Drastic maps are composites made up of eight individually mapped hydrogeological parameters. Seven of these parameters (depth to water - Dw, net recharge - Nr, aquifer media - Am, soil media - Sm, topography - T, impact of the vadose zone - Iv and hydraulic conductivity - Hc) are used to derive the DRASTIC summary index score. The eighth, hydrogeologic setting, is useful for general map interpretation but, it is not included in the summary index.
Pesticide DRASTIC is designed to be used where the activity of concern is the application of pesticides to an area. It represents a special case of the DRASTIC Index. The only way in which Pesticide DRASTIC differs from DRASTIC is in the assignment of relative weights for the seven DRASTIC factors. All other parts of the two indexes are identical; the ranges, ratings and instructions for use are the same. If the user is concerned with the ground water pollution potential of an area by pesticides, then the weights for Pesticide DRASTIC should be used.
Scale is an important factor in data usage. Certain scale data sets are not suitable for some projects, analysis, or modeling purposes. Please be sure you are using the best available data.
1:24000 scale data sets are recommended for projects that are at the county level. 1:24000 data should NOT be used for high accuracy base mapping such as property parcel boundaries.
1:100000 scale data sets are recommended for projects that are at the multi-county or regional level. 1:250000 scale data sets are recommended for projects that are at the regional or state level or larger.
Vector datasets with no defined scale or accuracy should be considered suspect. Make sure you are familiar with your data before using it for projects or analyses. Every effort has been made to supply the user with data documentation. For additional information, see the References section and the Data Source Contact section of this documentation. For more information regarding scale and accuracy, see our web pages at: