Yuma Ag and You: Consider first the soils that you build on!

Bobbi Stevenson-McDermott      January 22, 2017 publication

One of the advantages, in my mind, to living somewhere for almost 50 years is the accumulation of historical knowledge about your county. Since I spent 38 years working with growers on soil, water and cropping improvements, I’ve seen a lot. It has always amazed me that many issues that are part of the natural resource base that we deal with every day are seemingly given so little attention.

The paper recently outlined a proposed development of a university on lands in the North End of Yuma. The first thing I thought of as I read the article is the soils in the area and the presence of a high water table Heading west on Giss Parkway approaching the entrance to the Yuma Territorial Prison is a pool of water on the south side of the road. That standing water is the existing water table in the area. It is important to remember that the Colorado River is presently at its lowest point during the year and that there are no flows in the Gila River adding to the water in the Colorado. Since 1993, there have been no significant, extended flood flows on the Colorado River or Colorado River. In my time in Yuma, there have not been floods on both the Colorado and Gila Rivers at the same time.

Just considering the effects of high water table on public works and infrastructure, some of the problems encountered included flood waters seeping into the storm sewer pipes reaching nine blocks south of the river overnight. The main pumping station for the city’s wastewater treatment plant partially caved in at Ave C and 3rd Street due to rising ground water. 250 to 300 riverside residents were forced from their homes by seepage through the levees and rising groundwater. Rising ground water coming up under the valley roads caused cracking and damage to the roadways.

The water table today is probably as low as it has been in decades due to the drought years, but it will rain again someday. Work that is occurring along Interstate 8 at the check station is requiring the pumping of groundwater to achieve their objectives. When the businesses along Redondo Drive were built, many had to have dewatering pumps working so that necessary infrastructure could be installed.

Some of the soils being looked at for development are heavy clays in texture and will act as sponges, swelling when wet and shrinking when dry. While this is not a problem for farmlands, the shrink-swell actions will crack foundations, walls, disrupt buried pipes and conduits; as well as cracking driveways and sidewalks. Buffering these soils with several feet of sand before construction can reduce all these problems by allowing the building to float on the inert sand.

The Bureau of Reclamation maps the depth to groundwater on a monthly basis and also has historic records which show what the groundwater levels were during flood flows on the Colorado and Gila Rivers. The Natural Resources Conservation Service has extensive soils information as well as engineering and construction rating for the local soils. Long time residents have seen the same problems and repairs occurring on certain sewer collector lines, intersections and roadways. It would seem valuable for those in the development business of any type to utilize the historic and institutional knowledge of the natural resources in Yuma County to make best use of the dollars expended. As the old saying goes, ‘fool me once, shame on you; fool me twice, shame on me’.