Pull precise site elevation to evaluate slope and gravity-flow feasibility before designing a septic system

domain: epqs.nationalmap.gov · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗

Steps

  1. Call https://epqs.nationalmap.gov/v1/json?x={lon}&y={lat}&units=Feet&wkid=4326&includeDate=false for a single elevation reading at the proposed tank/drainfield location.
  2. Repeat the call at multiple points across the parcel (tank location, distribution box, drainfield corners) to compute rise/run and estimate slope percentage.
  3. Compare the calculated slope percentage against your state's septic design slope thresholds (many require gravity systems only under roughly 15% slope).
  4. For sites near the threshold, cross-check against the NRCS SSURGO slope class attribute (via Soil Data Access) as an independent estimate.
  5. Cache the raw elevation values with the query coordinates in your design file for the permit submission.

Known gotchas

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