Site Assessment and Grading
What the exam tests
Site Assessment and Grading tests whether you can read a site before design: survey, contours, spot elevations, soils, drainage patterns, utilities, access, and permit triggers. Grading questions often hinge on slope math, drainage direction, and cut/fill balance.
Core rules
- Inventory before drawing: property lines, easements, setbacks, utilities (call 811 before digging), existing trees, wells, septic, flood zone, shoreline, and erosion controls.
- Read contours: closely spaced contours mean steep slope; contours pointing uphill form a swale; pointing downhill form a ridge.
- Calculate slope as rise ÷ run × 100. Keep positive drainage away from structures, typically 2% minimum on soil and 1–2% on paving.
- Balance cut and fill where possible; stockpile topsoil separately and protect it from erosion.
- Use best management practices: silt fence, inlet protection, stabilized construction entrances, and dust control. Disturbance thresholds can trigger a stormwater permit and SWPPP.
Worked example
Two spot elevations are 100.0 ft and 98.5 ft, 30 ft apart. Rise = 1.5 ft; run = 30 ft; slope = 1.5 ÷ 30 × 100 = 5%. Reasoning: the ground falls 5 ft per 100 ft, which is too steep for a lawn area but acceptable for a swale or planted slope. If the high point is next to a building, verify that the building pad drains away at 2% minimum and that the swale has a stable outlet. A 5% slope also needs erosion control until plants establish.
Traps
- Reversing rise and run or forgetting to multiply by 100.
- Grading toward the house because the finished floor 'looks high enough.'
- Ignoring existing drainage patterns and creating a pond.
- Stockpiling soil in a swale or against a tree.
- Assuming a utility is deep enough without locating it.
- Starting grading before checking permits, tree ordinances, or shoreline rules.