Acid Sulfate Soil (Hubble) - Potomac Watershed Roundtable

Steven Hubble, Environmental Programs Manager
Department of Public Works
October 7, 2011
 Introduction
 Field/Project Experience
 Soils Policy
 Recommendations
 Conclusion
 Naturally occurring soils or sediments formed under
waterlogged conditions
 Contain iron sulfite materials (pyrite)
 Are benign while underground
 Become acidic when excavated and left exposed on the
surface to oxygen
 Small lot (1/4 acre lots) residential subdivision
 Large lot (1 acre lots) residential subdivision
 Transportation (Roadway-Widening) Project
Located near Falmouth, VA
147 lot cluster residential lot subdivision
Avg. lot size 8,000-10,000 sq. feet (sod required for lots)
1 developer (local), 2 builders (1 regional, 1 national)
Construction begins late 2005/early 2006
Acid Sulfate and Soil Stabilization problems noted in 2009
VT staff (Lee Daniels) contacted for assistance
Soil testing conducted and remediation plans developed by
developer and builders through geotechnical/engineering
consulting firm
 Significant remediation activities completed in 2009/2010
 Remediation activities continue/complete
 Soil pH readings range from normal to +/- 2.5 pH
 Continue to monitor site
for recurring problem
 Mitigate remaining areas
as necessary
 Complete infrastructure
construction and address
outstanding completion
 Hold securities until
issues are resolved
 Near Falmouth, VA
 63 lots (minimum of 1 acre)
 Developer absent due to
 County utilizing security
funds to complete
infrastructure improvements
 Acid Soils encountered
during completion of
neighborhood stormwater
management pond
 Acid soils relocated to other
parts of the neighborhood
 Widening of a roadway
from 2 to 4 lanes
 Road improvements
proffered and constructed
by a developer for VDOT
 Acid Soils prevalent in the
area (Quantico Slate) and
unearthed during initial
road construction (late
80’s/early 90’s)
 Large underground
electrical transmission line
is located in the area
 Established by County
Building Official with
enabling authority from the
Virginia USBC (Building
 Soil evaluation required for
acid sulfate soils and other
soil issues (shrink swell,
compacted fill)
 If acid soils are suspected,
testing is required
 If the test does not register
between pH of 5.5 and 7.5,
then mitigation to improve
soil pH is required
 Use Statewide soils data merged with locality specific
data to identify potential risk locations
Attempt to identify problem soils prior to excavation
If acid soils excavated during cut, place those soils in a
deep fill area where they will not be exposed to oxygen
Educate inspectors/staff on acid soils to help them
identify in the field if exposed
Consider regulations that address acid soils at the
development plan or building permit stage
Ask for help if you encounter acid soil problems
 Training Class on this topic hosted by Virginia
Association of Professional Soils Scientists
 November 3 and 4-Fredericksburg, VA
 Steven Hubble, Environmental Programs Manager
Department of Public Works
P.O. Box 339
Stafford, VA 22555
[email protected]