1. Planning Commission Presentation January 25, 2008 David Conway, REHS Mariposa County Health Department

2. Water, Where does it come from and how do we protect it? What is an aquifer? Where are the aquifers in Mariposa? Different types of Wells –Valley Aquifer drilling/digging –Mountain Hard rock drilling – fracture systems vs. open aquifer Well construction for hard rock wells –Casing to rock then open hole –Sealing wells Static Level Wells are two way Conduits Contaminates associated with Poultry operations and their fate in the environment Controlling the spread of contaminates Protecting the public health

3. Aquifers What is an Aquifer? –A layer of permeable rock, sand, or gravel through which ground water flows, containing enough water to supply wells and springs.

4. Two types of Aquifer Alluvial and Fracture Alluvial basins usually provide easy targets for well locations. Fracture flow aquifers, on the other hand, can pose problems for well locations. A good analogy is a bathtub full of sand and water. Placing a well anywhere in the tub will give you water in the same abundance and at the same level. An equivalent analogy is the same bathtub full of carefully and tightly stacked bricks, again with water at the same level. Placing a well in the brick-filled tub will produce water, if and only if, the well penetrates a joint between bricks (the equivalent of a fracture in bedrock).

6. 120 41 140

7. Yosemite Valley Aquifer

8. Fractured Rock Aquifers Water is trapped in fractures in the rock. Different Types of rock have different fracture patterns –Some have wide fractures that hold a lot of water (Example Granite) –Some have narrow, tight jointed fractures that do not hold very much water at all. (Example Greenstone) Fractures are not consistent throughout the rock; therefore, two wells very close to each other can have widely varying yields and quality.

9. Fractured Rock

10. Similar wells can have varied yields in fractured rock aquifers

11. Domestic Well Construction 6 inch well casing 10 inch bore hole to rock Casing into rock Sealing material between casing and bore hole

12. Static Level

13. Conduit for Contamination Contaminated water Uncontaminated water

14. Contaminates associated with Poultry operations and their fate in the environment Bacteria –Mostly coliform bacteria –Possibly salmonella Nitrates

15. Contaminates associated with Poultry operations and their fate in the environment Bacteria are present in the environment and naturally die off over time Not a problem if they don’t get into the water or food supply If they do sanitation can be necessary disinfectant or boiling

16. Contaminates associated with Poultry operations and their fate in the environment Nitrates Great as fertilizers but they do not breakdown very easily in the environment They dissolve in water and are carried with the ground water flow DO NOT BOIL

17. Controlling the spread of contaminates Contain the material to prevent it from being washed into surface water sources or dissolving into ground water Locating operations that have a potential for contamination far away from drinking water sources. (Setbacks) Proper well construction to prevent surface and undesirable subsurface water contamination.

18. Protecting Public Health Proper well location Verify that the location meets all setbacks from sources of contamination Seal requirements in the well ordinance –In some cases special conditions are placed on construction permits for deep seals and testing. Treatment Systems with maintenance contracts

19. SUMMARY We covered what an aquifer is. The two types of Aquifers we have and where they are in Mariposa? Different types of Wells fracture systems vs. open aquifer Well construction for hard rock wells The importance of Sealing wells Static Level Wells are two way Conduits Contaminates associated with Poultry operations and their fate in the environment Controlling the spread of contaminates Protecting the public health

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