Which way the rule points, and why summaries flip it
Almost every distance written down about wells binds the well. It is a rule about where a new well may be drilled, measured out to whatever is already sitting on the property. It is not a rule about where you may pour concrete beside a well that has been in the ground since the house was built. Those are two different questions, and a summary that drops the direction quietly turns one into the other.
Virginia says which one it is in the text. 12VAC5-630-30 B reads, "This chapter applies to owners of a private well." Subsection B of 12VAC5-630-380 sets its distances between a private well and whatever sits near it, its sanitary survey sentence speaks of "the proposed private well," and subsections E, G, H, I and J all open the same way, no private well shall be constructed within so many feet of something. North Carolina says it even more plainly at 15A NCAC 02C .0107(a)(2), where the distances are measured to "potential sources of groundwater contamination that exist at the time the well is constructed."
So when you read that a well has to sit 50 feet off a septic tank, that is the driller's problem on the day the well goes in. It does not become your problem on the day you pour a patio. Where new concrete does get tied to something already in the ground, it is the septic system rather than the well, and North Carolina is the state that says so plainly. Virginia gets at the same ground from a different angle, through its rule on what may sit over a drainfield. Both are further down this page.
Virginia does not publish a number for concrete near a well
Table 1 of 12VAC5-630-380 is the table Virginia uses to set how far a new private well sits from structures, topographic features and sources of pollution. It carries rows for building foundations, sewerage systems, septic tanks and aerobic units, drainfields, permanently abandoned sewage systems, cemeteries and property lines. It carries no row for a driveway, a patio, a sidewalk, a slab, pavement or any impervious surface at all. The only built thing on the whole table is a building foundation, at 15 feet, or 10 feet where the structure is treated with a borate based termite treatment, and a building foundation is a building, not flatwork.
There is no local version to go check either. Code of Virginia section 32.1-176.4 A names the specific localities allowed to adopt their own well construction standards, and section 32.1-176.5 B names the ones allowed to require water testing before a building permit. Carroll, Grayson, Wythe, Floyd, Patrick, Pulaski, Montgomery, Giles, Smyth and Roanoke counties and the City of Galax appear on neither list. Around Hillsville the state rule is the only rule, so a distance printed on a county handout is either a restatement of the state rule or it is wrong.
Virginia does write down one thing a slab can work against, and it is about water rather than distance. 12VAC5-630-390 C says, "The area around the well shall be graded to divert surface water away from the well." North Carolina has the twin of that sentence at 15A NCAC 02C .0107(j)(6). Neither rule mentions concrete or slabs, so take this as practical advice from a crew and not as a code requirement on your patio: if the finished concrete sheds toward the casing, the grade now carries surface water to the one spot both states bothered to write a rule about. Pitching it the other way costs nothing at form time, and we set fall on every slab anyway.
North Carolina puts its distances in writing, and they are small
North Carolina's well rule does carry a figure that touches concrete. 15A NCAC 02C .0107(a)(2)(P) sets 25 feet for "Building perimeters, including any attached structures that need a building permit, such as garages, patios, or decks, regardless of foundation construction type." Check the direction one more time. That 25 feet binds a well being constructed, and an attached patio or deck that needs a building permit counts as part of the perimeter the driller measures from.
The numbers that bind new concrete to something already in the ground live in the septic rules instead. Table IX at 15A NCAC 18E .0601(a) sets one foot from a wastewater system for "sidewalks; pavers; lighting fixtures; or signage" and for landing structures designed to be set directly on the ground that do not require footings, and five feet for "Building foundation and any structural supports requiring a footing or other load bearing construction in the North Carolina Building Code." One foot and five feet. Whether the concrete needs a footing is the entire difference between those two rows.
Two more North Carolina rules matter, and both point at the property owner rather than at the crew. 15A NCAC 18E .0206 makes "a site modification that requires a building permit" the trigger for an existing system approval, the test at .0206(b)(3) is whether the modification meets the Section .0600 setbacks, and subsection (g) says the owner is responsible for making sure it does. And 15A NCAC 18E .1303(a)(7), which prohibits activities that result in soil disturbance or soil compaction over the initial and repair dispersal field area, reaches every wastewater system in the state, because rule .0102(f) pulls Section .1300 back over systems permitted before January 1, 2024 that .0102(a) otherwise exempts from most of the subchapter. Our work south of the state line gets laid out around those two.
The drainfield rule is the one that really exists, and in Virginia it names concrete
12VAC5-610-700 E.1 is one short subsection carrying three different rules, and it is easy to collapse into a flat "you can never pave over a drainfield," which is not what it says. Structures over the subsurface soil absorption system are prohibited outright, no conditions. Driveways and parking lots over it are conditional, and Virginia spells the conditions out: the invert of the lead or header lines or the top of the gravel in the absorption trenches has to be deeper than 30 inches below the ground surface, and the driveway or parking lot has to be "paved with portland cement or bituminous concrete to prevent compaction of the trench bottom."
Read the reason the Board gives. The worry is compaction of the trench bottom, and the regulation names properly placed paving as the thing that prevents it. That is a rare case where concrete is the mitigation instead of the offense. The distribution box gets its own sentence and its own condition: driveways and parking lots shall not be constructed over it "unless adequate structural and access provisions are provided," and the regulation never defines adequate. The same section also reaches wheeled and tracked vehicles crossing the field before, during and after the trenches go in.
Neither condition can be settled from the yard. Nobody can tell you from the surface how deep those trenches run or where the distribution box sits. Both facts are on the permit and the record drawing at the health department. That is why this question ends in a phone call rather than a tape measure, and why we would rather have the answer before a truck is ordered than after.
The reserve area, which is the expensive mistake
In North Carolina a permitted septic system is supposed to have somewhere to go when it quits, and a site without room for both an initial system and a repair area is unsuitable. North Carolina calls that space the repair area and defines it at 15A NCAC 18E .0105(88) as an area "reserved for the extension, alteration, wastewater system relocation, or replacement of part or all of the initial wastewater system," available if the system is partially or totally destroyed. Rule .0508(h) forbids altering the initial and repair area so that the permitted system can no longer be installed and function as permitted, and .0601(f) says an initial or repair dispersal field shall not be located under impervious surfaces or areas subject to vehicular traffic unless the system is approved under G.S. 130A-343 and Section .1700, which turns on what type of system it is rather than on a variance a homeowner can go ask for.
Virginia reaches a similar place by a different road, and the difference is worth stating honestly. 12VAC5-610-710 requires a reserve equal to 50 percent of the required absorption area where the estimated or measured percolation rate exceeds 45 minutes per inch, and 12VAC5-610-500 requires enough suitable soil on the site for both the system and the reserve. But Virginia's paving rule at 12VAC5-610-700 E.1 names the subsurface soil absorption system and does not name the reserve. So we will not tell you Virginia bans paving over a reserve area. The text does not say that, and a rule nobody can open is not a rule.
The practical risk is the same in both states, and it does not depend on which regulation reaches furthest. When a drainfield fails, the replacement goes in the reserve, and the replacement has to clear every separation distance over again. If a slab is sitting on the reserve by then, the homeowner is choosing between tearing out concrete and paying for an engineered alternative system. A driveway poured across the wrong strip of yard costs nothing on pour day. It costs on the day the field gives out, which may be years later and is not a day anybody plans for.
Who holds the answers, and the three things to ask
In Virginia both the well permit and the sewage permit belong to the local health department, and the records go with them. Carroll County Health Department, 276-730-3180. Grayson County Health Department, 276-773-2961. Wythe County Health Department, 276-228-5507. Floyd County Health Department, 540-745-2142. Carroll, Grayson and Wythe counties and the City of Galax sit in the Mount Rogers Health District. Floyd, Giles, Montgomery and Pulaski counties sit in the New River Health District. In North Carolina the local health department serving the county is the permitting authority for both, under G.S. 87-97(a) for wells and 15A NCAC 18E for wastewater.
Ask three things. How deep the drainfield trenches run. Where the distribution box sits. Whether the lot carries a reserve or repair area, and where it is. If the well itself is close to the layout, the well class is worth asking too, because the 50 foot and 100 foot figures in Virginia's Table 1 turn on casing and grout depth rather than on how old the well is. None of that is guesswork we can do for you from the driveway.
One more thing worth knowing before you start making calls: this is a separate desk from the building office. Virginia says so at 12VAC5-630-70, which makes the well chapter "independent of and in addition to" the Uniform Statewide Building Code and requires anyone who needs a well permit to furnish a copy to the local building official, on request, when applying for a building permit. So a yes from one desk is not a yes from the other, and the county building permit runs on its own track.