Soil Map Unit Description from the RI Soil Survey Report (2010 Update)
WBn0: Billington silt loam, 0 to 1 meter water depth (2010 Update for the RI Coastal Zone Soil Survey
Phase I - please download the latest copy of the spatial data).
This subaqueous soil is found in low energy mainland coves in coastal bays and
lagoons. Mapped areas are irregular in shape and range in size from 0.5 to 8
hectares (1 to 20 acres). Slope ranges from 0 to 3 percent.
Typically, this soil has a fluid, black surface layer, 40 to 90 cm thick,
derived from marine and\or estuarine silts. The substratum is very dark brown
organic muck derived from Atlantic white cedar (Chamaecyparis thyoides)
swamp or Spartina sp. marsh deposits, 40 to 100 cm thick.
Billington soils are permanently submerged beneath up to 1 meter of salt or
brackish water. All horizons have a neutral pH in place and a highly acidic pH
Sulfidic materials occur within 50 cm of the soil surface, and typically the
entire mineral portion of the soil contains highly sulfidic materials that if
drained or dredged and exposed to air, will oxidize and create acid sulfate
Included with this soil in mapping are areas of Pishagqua silt loam soils in low
energy lagoon bottom landscapes where organic horizons are not encountered.
Anguilla soils may be included on submerged mainland beaches. Napatree soils may
also be found in the mapping unit on submerged mainland beaches. Also included
in mapping are small areas of Fort Neck silt loam which do not have an organic
horizon within 100cm of the soil surface. Included areas make up about 15
percent of the map unit.
Billington soils provide important eelgrass (Zostera marina) habitat as
well as habitat for fish and shellfish. Benthic fauna such as tubeworms, clams,
juvenile blue crabs, scallops, and juvenile finfish are associated with this