Greening-aiken/Data Collection

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There were two main pieces that we needed to look at in order to estimate the feasibility of this project. We had to identify how much potable water the Aiken Center uses to flush the toilets, and then calculate the amount of water that could be collected through the green roof. With these two pieces of information, we could estimate the amount of potable water that could be saved by implementing a stormwater as greywater system.

We ran an analysis with the School Dude website and in 2017 the Aiken Center used 277527.292 gallons of water. This is the total amount of water used through all processes in the Aiken Center. The raw data and a couple simple analyses are included in the file below.
File:Water and Sewage CF and Gallons 2013-2017.xlsx

From this, we had to figure out how much potable water of the total was being used to flush the toilets. In order to do this, we obtained room usage data for Spring 2018 from the Aiken Center office and calculated how many people were in each class on each day. Our total number of people at "peak period" (highest number of people in the building on a given day) was 857 on Tuesdays. Our average of every week day was 708 students. We also obtained the number of graduate students and faculty/staff and calculated the corresponding number of full-time employees from that. The FTE calculation is used by LEED in many of their estimations in order to quantify the use of various types of resources. There were 64 faculty and 46 graduate students in the Spring of 2018. The data and corresponding calculations are included in the file below.
File:Room usage.xlsx

Prior to the Aiken Center's renovations in 2012, LEED formed a similar calculation using a model and rough estimates. However, the actual water use has far surpassed their predictions. One reason for this appears to be that they estimated that the number of people in the building at peak period was 300, with an average of 221 people on a given day. Their estimate is below.

File:LEED Occupancy Calculations.pdf

We decided to use a similar model as LEED to calculate number of gallons of potable water that was used to flush the toilets. Using the obtained data of the room usage and number of employees in 2018, we began to estimate the number of people that would be in the Aiken Center on a given day. We did this by classifying 6 different day types: academic days, academic weekends, holiday days, holiday weekends, summer days, and summer weekends. Each day type was assigned a corresponding number of transient users (students) and FTEs (Full-Time Employees) based on the real data.
In our formula to predict gallons of toilet water used, we used the following assumptions:

  • 50% ratio of males/females
  • Equal bathroom usage among males and females
  • Transients use the bathrooms 50% of the time that they are in the building
  • FTEs use the bathrooms 3 times throughout the course of the day
  • Males use the urinals around 20% of the time that they use the bathroom
  • Toilets use 1.6 gallons per flush and urinals use .5 gallons per flush (listed on facilities)

With these assumptions, we calculated the number of gallons of water used to flush the toilets on each day type. We then multiplied this by the number of each type of day in a calendar year and found that the Aiken Center was using around 132,283 gallons of water annually to flush the toilets in 2018. The data and calculations are included in the file below.
File:Water Used to Flush Toilets.xlsx

Given that the building used a total of 277527.292 gallons of water total, this means that around 48% of total water usage was going towards flushing.

We also had to figure out how much stormwater we would be able to collect and use. The green roof has data from 2014 of volume of water that has passed through. However, only 9 months of data are available for the year of 2014 because of a tragic mishap in which the data logger was stolen. Because of this, we had to use data from Burlington Airport's weather website and extrapolate using a linear regression model and the data that we already had from the 8 watersheds. There are also parts of the roof that are not currently being monitored. Using Google Earth, we measured the area of the 2 uncovered spots to be around 265.33 square meters. The total area of the eight current watershed treatment zones totaled 999.20 square meters. The total roof area measured equals 1,264.53 meters squared.

62.06 (back entrance) + 203.27 (front entrance) = 265.33 m^2 + 999.20 m^2 = 1,264.53 m^2