Water Use at Minnesota Rest Areas: Task Report

Abstract

The Minnesota Department of Transportation (MnDOT) State Wide Rest Area Program is composed of a coordinated system of public rest areas and waysides, intended to help motorists travel safer. In 1979, MnDOT collected data at rest areas to refine assumptions and improve techniques for design of rest area water supply and sewage treatment designs. They found on average that with water conserving devices people used 2.8 gallons, while non-water-conserving devices used 4.5 gallons. This study evaluated the accuracy of MnDOT design charts and formulas based on people counts and water flows. A total of twelve rest areas were included in the study. Data was collected from Spring 2015 to Fall 2016. Site specific average water use per person ranged from 0.9 gallons to 4.6 gallons. A difference was found between the two building types, interstate and non-interstate, with interstate visitors averaging 2.2 ± 0.5 gallons and non-interstate visitors averaging 1.8 ± 0.7 gallons. The difference between building types was not easily explainable, however it is theorized fewer visitors at non-interstate sites results in less water needed for cleaning or water treatment. The results of this study indicate that the original design values are still valid. However, due to the wide variation of water use per site, maximum water demands and usage trends should be estimated when designing a new septic system to ensure the most appropriate septic system is installed, resulting in the successful treatment of waste water and the fulfillment of expected system lifespans without additional maintenance costs.