| Low Risk | Low - Moderate Risk | Moderate - High Risk | High - Risk | |
| Location (all tanks) | ||||
| Position of tank in relation to drinking water well. | Tank downslope more than 100 feet from well in medium - or fine textured soils (silt loam, loam, clay loams, silty clay) with low per - meability. | Tank at grade or upslope more than 100 feet from well in medium or fine textured soils (silt loam, loam, clay loams, silty clay) with low per - meability *. | Tank downslope more than 100 feet from well in coarse textured soil (sands, sandy loam,) with high per - meability. | Tank at grade or upslope less than 100 feet from well in coarse textured soil (sand, sandy loams) with high per - meability. |
| Tank Location and local land use (leakage potential). | Well drained soils. Water table always beneath tank. Above ground tank more than 50 feet from buildings. | Moderately well drained soils. Only occasionally high water table. | Located more than 50 feet from buildings. Medium or fine textured soils (silt loams, loam, clay loams, silty clay) saturated seasonally. | Located less than 50 feet from buildings and in areas with fine textured soils (clay loams, silty clay, clay) often saturated. |
| Design and Installation Table. (all tanks). | ||||
| Type and age of tank corrosion protection. | Synthetic tank or tank with cathodic corrosion protection.. | steel tank less than 15 years old, coated with paint or asphalt. | Coated steel tank 15 or more years old. Bare steel tank less than 15 years old. | Bare steel tank 15 or more years old. |
| Spill and tank overfill protection. | Impermeable catch basin plus automatic shutoff. | Impermeable catch basin plus overfill alarm. | Impermeable catch basin or concrete catch pad. | No protection. |
| Piping. | Piping protected from rust and corrosion by cathodic protection. Piping isolated from tank and sloped back to tank. Check valve at pump (not at tank). | Piping galvanized but not isolated from tank. Pipe drains back to tank. Check valve at pump. | Piping galvanized, not isolated or bare. Piping sloped back to tank, but check valve is located at tank (foot valve). | Piping and tank isolated and of dissimilar materials. Uninsulated pipe bare, cannot drain freely to the tank. All pressure pipe systems |
| tank installation. | Installed by state certified installer. | Installed according to recommenda - tions provided with new tank by seller. | No information installation. | Installed without backfill, setback, secondary contain - ment, anchors and other protection, or by untrained individual. |
| Design and Installation (above ground tanks only). | ||||
| Tank enclosure. | Tank surrounded by 6 foot tall non combustible building or fence with lock. Building well ventilated. Firewall in place if setbacks do not conform to code. | Tank surrounded by low fence with lock. Firewall in place if setbacks do not conform to code. | Tank surrounded by los fence. No lock. No firewall. | No enclosure. |
| Secondary contain - ment. | Tank placed within concrete of synthetic dike with pad able to hold 125% of tank capacity. | Tank placed within dike and pad made of low per - meability soils*, able to hold 125% of tank capacity. | Tank placed on pad. | No secondary contain - ment. |
| Monitoring (all tanks). | ||||
| Tank integrity testing and leak detection monitoring. | Regular (monthly) leak monitoring. | Daily inventory control and annual tank tightness testing. | Occasional inventory control and annual tank tightness testing. | No inventory control, testing or monitoring. |
| Tank closure (under - ground tanks). | ||||
| Unused tank. | Tank removed from ground. Excavation checked for evidence of contamin - ation. | Tank filled with inert material and excavation checked for evidence of leaking. | Tank removed or filled with inert material. Excavation not checked for contamin - ation. | Tank left in ground (illegal after 12 months). |
| * See glossary. |
|
TEX*A*Syst is a series of publications to help rural residents assess the risk of ground water pollution, and to describe Best Management Practices (BMPs) that can help protect ground water. The TEX*A*Syst documents were developed from the national Farm*A*Syst ground water protection program. The TEX*A*Syst system is designed to help the user learn more about the environment, existing environmental policies and regulations, and recommended management practices. Thus, the user can voluntarily reduce the pollution risks associated with water wells.
TEX*A*Syst materials were edited by Anna Schuster Kantor, and reviewed by M.C. Dozier and the personnel of the USDA-Natural Resources Conservation Service, U.S. Environmental Protection Agency, Texas Department of Agriculture, Texas Natural Resource Conservation Commission, Texas Water Development Board, Texas State Soil and Water Conservation Board, Texas Water Resources Institute, and Texas Farm Bureau. Editorial and formatting assistance were provided by the Department of Agriculture, The Texas A&M University System. |
September 20, 1998
Dennis Hoffman, Project Leader
Steve Dagitz, Webmaster