ADA Ramp Surveys in Mill Valley, CA

Mill Valley has adopted an ADA transition plan, and the hardest part of carrying one out here is the terrain. The town runs up the canyons on the flank of Mount Tamalpais, so a sidewalk in Mill Valley is often descending a real grade while it is also trying to hold a cross slope under 2 percent, and the two constraints fight each other. Downtown around Lytton Square and the Throckmorton and Miller corridors, the walks are old, heavily used, and lifted in places by redwood and street-tree roots, which turns a nominally flat block into a series of short humps with abrupt changes in level. Add public stairways, driveway aprons cut into a grade, and building entries that sit a step or two above a sloping walk, and the accessible route becomes a sequence of small measurements rather than one long one.

That sequence is exactly what handheld readings get wrong. A ramp run is limited to 8.33 percent, cross slope to 2.083 percent under the 2010 ADA Standards and 2 percent under California Building Code Chapter 11B, landings to a 60-inch minimum length, and curb ramp flares to 1:10. A two-foot level bridges over a root heave and reports a slope that no wheel ever experiences. Our terrestrial laser scanner records the whole walk, the ramp faces, the gutter line, and the adjacent street as one continuous surface, and we compute running slope and cross slope from it at any interval, across full width. Steep, narrow streets are also safer to scan than to walk with a rod, which matters on the hillside blocks.

You get slope and cross-slope plans with spot elevations, change-in-level callouts at thresholds and joints, ramp tables, and a DWG base map for the designer. We measure; the CASp or architect certifies. See ADA compliance surveys and topographic surveys in Mill Valley.