Sun Valley Water & Wastewater Project
Research
Soil Conditions
Research began with evaluating site conditions and client plans, expectations, needs, and resources to determine which water supply and wastewater systems would be most suitable. The following sections provide the research findings.
The United States Department of Agricutlure Custom Soil Resource Report (pg.12) indicated that approximately 80% of the soil was Grieta sandy loam with 1 to 3% slopes. Also, this report indicated that the soil is well drained, meaning that the permeability was suitable for an onsite wastewater treatment system. This sandy loam soil would be appropriate for septic system because sandy soils (that are not too coarse) are desirable for septic systems [1]. The depth to bedrock is another characteristic that can be a severe problem if it is under 40 inches [2]. A map overlay in the Esri ArcGIS (geographic information system) provided by the US Natural Resources Conservation Service showed that the depth to the bedrock for the site is only approximately 0-20 inches, and therefore would require additional drilling to be suitable for a septic system [3].
Water Supplies
Approximately 61% of the population within this region relies on groundwater as their main source of water [4]. The nearby cities of Holbrook and Winslow receive their water solely from groundwater that is pumped from the C-aquifer [4]. The area (Township 18 North and Range 22 East) that Sun Valley Ranch is located in has scattered wells that are mostly exempt according to Arizona Department of Water Resources. An exempt well has a maximum pump capacity of 35 gallons per minute and is typically used for smaller residences [5]. An analysis, on the water level for wells near Sun Valley Ranch was determined using the ADWR well registry. This indicated that 4 of the 19 wells within the Sun Valley Ranch area are dry.
Alternative Wastewater and Water Supply Systems
Due to the client’s preference for nonconventional systems, the team researched alternatives for both the wastewater and water supply systems to determine if they would perform effectively in Sun Valley.
Water Supply Systems
The alternatives for water supplies near the Sun Valley Ranch included connecting to Holbrook’s water supply, an on-site well, or importation from Holbrook. Over 10 miles of piping would be required to connect Sun Valley Ranch with Holbrook’s water supply system and therefore it was not considered a feasible alternative. Although the on-site well would be expensive, the importation alternative would involve annual transportation costs, so these two alternatives were compared
Wastewater Systems
The following wastewater systems were considered by the team as possible sources of secondary treatment for the site’s wastewater. These include the on-site wastewater systems defined by ADEQ that have flows less than 3000 gallons per day.
- Activated sludge and aerobic system
- Constructed wetland, land treatment, and stabilization pond
- Peat filter, textile filter, trickling filter, and intermittent sand filter
- Evapotranspiration bed lined or with a natural seal, gravelless trench, engineered pad, sand lined trench, nitrate reactive media, and cap system
- Septic tank, sewage vault, and Wisconsin mound
- Subsurface drip irrigation and surface disposal
- Composting
Most of these systems were too expensive or they would function more effectively for a larger population. The team determined that the wastewater system alternatives that would be most suitable for the Sun Valley Ranch consisted of stabilization ponds, a septic tank, and composting toilets.
References:
[1] P. Kiely. (2014). What is Good Soil? What is Bad Soil for Septic Systems? [Online].
Available FTP:http://islandwatertech.com/blog/
[2] U.S. Natural Resource Conservation Service. (1996). Natural Soil Limitations for Septic
System Installation and Operation. [Online]. Available FTP:
http://www.montana.edu/uessc/SepticAssessment/soilratetbl.htm
[3] ArcGIS. Bedrock Depth- Minimum (beta). [Online]. Available FTP:http://www.arcgis.com/home/webmap/viewer.html?webmap=7498b9f186bc4a2a9fee6c85d8
63f3b6
[4] Arizona Water Atlas: Volume 2, Eastern Plateau Planning Area [Online]. Available FTP:
http://www.azwater.gov/AzDWR/StatewidePlanning/WaterAtlas/documents/Volume_2_final_web.pd
[5] Arizona Department of Water Resources. A Practical Guide to Drilling a Well in Arizona.
[Online]. Available FTP:http://www.azwater.gov/azdwr/PermitsFormsApplications/documents/wellguide.pdf
