Move water by shaping ground.

What it is

EARTH-1 is the family of passive interventions that intercept storm water before it leaves the lot or the right-of-way. We treat it as a single subsystem because the components share a permit pathway, a crew skill set, and a maintenance cadence. The subcomponents are: curb cuts, infiltration basins, infiltration swales, infiltration berms, and check dams. There are sometimes also street-edge gabion structures, but Tucson's right-of-way crews have specific opinions about gabions and we mostly avoid them.

The job of EARTH-1 is to put rain where it can soak in. The Sonoran Desert receives about 11.6 inches a year on average (NWS Tucson 30-year normal), but the typical residential lot sheds 80% of that into the street within minutes of a storm because of the city's curb-and-gutter geometry and because the soil surface is usually compacted and crusted. The ground will absorb water if you give it the chance and the time. EARTH-1 gives it both: a basin spreads the water over more area and holds it in place long enough to percolate; a curb cut diverts the street's contribution onto your lot in the first place.

This subsystem is the cheapest one we run, and the most resilient. There are no moving parts. Mulch breaks down and gets topped up every two or three years. The curb cut needs occasional sediment cleared after big storms — about a wheelbarrow-full every four years on most sites. Otherwise, EARTH-1 just keeps working. The basin we dug at our first job in Sam Hughes in 2018 is still on its first set of rocks.

Schematic

Sizing rules

The basin volume rule of thumb we use comes from Brad Lancaster's drylands volume: catchment area in square feet × design rainfall in feet × runoff coefficient = required basin volume in cubic feet. We use a 1-inch design event (0.0833 ft) for residential right-of-way work in Tucson; that captures most monsoon bursts and lets the basin overflow safely on the rare 2-inch event. Runoff coefficient is 0.85 for asphalt, 0.95 for concrete, 0.50 for compacted decomposed granite, 0.30 for native gravel-mulch.

So a 600 sf section of street feeding a curb cut, with a 0.85 runoff coefficient: 600 × 0.0833 × 0.85 = 42.5 ft³, or about 5 yd³ of basin volume. We round up to 6 yd³ in practice and add 30% margin for the inevitable sediment that will reduce live volume over the life of the basin.

Bill of materials, typical 600 sf curb-cut basin

The list below is the actual page from one of our 2026 binders, lightly edited for legibility. Items priced at our wholesale, billed to the client at cost. Labor is journeyman + apprentice for one day with a Bobcat E10 mini-excavator.

Permits

Right-of-way curb cuts trigger a Tucson Department of Transportation & Mobility permit (the form lives at tucsonaz.gov/Departments/Transportation-Mobility) and, for any work touching the curb itself, a TDOT Right-of-Way Use permit. Both are inexpensive and we pull them under our R-1 license. The permit specifies a 4-inch maximum gap and requires a flow-through opening at the basin's far end so overflow returns to the gutter rather than ponding on the sidewalk. We've been doing these long enough that we know the inspector by name.

Pure on-lot earthworks (basins behind the property line, swales, berms) do not require a permit unless excavation exceeds 5 feet in depth or affects neighboring grade by more than 12 inches. We have never run a residential basin near either threshold.

Common mistakes we've watched the trade make

Three failure modes account for most of the broken EARTH-1 jobs we get called out to fix.

Basins too small. A basin sized for the average storm overflows to the street the day a real monsoon hits. We size for the 1-inch event, which is roughly the 80th-percentile Tucson monsoon storm. Anything smaller is a lawn ornament.

Curb cuts without a return. Code requires the basin's overflow to return to the gutter at a flow-through opening; in practice this is the difference between an inspector signing off on the work and citing the homeowner three years later when sediment plugs the cut. The return notch goes downstream of the cut, sized to half the cut's width.

Mulch too thin. Three inches of mulch is not enough — it crusts, doesn't hold moisture, and disappears in two summers. We lay six inches of large-chip arborist mulch on every job. It is also free, which is the part of EARTH-1 we like most.

What it pairs with

Earthworks alone won't grow a tree. The basin is a delivery mechanism; the plant is the user. We pair every EARTH-1 job with a tree from the garden — almost always a velvet mesquite or a foothill palo verde for the right-of-way, since both tolerate the heat, salt spray, and intermittent watering that a curb-cut basin produces. We will plant desert ironwood on the leeward side of the lot, where there's some wind shelter, but never in the right-of-way; it's too slow and too valuable to risk to a city work crew with a chainsaw.