Ft Bayard Irrigation Water Use Calculations.pdf

Fort Bayard National Cemetery Irrigation Water Use Calculations

The purpose of the irrigation water use calculations contained in this report is to confirm the size of the water service line that is planned to replace the existing water service to the cemetery. The following calculations are based on a review of the Record Drawings for the Ft. Bayard National Cemetery, Cemetery Improvements Project (#885CM3007B) dated April 14, 2016 and prepared by VCI.

Existing Conditions

The existing site is approximately 19 acres in total. Approximately 450,000 SF (10.33 acres) is currently irrigated turf grass. The Master Plan for the full buildout of the site which was completed in 2010 by

URS and MRWM includes an additional 50,000 SF of irrigated turf proposed for the southernmost portion of the site. The total of irrigated turf at full buildout will comprise 500,000 SF (11.48 acres).

The existing water service line that feeds the cemetery is a combination of an above ground 4” HDPE pipe and 4” DIP pipe that runs from the elevated water tower located approximately 1,000 feet to the northeast of the cemetery.

At the eastern cemetery boundary the 4” line runs into a water meter vault before the line is split between the domestic service to the buildings and the irrigation service. The irrigation service includes a 3” RPBA backflow preventer and booster pump that were installed as part of the 2016 Cemetery

Improvements project (#885CM3007B). In addition, a complete irrigation system was installed throughout the cemetery. The irrigation system is composed of 4” mainline with a maximum recommended flow capacity of 200 GPM to remain below a maximum velocity of 5 feet per second. The booster pump is also capable of providing a maximum flow of 200 GPM.

Irrigation Water Use Estimates

Conservative estimates of irrigation demand for the cemetery can be calculated based on the amount of turfgrass to be irrigated and the peak season irrigation requirement (in inches). At full buildout, there will be approximately 500,000 SF of irrigated turf grass. Peak irrigation demand occurs during the month of June in Fort Bayard, NM when the Evapotranspiration (ET) rate is 9.64” inches per month

(source, EPA Watersense: https://www.epa.gov/watersense/water-budget-data-finder). 9.64” per month is equivalent to 0.32” per day or 2.249” per week.

For a conservative approach to sizing the irrigation supply, we can assume full ET replacement would be required. Based on a five day irrigation schedule, the total peak season daily irrigation demand is 0.45”

(2.249”/5 irrigation days ) or 0.0375 feet per day.

Therefore if we apply 0.0375 feet of irrigation over 500,000 SF of turf per irrigation day, we will require

18,750 cubic feet or 140,250 gallons of water per irrigation day. Assuming a 12 hour water window

(7pm to 7am), the peak irrigation demand is approximately 195 gallons per minute.

Based on our calculations, we recommend the water supply line be designed for a capacity of 200 gallons per minute in order to meet the peak season demand for irrigation. This is a conservative water use estimate based on the maximum amount of water needed to water the entire cemetery in one night, but is consistent with other similar sized sites we have worked on for the NCA.

Estimated annual irrigation requirements for the turf grass are based on application of approximately

40” (3.33’) of irrigation water on average per year. Based on this application amount, the anticipated annual water usage can be calculated as follows:

500,000 SF of turf x 3.33’ of irrigation x 7.48 gallons/CF = 12,454,200 gallons per year (approximately

38.22 acre-feet)

Other Considerations

In addition to irrigation, the water supply that feeds the cemetery also supplies domestic water to the existing PIC and Maintenance Buildings. The demand for these buildings should be negligible compared to that of the irrigation demand, but should be factored into the sizing of the water supply.

There does not appear to be a fire hydrant connected to the existing water service line, however one was contemplated in the original phase 1 design dating to 2011. If a fire hydrant connected to the new service line is anticipated to be provided in the future, the requirements for demand should be taken into consideration in sizing the new service line.

There is also an existing fire hydrant located adjacent to the one story building near the existing water tower and chlorinating tank that appears to be fed from this same supply line. This hydrant appears to be upstream from where the new water line connection is being made. Whether this hydrant remains active or requires a larger line size is unknown, but should be taken into consideration when sizing the supply line to the cemetery as well.