Sunnyvale Excavation and Site Prep
Most Sunnyvale lots are flat, and that shapes the work. With no natural slope, rainwater goes wherever the grade sends it, and too often that’s against the house. Many of the city’s Eichler homes sit on concrete slabs with heating pipes inside them. And a lot of today’s projects are backyard ADUs that need sewer, water and power run out to a new unit.
Harris Excavation handles site prep, excavation, trenching and drainage in Sunnyvale for homeowners, general contractors and developers. We’re a licensed general engineering contractor (CSLB #1117960) based in South San Francisco, serving Santa Clara County.
Site Prep and Excavation Services in Sunnyvale
- ADU site prep: pads cut to grade and compacted to the geotechnical engineer’s spec
- Utility trenching for sewer, water and electrical lines, including PG&E service upgrades. We’re PG&E Operator Qualified. Residential trenching
- Flat-lot drainage: French drains, catch basins, dry wells and regrading. Residential drainage
- Foundation excavation for additions and new homes. Residential excavation
- Hydrovac and hand digging around live utilities and tree roots
- Commercial trenching for developers and general contractors. Commercial trenching
Backyard ADUs Start Underground
Sunnyvale’s ADU handout spells out much of the site work. A detached ADU needs at least 4 feet of side and rear setback. The city calls for a 100-amp subpanel at the ADU and 200-amp service at the main house, and tells owners to check with PG&E on upgrade availability. If the site will have more than five toilets, the building sewer has to be upgraded to a 4-inch line with cleanouts at the building and at the property line.
Each of those is a trench. We plan the sewer, water and electrical runs together, so the yard isn’t dug up more than it needs to be. Our post on what homeowners overlook when planning an ADU covers the underground costs people tend to miss.
If a new lateral connects in the street, that work needs an encroachment permit from Sunnyvale Public Works. The city asks for 10 working days to process it. Existing laterals are marked with an “S” (sewer) or “W” (water) on top of the curb.
Working Around Eichlers and Slab Homes
Sunnyvale has a number of Eichler neighborhoods. Many Eichlers heat through radiant pipes buried in the concrete slab, and repairing one means breaking out concrete. Before we trench along a foundation or cut near the slab, we ask what’s in it and where it runs. Outside the house, we keep the dig from undermining the slab edge.
Drainage is the other half. A geotechnical study for a downtown Sunnyvale project describes the ground as alluvial clays and sands with low to moderate expansion potential. Clay that stays wet keeps moisture under a slab long after a storm. On a flat lot, the fix is usually a modest regrade that pitches water away from the house, plus a French drain or catch basins that carry it somewhere useful.
Sunnyvale’s Dripline Rule
Sunnyvale protects trees 38 inches or more in circumference measured 4.5 feet above the ground, or multi-trunk trees whose trunks add up to 113 inches. The city’s code counts trenching, excavating, changing the grade or paving inside a tree’s dripline as damage. During construction, protected trees get fencing at least 4 feet high at the dripline, and the existing grade stays put out to the dripline unless the city approves otherwise. Fines for substantially damaging a protected tree run $5,000 to $25,000 per tree.
When a utility line has to cross a dripline, we work out the route with your arborist and dig by hand or by hydrovac where roots are close.
Nearby Project: Hydrovac Trenching in Cupertino
Next door in Cupertino, we excavated a trench for a new electrical service in a congested alignment, with existing electrical, gas and telecommunications lines already in the way. We brought in a hydrovac truck, which works like a pressure washer paired with an oversized shop vac, so the crew could excavate around live utilities without damaging them. Read about the Cupertino job.
Where We Work in Sunnyvale
We work across Sunnyvale, including Cherry Chase, Birdland, Ponderosa Park, Lakewood Village, Washington Park and the Heritage District. Nearby, we also serve Santa Clara, San Jose, Palo Alto, Cupertino, Mountain View and Los Altos. See all our Santa Clara County service areas.
Sunnyvale Excavation FAQ
What underground work does a backyard ADU need?
Usually trenches for sewer, water and electrical out to the new unit, and sometimes an electrical service upgrade and a larger sewer line.
Can you dig next to my Eichler?
Yes. Tell us if the house has radiant heat in the slab. We plan the trench route around it and hand dig close to the foundation.
Can you trench near a protected tree?
Yes, with care. Sunnyvale counts trenching inside a protected tree’s dripline as damage, so we route the line with your arborist and dig by hand or hydrovac where needed.
Do you work directly with homeowners?
Yes. We work directly for homeowners and as the excavation subcontractor for general contractors and developers.
Get a Sunnyvale Site Prep Estimate
Send us your ADU or site plans and any soils or arborist report. We’ll walk the lot, map out the trenches and grading, and send a clear written estimate. Request a free estimate