GNG Underground LLC

Concrete flatwork covers everything flat and horizontal: garage and shop slabs, patios, sidewalks, equipment pads and aprons. Most of what determines whether a slab lasts happens before the truck arrives. The subgrade is compacted, a gravel base of about four inches is placed and compacted, forms are set to grade with slope away from the building, and reinforcement, typically wire mesh or #3 or #4 rebar on chairs, is placed. Residential slabs are usually four inches thick and poured at 3,000 to 4,000 psi; anything that will see trucks or equipment goes to five or six inches. Control joints are cut at intervals of roughly two to three times the slab thickness in feet, so about every eight to twelve feet on a four-inch slab, because concrete will crack somewhere and joints tell it where. Concrete needs about seven days before foot traffic and twenty-eight to reach design strength.

Decorative concrete is standard flatwork with a finish applied while it is wet or after it cures: stamped patterns that mimic stone, slate or wood plank, integral or broadcast color, acid or water-based stains, exposed aggregate, and polymer overlays that resurface an existing slab. The finish adds a lot of labor in a short window. On a stamped pour the crew has to place, color, stamp and detail the whole slab before it sets, so crew size and weather matter more than on plain concrete. Because the surface is the product, the base, thickness, reinforcement and joint layout still have to be right, and joints should be planned into the pattern rather than cut across it afterward. Sealer is what keeps color and finish looking new; most decorative surfaces need resealing every two to three years, and stamped surfaces can be slippery when wet unless a grit additive is used.

Driveway contractors build the surface between the road and the house, from a gravel farm lane to a poured concrete approach, and the base under the surface decides how long any of them last. A typical driveway is excavated to remove topsoil, graded with a crown or cross slope so water runs off, and built up with four to eight inches of compacted crushed stone before the top layer goes on. Where the driveway crosses a roadside ditch it needs a culvert sized by the county, and the connection to a public road is regulated by the road authority. Gravel is the least expensive and needs regrading every year or two; asphalt costs more and needs sealing; concrete costs the most up front and lasts longest if the base and joints are done right.

Erosion and sediment control keeps disturbed soil on the site and out of storm drains, ditches and neighboring property while construction is under way and until vegetation is established. Under the federal Clean Water Act, any project that disturbs one acre or more needs coverage under a construction stormwater permit and a written plan, commonly called a SWPPP, and many cities set lower thresholds. The physical work is simple and unglamorous: silt fence trenched in along the downhill perimeter, a stone construction entrance so trucks do not track mud onto the road, protection around every inlet, check dams in ditches, and erosion control blanket or hydroseed on slopes. What most owners underestimate is the maintenance: controls have to be inspected after every rain of a quarter inch or more and repaired, and inspectors write violations for torn fence and full silt traps, not for missing paperwork.

Excavation contractors dig and move earth for foundations, basements, utilities, pools and site cuts. Most residential jobs run on a mini or mid-size excavator paired with a skid steer and a dump truck; larger cuts bring in a dozer or scraper. The price depends less on the size of the hole than on what is in the ground: clay, ledge rock, high groundwater and buried utilities all slow the machine down and change the hauling math. Before the bucket touches dirt the site needs an 811 utility locate, and any trench deeper than five feet needs a protective system under OSHA rules.

Grading is the shaping of ground to a designed elevation and slope. Rough grading moves the bulk of the earth to bring a site close to plan; finish grading dials in the last few inches so a pad is level and a yard sheds water. The number that matters is fall: building codes call for the ground to drop at least six inches in the first ten feet away from a foundation, and a lawn or gravel area needs roughly a two percent slope to drain. Crews do this with a dozer, a skid steer with a grading bar, or a motor grader on larger lots, checked against a laser or GPS grade stake rather than by eye.

Pond and water management contractors excavate and shape ponds, build or repair the embankment dams that hold them, and cut the ditches, swales and channels that move water across a property. A pond that holds water starts with the soil: it needs a clay core or a compacted clay liner, or a synthetic liner where the ground is sandy or rocky, and the dam is built in compacted lifts with a keyway cut into the original ground. Every pond also needs a way to pass the big storm, usually a principal spillway pipe plus an emergency spillway cut in natural ground, sized for the watershed above it. USDA NRCS publishes free design standards for farm ponds that most contractors follow. Cleanouts, which remove years of silt and reshape banks, are common on older ponds and are priced by the cubic yard removed and where that muck can be spread.

Retaining walls hold back soil where a grade change is too steep to slope, and they fail for one reason far more than any other: water. A wall that lasts has a compacted crushed-stone base, a perforated drain pipe at the heel, clean gravel backfill behind the wall face, and geogrid layers tied into the backfill on anything tall. Segmental concrete block is the most common residential system and can be built by a landscape contractor up to about four feet; above that, or wherever a driveway, slope or structure sits above the wall, an engineer's design is required by most codes and the wall becomes structural work. Poured concrete and reinforced masonry walls are used for tall cuts and tight sites, boulder walls for rural and natural-look projects, and pressure-treated timber for budget walls with a shorter life.