Inventory and Data Collection
This domain tests how you choose, read, and trust base information before drawing a line. Expect questions on survey types, public map sources, scale, datum, and the limits of each data set.
Survey types
- Boundary survey: property lines, easements, rights-of-way, encroachments. It is not a topographic survey.
- Topographic survey: contours, spot elevations, utilities, trees, benchmarks. Design surveys commonly use 1- or 2-ft contours.
- ALTA/NSPS Land Title Survey: due-diligence survey tied to title; confirms easements and improvements.
- Geotechnical report: borings, groundwater, bearing capacity-never inferred from a soil map.
Public sources
- USGS 7.5-minute quadrangles: 1:24,000, usually 10- or 20-ft contours; regional context only.
- NRCS Web Soil Survey: soil series, drainage class, hydric soils; not a substitute for wetland delineation.
- FEMA FIRM: 1% annual-chance floodplain and floodway; the floodway is the regulated conveyance area where fill is restricted.
- NWI maps and the USACE 1987 Manual: wetland screening and jurisdictional delineation.
Worked example
A site drops from 124 ft to 96 ft over 280 ft. Slope = (124 − 96) ÷ 280 × 100 = 10%. At 10%, a standard accessible route is not feasible without a ramp or retaining walls. If the same drop occurred over 560 ft, slope would be 5%-exactly the 1:20 running-slope limit for an accessible route, so cross slope must still be held to 1:48 or flatter.
Traps
- Using a quadrangle to set finished grades.
- Calling NWI mapping a jurisdictional wetland line.
- Mixing NAVD 88 and local datum.
- Confusing the floodway with the full 100-year floodplain.