The short answer.
A targeted drainage fix on a Hill Country residential property typically falls between $2,500 and $14,000 for the scope most homeowners face — surface water that's pooling, runoff that's eating beds, downspouts that are dumping at the foundation, or a low spot turning into a mosquito factory after every storm.
Full property regrading with engineered drainage runs higher — $14,000 to $40,000+ depending on acreage, rock content of the soil, and how much hardscape ties into the system. Bioswale systems with native plant filtration sit in the $6,000–$18,000 range when designed as a standalone scope.
Those are wide ranges because drainage is one of the most site-specific services we install. The factors below explain why.
What drives the price up or down.
Rock content of the soil. Bulverde, Boerne, Cordillera Ranch, and Spring Branch all sit on caliche limestone shelves. A trench that takes 20 minutes in New Braunfels clay can take 4 hours in Spring Branch caliche. We don't trench-shop — we look at the soil, sometimes test-dig, and quote based on what's actually under the surface.
Linear footage of drain line. French drain in the Hill Country runs roughly $32–$48 per linear foot installed (pipe, fabric, gravel, excavation, and tie-in). Channel drain at hard surfaces — patios, driveways, pool decks — runs $95–$165 per linear foot because of the cutting and bedding work.
Outlet and discharge point. If water can daylight to a natural drainage swale within 30 feet of the problem, the system is cheap and clean. If it has to be routed across a property to a public right-of-way or a constructed dispersion field, that adds significant labor.
How much hardscape it interacts with. Cutting into an existing flagstone patio to install a channel drain is expensive. Designing the drain into a new patio install is almost free by comparison. The cheapest time to engineer drainage is during the hardscape build.
Slope and topography. Canyon Lake properties with 15%+ slope often need stepped drainage with intermediate catch basins. That's a different scope than a flat half-acre in Garden Ridge.
Typical line items in an honest proposal.
Every drainage proposal we write itemizes the work the way it'll get billed:
- Site walk + drainage map — included free in the proposal phase
- Excavation — by the linear foot or by the cubic yard, depending on scope
- Drain pipe — 4″ corrugated perforated or solid SDR, priced per foot
- Drainage fabric — non-woven, by the foot of trench
- Drainage gravel — washed #57 or pea gravel, by the cubic yard
- Catch basins / grates — by the unit, with brand and inlet size specified
- Tie-in to existing downspouts — by the connection, including any flex pipe and adapters
- Outlet headwall or daylight emitter — by the unit
- Restoration — sod, mulch, decomposed granite, or other surface back-fill
- Permits if applicable — rare for residential but flagged when relevant
If a competing proposal says "drainage system: $X,XXX" with no line items, ask for the breakdown before you sign anything. Lump-sum drainage proposals are how surprise change orders get born.
What we won't quote without walking the property.
Anything past surface-level grading. The reason: caliche depth varies by 6+ inches within a single property in this region. We've test-dug Bulverde lots where one corner hit limestone at 4 inches and the other corner went 18 inches before refusal. That's the difference between a $4,000 quote and a $9,000 quote.
Phone quotes on drainage in the Hill Country are guesses. We don't do them. The walk is free.
Common scenarios and rough budgets.
Foundation downspout integration (4 downspouts, 60′ run, daylight outlet) — usually $2,400–$3,800.
Single low-spot French drain (40–60 linear feet, single catch basin, outlet) — typically $3,500–$5,500.
Channel drain across a flagstone patio (20 linear feet, tied to a French drain run) — $4,800–$7,500.
Side-yard regrade + French drain + downspout tie-in (100+ linear feet) — $7,000–$12,000.
Bioswale system with native filtration plantings — $6,000–$18,000 depending on length and plant scope.
Full property drainage redesign on a steep Canyon Lake or Spring Branch lot — $15,000–$40,000+.
Ranges assume no major hardscape demolition. Cutting into existing concrete or removing mature plantings adds line items.
Why a free walk is worth it.
Most properties don't need the biggest scope. A lot of them just need one well-placed catch basin and a clean outlet — $3,000 of work that prevents $15,000 of foundation repair or fire-ant pressure or dead beds three years from now.
The only way to know which is which is to walk it. That part is free. The proposal is itemized and locked for 14 days.