Big Sky Wastewater Facility Plan Update Final Report August 25, 2015

Updated Projected flow Flows updated to include LMM and Spanish Peaks

Growth Projections High rate 4.82% Average rate 4.09% Low Rate 3.36 %

Calculated irrigation Disposal capacity (Million Gallons per year) Prior Calculated Capacities Revised Capacities Meadow Village Course 206* 140-160 YMC** 76 22-28 Spanish Peaks** 100.8 20-30 Total 382.8 182-218 YMC and Spanish Peaks based on preliminary design reports completed by Nicklin Earth and Water Maybe high based on actual irrigation volumes currently being used * Per DEQ approval ** Based on Design Reports

REASONS FOR DIFFERENCES Percolation rates used Spanish Peaks = 0.2 inches/hour (Based on SCS data) YC = 2.0 inches/ hour (Based on SCS data) Meadow Village = 1.58 inches/ hour (Based on perc tests) Nitrogen uptake Spanish Peaks= 178.4 pounds/ acre YC= 147 pound/acre Meadow Village 108 pound/acre ( from irrigation) Irrigation Period Spanish Peaks and YC used 24 hours/day Meadow Village used 6 hours/day 137 day growing season used for all three courses Spanish Peaks and YC perc rates based on SCS published data. No percolation testing has been done on YC or Spanish Peaks to confirm Irrigation Period; need to have a 3:1 dry- wet cycle to meet DEQ requirements. SP and YC calculation done using 24 hour per day All courses use a 137 day irrigation period. It is unlikely that SP and YC would have the same irrigation period as the Meadow Village

Growth Projections 218 MGY 182 MGY High rate 4.82% Average rate 4.09% Low Rate 3.36 % 182 MGY

Golf course Upgrades and recommendation Do testing on the YC and SP courses to determine actual percolation rates

Storage requirements no winter disposal

Existing storage Meadow Village Yellowstone Mountain Club Large Pond = 60.1 MG Small Pond = 19.6 MG Total Filtered Storage = 79.7 MG SBR Effluent = 8.2 MG ( but effectively zero due to piping) Yellowstone Mountain Club 80 MG Total Existing Storage = 159.7 MG

Existing & Future storage Meadow Village Large Pond = 60.1 MG Small Pond = 19.6 MG SBR Effluent = 8.2 MG (with piping change) Total Storage = 87.9 MG Yellowstone Mountain Club Existing = 80 MG Future = 50 MG Total Storage = 130 MG Grand Total Existing and Future = 217.9 MG Storage Needs (no winter disposal)= 226 MG

Storage requirement with winter disposal 100,000 gallons per day of winter disposal

Need for Project Projected Flows exceed current disposal capacity by 95.8 to 131.8 MGY Reduce the level of nutrients applied to the Meadow Village Couse to reduce impacts to the Middle Fork Provide additional disposal to allow the District to exercise its water right on the West Fork. Current disposal is 95.8 to 131.8 MGY short of the projected full buildout flows

Alternatives considered for additional Disposal 1. Disposal on the west side of the Madison Range near Ennis. Estimated Cost $13.1 million 2. Construct purple pipe system for effluent reuse in Meadow Village area. Estimated Cost $5 million + treatment plant upgrades. Could also be part of an expanded golf course irrigation 3. Indirect Potable Reuse Deep Injection Wells (not considered viable) Shallow injection Wells ( rough estimate $350,000 to $500,000 + advanced treatment $7-$9 million) Additional study would be required to determine the actual volume that could be injected

Alternatives considered for additional Disposal 4. Subsurface Disposal (drainfields) 5. Surface Discharge to the Gallatin River during the winter 6. Snowmaking 7. Direct Potable Reuse

Winter Disposal Options Subsurface drain fields or aquifer injection Indirect Potable Reuse Unlikely to meet all discharge needs Aquifer injection- must meet primary drinking water standards or non-degradation requirements at discharge point Additional treatment required Surface discharge Possible based on DEQ rules and non-degradation criteria

Existing treatment plant Plant Capacity Effluent Quality Metering Additional Process Monitoring Ammonia and ORP probes for SBR’s and digesters TSS meter for waste sludge to help control solids in system Adding VFD’s to blower motors to control DO

Plant Capacity Design Capacity – Peak Day 1.3 MGD Current Capacity – Peak Day 1.04 MGD Cycle time increased to improve nitrogen removal Current Peak Day 0.923 in 2014 but has been around 0.7 MGD in prior years Third basin needed by 2021, start planning by 2018. Total cycle time = 4.8 hours React 0.58 hours Mixed fill 0.67 hours Settling time 0.75 hours React fill 1.74 hours Decant time 1.07 hours Total cycle time = 6 hours React 1 hour Mixed fill Settling time React fill 2 hours Decant time

Effluent Quality

Cold Weather impacts Improved monitoring for solids control.

Aeration control

Metering

Metering

Treatment plant upgrades Add VFD drives to blowers $216,000 Modify piping for SBR effluent storage pond $187,000 Additional monitoring probes District has already purchased Additional work to resolve metering