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William Hahn, P.G. Professional Hydrogeologist 6589 Elaine Road, Evergreen CO 80439

Presentation to the Jefferson County Board of County Commissioners April 16, 2019 Conifer Heights Rezoning Request 18-107113RZ. William Hahn, P.G. Professional Hydrogeologist 6589 Elaine Road, Evergreen CO 80439. Credentials - Basis for my Professional Opinions.

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William Hahn, P.G. Professional Hydrogeologist 6589 Elaine Road, Evergreen CO 80439

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  1. Presentation to the Jefferson County Board of County CommissionersApril 16, 2019Conifer Heights Rezoning Request18-107113RZ William Hahn, P.G.Professional Hydrogeologist 6589 Elaine Road, Evergreen CO 80439

  2. Credentials - Basis for my Professional Opinions • B.S. Geology Additional Studies in Hydrology , Numerical Modeling • Practicing Hydrogeologist with >45 Years Experience • Expert Witness-State Water Courts-Federal District Court-US Supreme Court (KS v CO) • Published Papers on Fractured Crystalline Rocks • Design, Construction, and Testing > 250 Water Supply Wells • Research, Design, and Testing of Facilities for Recharge of Treated Wastewater

  3. Principal Findings • Investigations flawed • Design was based on “averages” -Size of development (# units) overestimated -Required capacity of on-site wells underestimated • Failed to demonstrate adequate on-site water supply • Risk to quality of water supply (on-site disposal of treated wastewater) • Long-term sustainability of the water supply for this development has not been proven These all point to a water supply that could fail! Further discussion provided in my letter report of April 10, 2019

  4. Example: What is the Required Well Capacity? (how many wells and how much they will produce) Applicant: “…gross demand rate of just under 9 gpm…” “…drilling of up to 8 wells should produce sufficient water…” Analysis was based on “average” use. We can’t count on daily water use to always equal (and not exceed) the average. We can’t count on annual water use to always equal (and not exceed) the average.

  5. What is the Required Well Capacity? Preferred approach: 1) if we adopt the Applicant’s number of 137 gpd/unit 2) introduce a margin of safety of 1.5 (range 1.5 to 2.5) 3) we have: 137 gpd/unit x 1.5 = 206 gpd/unit For 101 units we need: 206 x 101 = 20,800 gallons per day = 14 gpm (not 9 gpm as claimed)

  6. Perspectives on Supply My Well (#145043) 3.5 gpm Village at Elk Crossing 10 – 46 gpm Formal Well Test Well 1 (72 hours) 10 gpm, 86 % of water in well still available

  7. What Can the On-Site Wells Produce? Well 1 (Existing House Well on Property) “…can hold a pumping rate of 1.5 gpm for 8 hours” (then what?) Well 3 No formal testing <0.5 gpm? Well 4 tested for < 4 hours <1.7 gpm? Conclusion: Well testing was completely inadequate .

  8. Risk to Water Quality Capture of Wastewater by On-Site Wells SupplyWell SupplyWell Exfiltration Gallery Infiltrating Wastewater Groundwater Moving to Wells

  9. Summary • Flawed investigations (methods and conclusions) • Size of development (101 units) is overestimated • The need for on-site water supply (wells) is underestimated • The ability to develop the needed water supply has not been demonstrated • Significant risk of shortfall in supply • Significant risk that the on-site supply will be degraded by on-site wastewater disposal • Sustainability of supply not proven • Need for more aggressive review by JeffCO Thank you

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