recharge areas; discharge areas; rates of travel in the saturated zone; and wellhead protection areas. Irrigation and rainfall data. Pesticide and fertilizer usage and leaching data.8.1.c. Evaluation of the relationships between the above factors will be conducted by all participating agencies using general integrative techniques such as modeling, DRASTIC, and GIS systems to identify areas in the state that appear or are most likely to be vulnerable to contamination. However, more weight will be given to actual data than predictions due to modeling, as modeling is not a definitive predictor of water movement, but the technique is valuable as a reference point.8.2. Pesticide and Fertilizer Assessment8.2.a. State management plans will be developed for specific pesticides and fertilizers when either predictive models which indicate likelihood of leaching in vulnerable areas or monitoring data demonstrates an existing or potential problem.8.2.b. Chemicals of concern will be identified by considering physicochemical properties including: water solubility, soil adsorption, soil degradation, hydrolysis and rate, timing or method or application. Predictive models such as GLEAMS, CREAMS, PRZM and the Environmental Resource Conservation Service pesticide-soil matrix will be utilized. Predicted ground-water concentrations will be compared to health-based water standards to determine chemicals which are predicted to exceed standards under certain conditions or are shown to have an increasing concentration in the groundwater.8.2.c. Use patterns of identified chemicals of concern will be examined along with existing monitoring data. If the chemical has been used extensively in vulnerable areas and monitoring data fails to demonstrate detections exceeding standards or trends which threaten to exceed standards in the future, a management plan is not required. However, if sufficient monitoring data is unavailable or if the chemical in question does not have a history of use in the area and could be used in the future, a management plan could be initiated.