1. Rainwater Conservation System Town of Cary Senior Center Facility

2. 17,000 sq. ft $2.5 Million

3. Water Use Courtyard Irrigation

4. Lake System 3 Ballfields - 3.5 ac Bond Lake - 50 ac

5. Senior Center Layout Garden Plots & Lawn 10,000 sq. ft. 90 GPM Pump Tank 1200 gal 15 GPM

6. Modifications 1. Direct rain gutter downspouts into tanks. 2. Increase tank size to allow for rain storage.

7. Collection & Storage Storage - 2 Tanks, 6000 gals total Collection - Gutter system

8. Distribution Pump system & Piping system

9. Averaged Rain Supply and ‘Rule of Thumb’ Irrigation Demand Average Weekly Rain Supply: Roof = 3250 sq.ft.; Rain = 0.9 in.; Efficiency = 75% Yield = 1,400 gals./week Average Weekly Water Demand: Garden = 10,000 sq.ft.; Irrigation = 1 in./wk.“rule of thumb” Demand = 6,400 gals./week - Supply = 22% of Use. Other 78% requires other sources. - Note an average 0.9 inches of rain also fell on garden.This exceeds the needed 78%. - So in theory, Conserved Rain satisfies the Demand deficit.

10. Supply & Demand: No Rain Scenarios Design for periods of no rain / no collection: Provide storage/supply capacity for 3 weeks no rain 3 weeks Demand = 19,200 gals (@ 1 inch/week) 3 weeks Supply = 25,600 gals (19,200 gals / 0.75 efficiency). Current system Storage: 2 tanks - 6,000 gals - Supply capacity is inadequate. - Alternate water source, increased collection surface and/or increased storage is required.

11. Potable Water Demand Reduction Current system inadequate to meet full demand. At 75% efficiency, system still reduces potable water demand by an average 1,400 gals./week or 200 gals per day. Average annual irrigation weeks = 34 weeks Average reduced potable water demand = 47,600 gals / yr (1,400 x 34 wks)

12. Cost Recoup: Reduced Potable Water Purchase Net cost for potable water = $4.51 / Kgal (Typical potable water rate + O&M = $4.46 + $0.05) Average potable water saving = 47,600 gals/year Reduced potable water costs = $215 / yr ($4.51 x 47.6 Kgals) Rainwater system cost $7,250. Recoup of system costs in 7,250 / 215 = 34 years

13. Cost Recoup: Potable Water Purchase Eliminated Net cost = $4.51 /Kgal Full season irrigation demand = 218,000 gals/year (10,000 sq.ft. @ 1 in/wk for 34 weeks) Reduced potable water costs = $983 /yr ($4.51 x 192 Kgals) Expanded system cost = $31,175 –4.3 factor size increase to meet 3 week drought. –Economies of scale ignored Recoup of system costs in 31,175 / 983 = 32 years

14. Lake System Cost Recoup: Potable Water Purchase Eliminated The lake supplies irrigation water for 8.5 acres (ballfields). Irrigation averages 1 inch or 231,000 gals per week for 27 weeks. Yearly water demand = 6,231,000 gals per year Potable water costs savings = $28,100 year (6,231 Kgals x $4.51) Lake system costs $163,600 to construct. Recoup of system costs in 6 years (163,600 / 28,100 per yr.)

15. Cost Recoup: Deferment Basis Estimated yearly deferment value of reduction in town peak day potable water demand = $0.25 x gals of daily reduction. Basis: estimate of deferment value for Town of Cary water treatment facility expansion and O&M. Value does not include certain external benefits. Example, value of reduced stormwater management. Rain system reduces peak demand 200 gals/day. Yearly deferment value = $0.25 x 200 = $ 50 Construction of the rainwater system cost $7,250. Recoup of system cost in 145 years ($7,250 / $50)

16. Cost Recoup: Meeting Full Demand Full system demand = 218,000 gals/year (238 days demand) System reduces town peak demand = 916 gals/day Yearly deferment value = $0.25 x 916 = $229 Expanded system cost = $31,175 –4.3 factor size increase to meet 3 week drought. –Economies of scale ignored Recoup of system cost in 140 years ($32,250 / $229 per yr.) - Economies of scale should decrease recoup time.

17. Lake System Cost Recoup: Deferment Basis Yearly water demand = 6,231 Kgals per year Irrigation season is 190 days (7x27) Deferred potable water production = 32,800 gal/day. (6,231 Kgals / 190 days) Yearly deferment value = $8,200 (32,800 x 0.25) Lake system costs $163,600 to construct. Recovery of system cost = 20 years (163,600 / 8,200 )

18. Alternative to Storage Tanks Create water storage ponds. Or Combine irrigation water storage with stormwater retention. May lower costs, improve payback & add amenity value

19. Other Benefits of Rain Conservation Systems Conservation of potable water supply source Contributes to stormwater management –Reduced runoff peak volume –Increased land treatment of runoff Value of irrigation of landscaping when strict potable water conservation measures are in effect Value as a public education tool