17.3 Documenting Site Features: Survey, Civil, Grading, Utilities & Landscape

PDD objective 2.2 asks you to determine appropriate documentation of site features. Site documentation is produced by several disciplines at once, and the recurring failure is a gap or a contradiction between the architectural site plan and the civil drawings.

Who Documents What

The boundary between the architectural site plan and the civil drawings must be stated explicitly in the documents. A common convention is that civil documents the site up to approximately 5 feet from the building and architecture documents everything inside that line, but the convention varies by firm and by project, and an unstated boundary is how a stoop, an area drain, or a bollard ends up in neither contract.

The Survey Is the Basis of Everything

Every site drawing is built on the survey, and the survey establishes:

• Boundary and bearings, with recorded easements and rights-of-way.
• Existing topography, usually at 1-foot or 2-foot contour intervals.
• A benchmark and a vertical datum. Every spot elevation in the set must reference the same datum. Mixing an assumed site datum with a published geodetic datum produces a building set at the wrong elevation, and it is discovered during excavation.
• Existing utilities, their size, material, and invert elevations.
• Existing improvements, trees, and encroachments.

Under AIA B101 Article 5 the owner furnishes the survey and the geotechnical report. The architect verifies that what was furnished actually covers the design.

Grading and Drainage Documentation

Grading is documented with contours for general form and spot elevations for control points. Spot elevations govern wherever precision matters:

• Finish floor elevation, and the elevation at each door threshold
• Top of curb and gutter flow line
• Top and bottom of walls and stairs
• High points, low points, and the rim and invert of every drainage structure
• Every point along an accessible route where slope must be verified

Two rules do most of the work. First, positive drainage away from the building: the ground should fall away from the structure for a minimum distance, and a paved surface generally needs at least a 1% slope to drain (2% for most grass areas). Second, accessible route slopes are documented, not assumed: an accessible route may not exceed 1:20 running slope without becoming a ramp, and cross slope may not exceed 1:48, so the drawings must carry enough spot elevations to prove compliance.

Utilities, Erosion Control & Site Details

• Utility plans show routing, size, material, invert elevations, and the point of connection to each service, along with required separations between water and sewer.
• Erosion and sediment control plans document silt fence, inlet protection, construction entrances, and stabilization measures required by the project's stormwater permit, and they are typically a prerequisite to any land disturbance.
• Stormwater management documents detention or retention volume, outlet control structures, and any low-impact development measures such as bioretention or permeable paving.
• Site details resolve paving sections, curbs, walls, fences, bollards, tree protection, and trench sections — the pieces that appear on every project and are most often copied forward without checking.

Coordinating the Site Documents

Exam Tip: When an item describes a conflict between drawings, ask which discipline owns the information. The survey owns existing conditions and datum, civil owns grading and site utilities, landscape owns planting and irrigation, and architecture owns the building and the accessible route from the property line to the entrance. The correct response is to resolve the conflict at the owning discipline, not to redraw it on the architectural sheet.