Whether you are building a detached garage, adding outdoor lighting to your property, or running power to a workshop or well pump, there is a good chance the wiring needs to go underground. Underground electrical wiring is one of those projects that looks straightforward on the surface but involves strict code requirements, specific materials, and real consequences if done wrong. In Aiken, SC, the combination of clay-heavy soils, high water tables in some areas, and active root systems from mature trees makes underground wiring something you want done right the first time.
Here is what every Aiken property owner should understand before any wire goes into the ground.
UF Cable vs. Conduit: Understanding Your Options
There are two primary methods for running electrical wiring underground, and each has distinct advantages depending on your situation.
UF (Underground Feeder) cable is a special type of electrical cable designed for direct burial in the ground without any protective covering. The conductors are encased in a solid, waterproof plastic jacket that resists moisture, fungus, and corrosion. UF cable is the simpler option for many residential runs because it eliminates the need for conduit along the buried portion. However, it must still be run through conduit where it transitions from underground to above ground, such as where it enters a building or rises up a post.
Conduit systems use PVC (Schedule 40 or Schedule 80), rigid metal conduit (RMC), or intermediate metal conduit (IMC) as a protective pipe, with individual THWN or XHHW conductors pulled through the pipe. Conduit offers superior physical protection for the wiring and allows for easier future upgrades. If you ever need to pull new or larger wire, you simply pull it through the existing conduit instead of digging up the yard again. For larger installations, feeders to subpanels, or commercial applications, conduit is typically the better long-term investment.
The method you choose directly affects the required trench depth, which is the most important code issue in underground wiring.
Trench Depth Requirements: What the Code Says
The National Electrical Code (NEC) specifies minimum burial depths based on the wiring method and the voltage involved. For standard residential 120/240-volt circuits, here are the key requirements:
Direct-buried UF cable: Minimum 24 inches deep. This is the deepest requirement because the cable has no external physical protection beyond its own jacket. If the circuit is protected by a ground-fault circuit interrupter (GFCI), the minimum depth can be reduced to 12 inches for 120-volt circuits only, but most electricians still recommend the full 24 inches for long-term protection.
Rigid metal conduit (RMC) or intermediate metal conduit (IMC): Minimum 6 inches deep. Metal conduit provides the best physical protection, which is why the code allows a shallower trench. This is useful when you are running wire under existing concrete slabs, driveways, or areas where deep trenching is impractical.
PVC conduit (Schedule 40): Minimum 18 inches deep. PVC provides good protection but is not as impact-resistant as metal, so it requires a deeper trench than RMC or IMC.
These are minimums. In Aiken, where heavy equipment like riding mowers, tractors, and fence post drivers are commonly used on residential properties, going deeper than the minimum is smart insurance against accidental damage.
Frost Line and Soil Conditions in Aiken
Frost line depth matters for underground wiring because frozen ground can shift and stress buried cables or conduit. The good news for Aiken property owners is that South Carolina has one of the shallowest frost lines in the country. In the Aiken area, the frost line is approximately 6 to 8 inches, which means the standard NEC burial depths already place your wiring well below the freeze zone.
Soil conditions are a bigger practical concern in this area. Much of Aiken County has sandy loam or clay soils, and some areas near creeks and low-lying land have high water tables. Clay soil is particularly challenging because it retains water and expands when wet, which can put pressure on buried conduit over time. Sandy soil drains well but can shift, and tree roots from the area's abundant pine and oak trees can work their way into conduit joints if they are not properly sealed.
A professional installation accounts for these local soil conditions with proper bedding material (usually sand or fine gravel around the cable or conduit), sealed conduit joints, and appropriate routing that avoids known drainage paths and root zones where possible.
Call Before You Dig: It Is the Law
Before any shovel, trencher, or backhoe breaks ground in South Carolina, you are legally required to call 811 or submit a request through South Carolina 811 (sc811.com) at least three full business days before digging. This is not optional and it is not just a good idea. It is state law, and violating it can result in fines and personal liability for any damage.
When you call 811, utility companies send locators to your property to mark the approximate locations of all underground utilities: gas lines, water lines, sewer lines, telecommunications cables, and existing electrical lines. The markings are color-coded. Red marks indicate electrical. Yellow marks indicate gas. Blue marks indicate water. Orange marks indicate telecommunications.
In rural areas around Aiken, where properties may have well water lines, septic systems, propane lines, and underground electrical feeds from decades ago, knowing what is already in the ground is critical. Hitting a gas line or an existing high-voltage feed with a trencher is not just expensive. It is life-threatening.
What Underground Wiring Costs in Aiken
Underground electrical wiring costs vary significantly based on the distance, the wiring method, soil conditions, and what you are powering at the other end. Here are typical ranges for the Aiken area:
Short runs (under 50 feet) for lighting circuits or small outbuildings: $500 to $1,500 including trenching, materials, and labor. This covers a basic 20-amp circuit run in UF cable or PVC conduit to a detached shed, post light, or landscape lighting transformer.
Medium runs (50 to 150 feet) for workshops, garages, or pool equipment: $1,500 to $4,000. These typically require larger wire sizes to handle voltage drop over the longer distance, and often involve a subpanel at the destination to distribute power to multiple circuits.
Long runs (150+ feet) for barns, detached living spaces, or well pumps: $3,000 to $8,000+. Long runs require careful voltage drop calculations, larger conductors, and often 240-volt feeds. The trenching alone on a 300-foot run through clay soil can be a significant portion of the cost.
Trenching by machine (a walk-behind trencher or mini excavator) is far more cost-effective than hand digging. However, some areas near existing utilities, foundations, or mature trees may require hand digging for safety, which increases labor costs.
When Underground Wiring Is Required
Some situations give you a choice between overhead and underground wiring. Others do not. Underground wiring is required in several common scenarios:
New service installations in many subdivisions. Many newer developments and HOAs in the Aiken area require underground utility feeds. If you are building a new home in a subdivision with underground utilities, your service lateral from the transformer to your meter base must be underground.
Pool and hot tub circuits. The NEC requires that electrical wiring serving pools, hot tubs, and spas follow specific underground routing requirements. Overhead wiring near swimming pools is prohibited within certain clearance distances.
Any circuit crossing a driveway, road, or paved area. Running overhead wiring across a driveway is impractical and code-prohibited in most cases. These circuits must go underground, typically in rigid conduit rated for the traffic load above.
Feeder circuits to detached structures where overhead clearances cannot be met. If trees, terrain, or building heights prevent maintaining the required overhead clearances (typically 10 to 18 feet depending on the situation), underground is the only option.
Whether your project requires underground wiring by code or you are choosing it for aesthetics and durability, the investment in professional installation pays for itself in reliability and safety. Underground wiring done correctly lasts decades without maintenance. Underground wiring done poorly can cause ground faults, tripped breakers, electrocution hazards, and expensive excavation to repair.