SOURCE WATER DELINEATION AND ASSESSMENT REPORT Rosebud School District #12 Public Water System PWSID MT0001656 Date of Report: April 11, 2006 Mort Barrus, Certified Operator 1 Main St Rosebud, MT 59347 phone: 406 347 5353 Prepared By Karen LaClair and Steve Custer Montana State University Bozeman, MT 59717-3480 PH: 406 994 6906 EXECUTIVE SUMMARY ..................................................................................................... 3 INTRODUCTION ................................................................................................................... 5 CHAPTER 1 - BACKGROUND ............................................................................................ 6 The Community ............................................................................................................................................ 6 Geographic Setting ...................................................................................................................................................... 6 General Source Water Description ............................................................................................................... 7 The Public Water Supply .............................................................................................................................. 7 Water Quality ................................................................................................................................................ 8 CHAPTER 2 - DELINEATION ............................................................................................ 10 Hydrogeologic Conditions .......................................................................................................................... 10 Conceptual Model and Assumptions .......................................................................................................... 12 Well Information ......................................................................................................................................... 13 Limiting Factors .......................................................................................................................................... 13 CHAPTER 3 - INVENTORY ................................................................................................ 14 Inventory Method........................................................................................................................................ 14 Inventory Results/Control Zone .................................................................................................................. 15 Inventory Results/Inventory Region ........................................................................................................... 16 CHAPTER 4 - SUSCEPTIBILITY ASSESSMENT .............................................................. 20 Susceptibility Analysis Results ..................................................................................................................... 9 REFERENCES CITED .......................................................................................................... 9 GLOSSARY .............................................................. ERROR! BOOKMARK NOT DEFINED. APPENDICES ..................................................................................................................... 11 APPENDIX A - FIGURES ................................................................................................... 12 Figure 1. Rosebud vicinity map ............................................................................................................ 13 Figure 2. Private and public water supply wells in the Rosebud vicinity .................................................. 15 Figure 3. Rosebud school well inventory vicinity. .................................................................................... 16 Figure 4. Rosebud school pws recharge region. Arrows approximate recharge flow direction ............... 17 Figure 5a. General Rosebud area geology (Ross and others, 1955) .......................................................... 18 Figure 5b. Detailed Rosebud area geology (Stoner and Lewis, 1980). Arrows approximate flow direction. Each square is six miles across. ................................................................................................. 18 Figure 5c. Map key for detailed geologic map. ......................................................................................... 19 Figure 5d. Lithologic descriptions for detailed geologic map. ................................................................. 19 Figure 6. Land cover of Rosebud school pws inventory and control zones............................................... 22 Figure 7. Land cover of Rosebud school pws recharge region .................................................................. 23 Figure 8. Land cover by percent for the Rosebud school PWS inventory zone ........................................ 24 Figure 9. Land cover by percent of the Rosebud school PWS recharge region ......................................... 25 APPENDIX B - SITE PLAN ................................................................................................ 26 APPENDIX C - WELL LOG(S) ........................................................................................... 28 APPENDIX D - SANITARY SURVEY ................................................................................. 32 APPENDIX E – DEQ WATER QUALITY REPORT ............................................................ 33 2 EXECUTIVE SUMMARY This Source Water Delineation and Assessment Report (SWDAR) was prepared as required by the Federal Safe Drinking Water Act and in accordance with Montana’s Source Water Assessment Plan. The Department of Environmental Quality (DEQ) is completing assessment and delineation reports for all public water systems in Montana. Source water assessment is the first step towards source water protection. These reports are intended to provide information and help public water system staff/operator, consumers, and community citizens develop strategies to protect drinking water sources. The information provided includes the delineation of the area most critical to maintaining safe drinking water (the inventory region), an inventory of significant potential sources of contamination within this area, and an assessment of the relative threat that these sources pose to the water system. This PWS’s uses ground water as its source of drinking water and uses one well to provide the water. The well is located to the rear of the school building. The well is reported to be completed in early 1989 to a depth of 240 feet. However, there is no driller’s log available listing construction, lithology, or aquifer information for the well. As a consequence, the source aquifer for the Rosebud School well is unknown. A majority of wells in the vicinity of the school’s wells appear to be completed in the shallow alluvial aquifer and range in depths from 23 to 162 feet. Wells completed in the deeper aquifer range in depths from 318 to 402 feet (GWIC). The sanitary survey reports that the Rosebud School well is flowing under artesian pressure. This lends evidence to the well being completed in the deeper, confined Hell Creek Formation. A complete copy of the sanitary survey is in Appendix D. As part of this assessment, four types of source water protection areas are mapped or delineated. They are: the control zone, the inventory region, the recharge region, and a surface water buffer. The control zone (sometimes called the exclusion zone) is a 100-foot radius circle around the wellhead. The goal of management in the control zone is to avoid introducing contaminants directly into the well or immediate surrounding areas. The inventory region is delineated as 1,000 foot fixed radius circle that is used when an aquifer is interpreted to be confined (DEQ, 1999). The recharge region represents the area that is expected to contribute water to the well over long periods of time. A surface water buffer region is used when a stream flows on top of the aquifer used by a public water supply. Potential sources of pathogens and nitrate are inventoried for the surface water buffer and recharge regions. Potential sources of contamination inventoried within the source water protection regions are as follows: Potential sources of contamination within the control zone include city streets, storm and municipal sewer lines, and several school related buildings. It is advisable for the school to restrict use of fertilizers, pesticides, herbicides, and other chemicals and the washing of fertilizer and pesticide application equipment near the well. The inventory region for the well includes three above ground fuel storage tanks and a relatively small percentage of agricultural land where fertilizers and ag-chemicals could be used. Within the recharge region there are also multiple inactive underground fuel tank sites, petroleum release sites, and small gravel pits listed for the vicinity of Rosebud but the exact locations are unknown. Land use in the recharge region and surface water buffer regions includes relatively 3 small percentages of agricultural land. Significant potential contaminant sources within the recharge region, like irrigated ag-land, may still pose a threat over time, they are not included in the susceptibility analysis in this report. Possible management options however are included at the end of this report. The susceptibility