Exploratory Test Pits in Savannah Georgia: Subsurface Verification for Coastal Plain Conditions

Q: What does an exploratory test pit cost in Savannah?

For a standard test pit in the Savannah area, budget between US$550 and US$810 per pit. The range accounts for mobilization distances within Chatham County, the depth specified (typically 8 to 14 feet), and whether groundwater pumping is required during logging. A multi-pit program on a single site reduces the per-unit cost because the backhoe and field crew are already on location.

Q: How deep can a test pit go in Savannah before the water table becomes a problem?

In central Savannah, the surficial water table is encountered between 4 and 7 feet below grade. Below that depth, the pit requires continuous dewatering with a trash pump. We can log to approximately 14 feet with a standard backhoe, but the face must be benched or sloped per OSHA excavation safety requirements once the depth exceeds 5 feet.

Q: Do I still need drill rig borings if I have test pits?

Test pits and drill borings serve complementary roles. A pit gives you a continuous visual profile and lets you identify thin seams, fill layers, and the exact water table depth. A boring with SPT provides blow count data at greater depth and allows laboratory testing of undisturbed samples. On most commercial projects in Savannah, we recommend at least one test pit combined with a boring program to satisfy both IBC visual classification and the deeper bearing capacity evaluation.

Between the dense sands of the Victorian District and the soft marsh-edge clays near Thunderbolt, the ground beneath Savannah shifts dramatically within just a few blocks. After opening dozens of pits across Chatham County, our team has seen firsthand how the Pleistocene terrace deposits and recent alluvial fills create two entirely different excavation behaviors less than a mile apart. An exploratory test pit lets you see the stratigraphy directly, measure the seasonal water table at roughly 4 to 7 feet below grade, and decide on foundation depths before the backhoe even leaves the site. When the IBC requires a bearing stratum verified by visual inspection, this method delivers answers that a drill rig alone cannot, especially where the SPT drilling data needs ground-truthing against what the eye can confirm.

Opening a test pit in the Coastal Plain means confronting the water table directly — if you cannot control it, you cannot log it accurately.

Process and scope

Savannah sits on the lower Atlantic Coastal Plain, where the Hawthorne Group sediments are capped by Pleistocene sands and silts that rarely exceed 30 feet in thickness before hitting the confining Marl layer. At a typical test pit depth of 10 to 14 feet, we encounter the Surficial Aquifer perched on that low-permeability Marl, which means water inflow begins gradually and must be managed with a trash pump during logging. Our field geologists classify materials per ASTM D2487, capturing the transition from medium-dense SP-SM sands to the fat clays that dominate the eastern side of town. A pit near DeRenne Avenue might reveal clean sand to full depth, while one along the Vernon River corridor hits organic silt by the fifth foot. We log each lift with Munsell color, moisture condition, and pocket penetrometer readings, giving the structural engineer a continuous profile that no split-spoon sample interval can replicate. In Savannah's climate, where summer humidity hits 90 percent and thunderstorms roll in by early afternoon, test pits are typically scheduled for morning excavation with immediate backfill to keep the walls stable and the site safe.

Exploratory Test Pits in Savannah Georgia: Subsurface Verification for Coastal Plain Conditions

Local ground factors

A visual-only assessment from drill cuttings proves inadequate for the soil classification mandated by IBC Section 1803 in Savannah's low-lying properties, especially those within the FEMA AE flood zone covering much of the city south of Bay Street. An excavated pit provides an uninterrupted exposure where narrow layers of decayed vegetation, former topsoil, or historical wetland sediments become readily apparent. In the Starland District, we have encountered unrecorded fill strata containing fragments of brick and oyster shell only three feet beneath the surface—material that would be missed in a conventional SPT sampler. Overlooking such lenses can lead to reports of uneven settling within the initial two years of occupancy. Moreover, for properties situated in the 100-year flood zone, the pit also records the peak seasonal water table, which directly impacts foundation design and the requirement for sub-slab drainage as stipulated by ASCE 7 flood provisions.

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Reference standards

Geotechnical investigations must adhere to IBC Section 1803, while soil classification follows ASTM D2487 and ASTM D2488, and site classification is per ASCE 7-22 Chapter 20.

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Standard Exploratory Pit

For single-family residential lots in the Ardsley Park and Parkside neighborhoods, where bearing sands are anticipated, a single pit excavated to a maximum depth of 12 feet is employed. The pit includes a stratigraphic log in accordance with ASTM D2488, Munsell color notation, moisture condition evaluation, and photographic documentation of all exposed faces.

Instrumented Test Pit Program

For commercial developments that need IBC special inspection documentation, a grid pattern of multiple pits is utilized. These pits undergo in-situ density testing using a drive ring, pocket penetrometer, and torvane readings for each lift, along with groundwater monitoring spanning a 48-hour recovery period.

Forensic Exposure and Fill Verification

Pits are strategically placed to reveal existing footings, confirm the thickness of unrecorded fill, or examine signs of distress. The process encompasses sampling for laboratory classification and a written assessment of fill suitability in accordance with Chatham County's grading requirements.

Typical parameters

Parameter	Typical value
Maximum practical depth (standard backhoe)	14 ft
Typical water table depth in central Savannah	4–7 ft below grade
Soil classification standard	ASTM D2487 (Unified Soil Classification System)
In-situ testing per lift	Pocket penetrometer, torvane, density drive ring
Dominant surficial geology	Pleistocene sand and silt over Hawthorne Group Marl
Average log interval per pit	Every 18–24 inches or at stratum change
Typical pit dimensions (L x W)	8 ft x 4 ft (adjustable per access)

Frequently asked questions

What does an exploratory test pit cost in Savannah?

In the Savannah region, anticipate a cost ranging from US$550 to US$810 for a standard test pit. This variation reflects mobilization distances across Chatham County, the chosen depth (usually between 8 and 14 feet), and the need for groundwater pumping during logging. When multiple pits are scheduled on a single site, the per-pit expense decreases since the backhoe and field team are already present.

How deep can a test pit go in Savannah before the water table becomes a problem?

The surficial water table in central Savannah lies at depths ranging from 4 to 7 feet beneath the surface. Excavations below this level necessitate ongoing dewatering using a trash pump. A typical backhoe allows logging to around 14 feet, but once the excavation depth surpasses 5 feet, OSHA safety regulations require benching or sloping of the face.

Do I still need drill rig borings if I have test pits?

Drill borings and test pits play complementary functions. An excavated pit offers an uninterrupted visual section, enabling identification of narrow strata, fill deposits, and the precise water table level. Conversely, SPT borings deliver blow count information at deeper elevations and permit laboratory examination of undisturbed specimens. For the majority of commercial developments in Savannah, we advise incorporating at least one test pit alongside a boring program to meet both IBC visual classification requirements and the need for deeper bearing capacity assessment.

How quickly can a test pit be scheduled and backfilled in Savannah?

Most residential test pits are excavated, logged, photographed, and backfilled within a single morning, typically 3 to 4 hours on site. We schedule early starts to beat the afternoon thunderstorms common in the Coastal Plain from May through September. Backfill is compacted in lifts with the excavator bucket, and the surface is restored to grade. A written log with photos is delivered within 48 hours. More info.