Cost Estimations
According to the University of Houston's website, the university has about 650 acres of landscaping area, which translates to about 28,310,000 square footage. It is suggested that all this area is watered once a week, during which approximately 1 inch of water should be applied to the area. According to the Association for the Advancement of Sustainability in Higher Education (AASHE)'s Sustainability, Tracking, Assessment and Rating System (STARS) report, the University of Houston uses about 360,000,000 gallons of regular water and about 340,000,000 gallons of sewer water (18). Sewer water is not typically used for irrigation as it could be harmful to crops and landscape. Of the total 360,000,000 gallons of regular water used in 2015, about 25,000,000 was used for non-potable uses (18). Since irrigation water is non-potable due to contamination, we will assume that the university uses this amount for irrigation in a full performance year.
Based on the information highlighted in our "Fiscal Analysis" section, we discovered that our proposed plan will produce about 12,500,000 gallons of harvested water for the university to use for irrigation purposes throughout the year. Since that is the case, we can use this information to estimate the size of the tank needed to store the harvested water. Figure 1 illustrates the bi-weekly and monthly average of water harvested from the three systems.
Based on the information highlighted in our "Fiscal Analysis" section, we discovered that our proposed plan will produce about 12,500,000 gallons of harvested water for the university to use for irrigation purposes throughout the year. Since that is the case, we can use this information to estimate the size of the tank needed to store the harvested water. Figure 1 illustrates the bi-weekly and monthly average of water harvested from the three systems.
In order to meet irrigation needs on a weekly basis, all of this water will be put to use. Thus, we can save money by building a smaller tank that supports the specific amount of water needed bi-weekly instead of monthly.
According to multiple sources, most rainwater harvesting projects cost anywhere between $1.50 and $2.00 per gallon (19). Based on our findings, we calculated a cost estimate in order for the university to fulfill this project. The estimated cost range of the three systems using the bi-weekly estimate is shown in the table below:
According to multiple sources, most rainwater harvesting projects cost anywhere between $1.50 and $2.00 per gallon (19). Based on our findings, we calculated a cost estimate in order for the university to fulfill this project. The estimated cost range of the three systems using the bi-weekly estimate is shown in the table below:
The difference in cost can depend on multiple factors such as materials needed to build the tank, pipes, gutters, filters and first-flush diverter. However, most of the cost difference is dependent on the location of the tank: in-ground or on the surface (19). High initial costs will be offset with savings over time, and the high savings come into play as evidence of a self-offset project. Funding possibilities are explained in the following section.
Funding
The State of Texas has rainwater harvesting laws that call for an energy savings performance contract in order to fund such a project at an institution of higher education such as the University of Houston. Texas defines this contract as a contract "for energy or water conservation measures to reduce energy or water consumption or operating costs of new or existing institutional facilities in which the estimated savings in utility costs resulting from the measures is guaranteed to offset the cost of the measures over a specified period” (8). Section 51.927 of the legislature goes into detail about the requirements of such contract and the more important provisions are highlighted below:
The contract clearly states that the university can only enter such a contract if the project's estimated savings will offset its cost in 20 years or less. If the institution were to provide enough proof of its savings over a 20 year span, then a bond will be provided to the institution to move forward with its project. Additionally, the university is not limited to the budget given and is allowed to increase the budget with already existing institutional funds if need be.
- Before entering into an energy savings performance contract, the board shall require the provider of the energy or water conservation measures to file with the board a payment and performance bond in accordance with Chapter 2253, Government Code. The board may also require a separate bond to cover the value of the guaranteed savings on the contract.
- The board may enter into an energy savings performance contract for a period of more than one year only if the board finds that the amount the institution would spend on the energy or water conservation measures will not exceed the amount to be saved in energy, water, wastewater, and operating costs over 20 years from the date of installation.
- An energy savings performance contract may be financed:
- Under a lease/purchase contract that has a term not to exceed 20 years from the final date of installation and that meets federal tax requirements for tax-free municipal leasing or long-term financing, including a lease/purchase contract under the master equipment lease purchase program administered by the Texas Public Finance Authority under Chapter 1232, Government Code;
- With the proceeds of bonds; or
- Under a contract with the provider of the energy
- Notwithstanding other law, the board may use any available money, other than money borrowed from this state, to pay the provider of the energy or water conservation measures under this section, and the board is not required to pay for such costs solely out of the savings realized by the institution of higher education under an energy savings performance contract.
The contract clearly states that the university can only enter such a contract if the project's estimated savings will offset its cost in 20 years or less. If the institution were to provide enough proof of its savings over a 20 year span, then a bond will be provided to the institution to move forward with its project. Additionally, the university is not limited to the budget given and is allowed to increase the budget with already existing institutional funds if need be.
Project costs
After analyzing the initial costs and savings of our rainwater harvesting project, we deduced an approximate cost of all three rainwater harvesting systems. The results are shown in the table below.
The total cost of the project ranges from $766,500 to $1,022,000. Based on our findings in our "Fiscal Analysis" section, we deduced that in perfect conditions, the University of Houston would save about 12,289,584 gallons of water priced at $4.20/1000 gallons. This amounts to about $51,616 saved in a full performance year. The timeline for when the projects savings will offset their cost is shown in the graph below:
Based on Figure 3, if the university chooses the lower rate ($1.50/gallon), its savings will offset the cost approximately 15 years after final installation. If the university ends up paying the higher rate ($2.00/gallon), it will take the full 20 years to offset its cost. In both cases, the University of Houston would be fulfilling the terms of the contract with the state of Texas. Due to its economic feasibility, the implementation of an on-campus RWH system should be highly considered.
Finally, the University of Houston can take steps to reduce initial costs and increase its offset rate faster than the 15-20 year range. The most significant action the university can take to alleviate costs of construction is to reduce the size of the tank. By obtaining a tank large enough to hold about a week's worth of harvested water rather than the bi-weekly one proposed, the university can reduce project costs considerably. Additionally, the university could opt to construct the storage tank at the surface instead of in-ground to further reduce cost. These cost reduction strategies are powerful steps the University of Houston could take to highlight its advantages, substantially increase its savings rate and make the overall project more appealing to the board.
Finally, the University of Houston can take steps to reduce initial costs and increase its offset rate faster than the 15-20 year range. The most significant action the university can take to alleviate costs of construction is to reduce the size of the tank. By obtaining a tank large enough to hold about a week's worth of harvested water rather than the bi-weekly one proposed, the university can reduce project costs considerably. Additionally, the university could opt to construct the storage tank at the surface instead of in-ground to further reduce cost. These cost reduction strategies are powerful steps the University of Houston could take to highlight its advantages, substantially increase its savings rate and make the overall project more appealing to the board.