Vadose Zone Hydrology
DBS&A is distinguished by an established expertise in vadose zone processes. The vadose zone is the area between the ground surface and the water table and is comprised of rock and soil; it plays a vital role in groundwater replenishment and groundwater quality protection. The vadose zone is particularly important in the western United States, where there is sometimes a deeper water table, and therefore a larger vadose zone that may substantially influence natural recharge of groundwater, as well as contaminant transport.
Water may move through the vadose zone in a counterintuitive fashion. In some instances, under unsaturated conditions, water will preferentially flow through the finer-textured soils. There can also be considerable lateral water movement in an unsaturated condition where complex stratigraphy exists. These flow phenomena are controlled by the soil water characteristic and hydraulic conductivity properties of the various soil layers. These properties can be quantified through laboratory and field tests and incorporated into models to predict the direction and rate of water movement.
DBS&A has completed many challenging vadose zone projects, from modeling fate and transport of contaminants through fractured volcanic rock, to field-testing the permeability of sediment underlying a uranium tailings disposal facility. DBS&A has provided expertise on technical issues related to litigation and other investigations that have included characterization of the vadose zone and site hydrogeology numerical modeling of volatile organic compounds (VOCs), development of technical opinions regarding the source and distribution of contaminants attributed to numerous Potential Responsible Parties (PRPs), and expert testimony.
“Vadose Zone Hydrology” was published in 1995. Written by Daniel B. Stephens, Ph.D., P.Hg., P.G. (DBS&A founder and principal hydrologist), the book describes the elements of the physical processes most often encountered by hydrogeologists and groundwater engineers in their vadose zone projects.
Vadose Zone Hydrology Services
Vadose Zone Hydrology Applications
- Impacts of spills on groundwater
- Seepage from impoundments
- Artificial recharge
- Return flow analysis
- Alternative covers for landfills
- Cap and cover design for waste disposal sites
- Predicting contaminant migration rates
- Hydrologic budgets for water resources management
- Stream-aquifer interaction in water rights disputes
- Indoor air quality impairment investigations
- Landfill gas production