Highly Erodible Soil
Soil erosion can increase and create problems for the construction of homes, roads and utilities. Gullies created by eroding soils can undercut slopes and cause instability. Erosion wastes valuable topsoil and causes water pollution by carrying nutrients like phosphorus and nitrogen into streams and lakes. Many of these pollutants can also reach ground water.
Soil erodibility is based upon factors such as soil texture, slope length and slope steepness. Highly erodible soil is less resistant to the erosive action of rain and flowing water. However, soil that may be more resistant to erosion can also contain silt and clay that once eroded and suspended in runoff can be very difficult to remove from storm water even when using sediment control measures. Small suspended soil particles can cause extensive water pollution problems.
(Photo Left) Deep gully in highly erodible soil at construction site south of Morrison.
(Photo right) Common sediment control measures, like straw bales, do not work on steep sites with highly erodible soil. This photo is from a roadside swale in a residential development south of Morrison.
Sensitive Soil
Soil formation is a very slow process. Soils cannot renew their eroded surface while erosion continues to degrade the soil and any erosion can greatly reduces soil productivity. It can take hundreds of years for the renewal of eroded soil, given the topography and climate of the Jefferson County.
Jefferson County contains sensitive soils that are very thin with limited rooting depths and organic matter and steep slopes that are prone to erosion. Revegetation attempts on steep, thin soils with little organic matter often fail and can result in long-term erosion and non point source pollution. The key factors that determine how sensitive a soil is to disturbance include: depth to bedrock, organic matter and permeability.
Click here for sensitive soil map
Expansive Soils
Jefferson County contains soils that can shrink when dry and swell or expand when wet. Shrinking and swelling can damage roads, building foundations and other structures. Expansive soil and bedrock is widespread along the Front Range. Historically, Jefferson County has had the highest damage losses from expansive soils in the nation.
(Photo Right) Basement walls and floor severely damaged from expansive soils. Metal jacks used to brace walls bent by pressure from expanding soil.
(Photo Above) Expansive soils caused severe heaving of sidewalk. Though the house looks fine from the outside; it was structurally damaged.
Click here for expansive soil map
