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Acid Sulfate Soils: Project Experience and L essons Learned Stafford County, VA

Acid Sulfate Soils: Project Experience and L essons Learned Stafford County, VA. Steven Hubble, Environmental Programs Manager Department of Public Works October 7, 2011. Presentation Summary. Introduction Field/Project Experience Soils Policy Recommendations Conclusion.

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Acid Sulfate Soils: Project Experience and L essons Learned Stafford County, VA

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  1. Acid Sulfate Soils:Project Experience andLessons LearnedStafford County, VA Steven Hubble, Environmental Programs Manager Department of Public Works October 7, 2011

  2. Presentation Summary • Introduction • Field/Project Experience • Soils Policy • Recommendations • Conclusion

  3. Acid Sulfate Soils • 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

  4. Acid Sulfate Soils: Not Just a Stafford County Issue

  5. Stafford County: Acid Sulfate Soil Risk Map

  6. Field/Project Experience • Small lot (1/4 acre lots) residential subdivision • Large lot (1 acre lots) residential subdivision • Transportation (Roadway-Widening) Project

  7. Small Lot Residential Subdivision • 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

  8. Before Remediation

  9. Before Remediation

  10. Before Remediation

  11. Before Remediation

  12. Before Remediation

  13. After Remediation

  14. After Remediation

  15. After Remediation

  16. Next Steps • Continue to monitor site for recurring problem areas • Mitigate remaining areas as necessary • Complete infrastructure construction and address outstanding completion items • Hold securities until issues are resolved

  17. Large Lot Residential Subdivision • Near Falmouth, VA • 63 lots (minimum of 1 acre) • Developer absent due to bankruptcy • 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

  18. Before Remediation

  19. During Remediation

  20. After Remediation

  21. Transportation Project • 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

  22. Site Conditions

  23. Site Conditions

  24. Site Conditions

  25. Soils Policy • Established by County Building Official with enabling authority from the Virginia USBC (Building Code) • 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

  26. Recommendations • 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

  27. Training Class on Acid Sulfate Soils • Training Class on this topic hosted by Virginia Association of Professional Soils Scientists • November 3 and 4-Fredericksburg, VA • http://www.vapss.org/uploads/Fredericksburg_Acid-_S_Final_Program.pdf

  28. Contact Information • Steven Hubble, Environmental Programs Manager Department of Public Works P.O. Box 339 Stafford, VA 22555 540-658-4559 shubble@co.stafford.va.us

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