Screen a parcel for hydric soils and shallow seasonal water table using NRCS Soil Data Access before designing a French drain / foundation drainage system
domain: sdmdataaccess.nrcs.usda.gov · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
POST a SQL query to https://SDMDataAccess.sc.egov.usda.gov/Tabular/post.rest joining mapunit to the muaggatt table for the map unit(s) intersecting the parcel
Pull wtdepannmin (annual minimum water table depth, cm) and drclassdcd (dominant drainage class) from muaggatt to gauge how close to the surface groundwater typically rises
Pull hydclprs (hydric classification presence — an area-weighted class describing how much of the map unit is hydric) from muaggatt to flag hydric-influenced map units
For component-level detail, join to the component table's hydricrating field (Yes/No/Unranked) rather than relying solely on the map-unit aggregate
Use a shallow wtdepannmin combined with a 'somewhat poorly drained' or wetter drclassdcd as the trigger to size a footing/perimeter drain for higher seasonal water tables
Known gotchas
hydclprs and drclassdcd are map-unit aggregates weighted across components — a parcel can straddle multiple components with very different drainage; don't assume homogeneity
SSURGO water table depth is a modeled/typical seasonal value from soil survey observations, not a real-time or site-specific groundwater measurement — use USGS field-measurements data or a site boring for actual current conditions
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