Amended Soils for Stormwater Treatment


Projects using amended soils in Low Impact Design (LID) storm drainage facilities have become more prominent in recent years.  As with many design elements that have a relatively short history of use, rain gardens and bio-retention facilities using amended soils for treatment of stormwater runoff present challenges to many consultants, regulatory agencies and testing companies.  Some of these challenges are due to changes in the governing municipalities design manual, limited or vague performance criteria, or a lack of empirical data.  GeoTest’s team of Engineers, Geologists and Special Inspectors can help with these challenges.  We have recently participated with several other leading Western Washington consulting firms and the WSU Puyallup Research and Extension Center in a City of Seattle funded study to develop test methods designed to establish performance and testing criteria for amended soils.

Testing and Inspection services typically associated with Amended Soils include:

  • Subgrade Verification
  • Soil Characterization by Sieve Analysis
  • USDA soil textural analysis
  • Permeability Test (ability of amended soils to infiltrate water)
  • Moisture/Density Relationships (Proctor)
  • Organic Content
  • Moisture Testing
  • In-Place Density of Amended Soil (Compaction Testing)
  • Observation of Installation Methods
  • Cation Exchange Capacity

GeoTest is available to provide consulting services that include sizing, placement, drawings, and cost estimates.  Our diversity of skills allows us to provide a comprehensive approach as a geotechnical consultant and a quality assurance/control specialist.

Give us a call to see how our professionals can assist with your stormwater treatment design needs.  Call us at 888-251-5276, email us at or visit us online at

– The GeoTest Team