Field guide · October 16, 2026
Water keeps coming back into my excavation in Sanford. What is going on?
If a Sanford excavation refills with clear water overnight after you pumped it dry, you have cut below the water table and no amount of pumping from inside the hole will keep up. Rain fills a hole once and stays gone. Groundwater comes back every night. The fix is to lower the water table from outside the cut, with a sump for shallow slow inflow or wellpoints for anything deeper or faster.
We get this call most weeks from Sanford, Lake Mary and Oviedo, usually from a GC, a pool builder or a utility crew who rented a trash pump and watched the water win. Near Lake Monroe and the St. Johns the water table can sit two to four feet below grade in the wet season, and the soil is fine sand that moves the second groundwater starts flowing through it. This guide sorts the common symptoms, says which ones are an emergency, and tells you what each fix costs off our published table.
Is it rain, or is it groundwater?
Pump it dry and look again in the morning: a dry hole was rain, a refilled hole is groundwater. Rainwater and runoff enter from the top, carry mud, and stop when the storm stops. Groundwater enters from the bottom and the lower walls, runs clear or milky with fine sand, and refills to the same level every time because that level is the water table. A third case fools people: water from one wall at one depth while the rest of the cut is dry. That is a perched layer sitting on clay or hardpan, common in the older filled lots along Seminole Boulevard and Celery Avenue, and it drains fast once a sump catches it.
| What you see | What it usually is | What fixes it |
|---|---|---|
| Hole fills after a storm, pumps dry in an hour and stays dry | Surface runoff and rain, no groundwater inflow | Rented trash pump, a berm or ditch to keep runoff out. No specialist needed. |
| Pumped dry at 5 p.m., a foot of clear water by 7 a.m. | You are below the water table. Groundwater refills the cut overnight. | Sump and open pumping for shallow slow inflow, wellpoints for deeper or fast inflow. |
| Water seeps in from one wall at a certain depth, rest of the cut is dry | Perched water on a clay or hardpan lens, common in older lakefront fill | A shallow sump at the seep, sometimes a short wellpoint line on that side only. |
| Bottom of the trench heaves, sand bubbles up, a shovel sinks in | Boiling or quick condition. Upward seepage has turned fine sand into slurry. | Stop open pumping, get people out, lower the water table from outside the cut with wellpoints. |
| Side walls slough in strips every time the pump catches up | Pumping from inside the hole pulls fines through the wall and undercuts it | Wellpoints set outside the excavation line, shoring per the trench box plan. |
| Pump runs flat out and the level never drops | Inflow exceeds pump capacity, or a limestone or shell layer feeds the sand from below | Staged wellpoints or deep wells with an engineered drawdown plan. Call before the next shift. |
Why is the bottom of my trench boiling like quicksand?
Boiling sand means groundwater is pushing up through the floor of the cut faster than the sand can hold itself together, and it is the one symptom on this page that should clear the trench right now. Engineers call it a quick condition. Upward seepage lifts the grains apart, the floor loses its bearing, and a trench box or a footing form can settle or tip. You will see small volcanoes of sand, water that runs milky instead of clear, and a floor that heaves under a boot. Pumping harder from a sump inside the hole makes it worse, because the pump steepens the pressure difference that is driving the boil. The only real fix is to drop the water table below the floor from outside the excavation, which is what a wellpoint line does.
Federal rules back this up. OSHA's excavation standard, 29 CFR 1926.651(h), bars workers from an excavation where water is accumulating unless precautions are in place, and requires a competent person to monitor any pumping equipment used to control it. A boiling floor fails that test. If a pump has already quit and the trench is filling on a live job, our emergency dewatering page covers same day response and the $750 and up mobilization charge.
Sump pump or wellpoints: which one fixes my hole?
Depth below the water table decides it. Under about three feet with slow inflow and soil that holds a wall, a sump pit in the low corner with a trash pump and a settling tank is enough, and it is the cheap option. Past three feet in the fine sand around Sanford, inflow outruns a sump, fines wash through the walls, and the cut starts sloughing. That is a wellpoint job: a row of small screened pipes jetted into the ground outside the excavation line, tied to a header and a vacuum pump, pulling the water table down before you dig. One stage reaches about fifteen feet of drawdown. Deeper cuts, or a shell or limestone layer feeding the sand from below, need a second stage or deep wells and an engineer's drawdown plan.
| Your cut | Method | Published range |
|---|---|---|
| Up to 3 ft below the water table, slow inflow, firm soil | Sump and open pumping | $1,500 to $5,000 per setup |
| 3 to 15 ft below the water table, fine sand, trench run | Single stage wellpoints | $3,000 to $8,000 per 100 ft |
| 3 to 15 ft below the water table, building pad | Single stage wellpoints around the footprint | $8,000 to $30,000 per setup |
| More than 15 ft of drawdown, or a limestone feed under the sand | Staged wellpoints or deep wells, engineered | $30,000 and up, priced from a boring log |
Pump rental with fuel and maintenance runs $1,900 to $3,300 per four weeks on top of the setup, and every setup includes a standby pump. The full table with each cost driver is on the cost guide, and the method pages explain the hardware: sump and open pumping and wellpoint dewatering.
Red flags once a dewatering crew shows up
The crew should stop a boil before they price it, and they should ask about the soil before they ask about the schedule. Watch for these:
- They answer a boiling floor by setting a bigger pump in the hole. More suction inside the cut steepens the gradient and makes the boil worse.
- Nobody asks where the water goes. Discharge in Florida runs under the FDEP dewatering generic permit, which means sediment control at the outlet and turbidity within limits. Muddy water into a storm inlet on Lake Monroe is a fine with your company name on it. See the permit guide.
- One pump, no spare. Groundwater does not pause when a diesel quits at 2 a.m., and a cut that floods overnight can take a day to recover.
- A per day price with no questions about cut depth, soil or discharge distance. That number will change at mobilization.
- Wellpoints proposed for a two foot footing cut with slow inflow. That is a $1,500 sump job dressed up as a $8,000 one.
Who should not call a dewatering contractor
Three groups are better served elsewhere. A homeowner with a flooded crawl space, garage or finished basement needs a water restoration company and a plumber, not a construction dewatering crew. A contractor with surface rainwater in a shallow cut and no groundwater inflow needs a rented trash pump for an afternoon. And a site with a full civil contractor who already owns pumps and a wellpoint trailer rarely needs a second vendor for a routine cut. Where we earn the money is sustained groundwater inflow, cuts below the water table, fine sand that boils, and any job where a missed dry date costs more than the pumping.
Send a photo of the hole
Text or send the address, how deep you are, what the water is doing, and a boring log if one exists, or call (321) 415-8927. You get the method and a range off the published table before anyone rolls, and a standby pump on every setup.