Canal lining and piping in Idaho: what seven projects cost

What this is and isn’t

Seven canal projects in Idaho, built or under way since 2022. Every one from a state or federal record. Every dollar figure links to the document it came from.

They’re grouped by what was built. Open-canal lining is one thing. Buried pipe is another, and a 24-inch lateral isn’t a 63-inch mainline. A hardened canal running above a subdivision is a third thing again.

So there’s no average here, and no “typical cost per mile.” Those numbers get quoted a lot. They’re made by mixing products that don’t mix. What’s here instead is the spread — seven totals, seven per-foot figures, each beside the thing that skewed it.

This isn’t an estimate for your reach. It’s what the record says other reaches cost. Read it that way.

If you came for one thing:

• Open-canal lining
• Buried pipe, by diameter
• The urban case
• What drives the cost
• Cost against water saved
• How long it lasts

How to read the numbers

Three groups.

Open-canal lining. The canal stays open. A liner goes on the bed and banks. What matters is the area lined, not just the length. A 105-foot-wide canal takes far more liner per foot of length than a 20-foot lateral does.

Buried pipe. The open ditch becomes a closed pipe in the ground. Diameter drives cost more than anything else. So these are listed small to large.

Urban hardened. One project, and it stands alone. A canal running above homes gets a design the others don’t need.

Then the part every row carries: what else was in the total. A diversion structure. A control system. Junction boxes. Those aren’t padding. They’re real scope. But they’re why two projects of the same length can differ a lot per foot. Each row names them.

The per-foot figures are the total divided by the length, both as the record states them. Nothing more. They’re there so you can see the spread inside a group. They aren’t an average, and they shouldn’t be turned into one.

Some totals are final costs on finished projects. Some are estimates on work still under way. Each project’s paragraph says which.

The seven, at a glance.

Open-canal lining

Two projects. Both lined an existing canal and kept it open.

Twin Falls Canal Company — Highline Canal, Phase 2. Twin Falls County. 4,500 feet of a 105-foot-wide earthen canal, lined with 60-mil HDPE geomembrane. That’s 620,400 square feet of liner. The work included excavation, keyways to anchor the liner, and rebuilding the banks. Built winter 2023–24.

Total: $818,490. Federal WaterSMART grant $401,060. Idaho Water Resource Board Aging Infrastructure grant $245,547. Company share $171,883.

$182 per foot. Or $1.32 per square foot of liner, which is the fairer number for a canal this wide.

Conant Creek Canal Company, with the Henry’s Fork Foundation. Near Ashton, Fremont County. 5.7 miles of canal lined with two layers of 30-mil LDPE and a geotextile. The project also built a new concrete diversion structure with spillback gates. It put remote-controlled headgates on a SCADA system and added on-farm flow meters. Finished November 2024.

Total: $2,172,444. Grants: federal WaterSMART $1,122,902, state Aging Infrastructure $499,145, Idaho DEQ agricultural $165,000, two water-quality grants totaling $110,000. Plus a $90,000 state loan.

$72 per foot across 30,096 feet. But that figure carries the diversion structure and the control system, so it isn’t a liner-only number.

One note on the total. A 2023 loan memo put this project at $2,498,310. That included a $325,867 contingency. The final record reports $2,172,444 — what was spent. This article uses the final.

Buried pipe, by diameter

Four projects, small to large. Each one turned an open ditch into a closed pipe.

Teton Irrigation Canal Company — 24-inch PVC. Madison County. 2,480 feet of the 3000 North Lateral, from open earthen canal to buried pipe. The reach had a 90-degree corner eroding its bank, and seepage flooding a potato-storage building. Built December 2024 to April 2025.

Total: $175,780. State Aging Infrastructure grant $58,007.

$71 per foot.

Burnett Canal, Big Lost River Irrigation District — 30-inch HDPE. Big Lost River Valley. Eight miles of open ditch to buried pipe. This is Phase II of a larger effort. NRCS funded the first five miles, finished in 2023, as part of an 11-mile program. Phase II ran November 2024 to April 2025.

Total: $6.4 million. Grants: NRCS $2.9 million, state Aging Infrastructure $900,000, Idaho National Laboratory $500,000.

$152 per foot across 42,240 feet.

Boise Valley Irrigation Ditch Company — 48-inch HDPE. Northwest Boise, Ada County. 1,660 feet of triple-wall pipe, in two phases. The total includes reinforced-concrete junction boxes, eight feet square and seven to nine feet tall. It also covers rock-chip bedding, sand backfill, and safety capping, because the pipe runs through a city. Scheduled November 2024 to March 2026.

Total: $602,386 across both phases. Two state Aging Infrastructure grants, $105,811 and $95,794.

$363 per foot. The junction boxes and the urban setting are why.

Enterprize Canal Company — 63-inch HDPE. Ririe, northeast of Idaho Falls. 1.6 miles of buried mainline rated for 110 cubic feet per second, tied into the company’s existing network. October 2023 through 2024.

Total: $8.2 million. Grants: state Aging Infrastructure $2.7 million, federal WaterSMART $1.9 million.

$971 per foot across 8,448 feet. A 63-inch pipe moving 110 cfs is a different product from a 24-inch lateral, and the number shows it.

The urban case stands alone

New York Canal, Boise Project Board of Control. The canal is 41 miles long and carries around 2,500 cubic feet per second. Six miles of it run through the Boise area, in places perched above homes and businesses. That six miles is the project.

The design is nothing like the other six rows. A prefabricated multi-layer geocomposite membrane goes down, and a concrete cap goes over it. The cap is there because a failure above a subdivision is not like one above a field.

Total: $81.5 million, as estimated in 2024. State ARPA funding through the Idaho Water Resource Board: $50 million. Federal WaterSMART on the balance. Work started October 2024 at roughly one mile a year, with completion projected for spring 2030.

There’s no per-foot figure on this row, and here’s why. Divide $81.5 million by six miles and you get about $2,570 a foot. That’s the whole program — six years of construction, design, escalation, everything. The liner cost is a different number.

In November 2023 testimony to Congress, a Boise Project board member put the hardened design at $1,300 per linear foot. A conventional canal liner, he said, runs about $335. Nearly four times, and the testimony expected it to rise with inflation.

So: $1,300 a foot for the liner system in 2023 dollars. $81.5 million for the program in 2024 dollars. Two figures, two dates, two scopes. Neither one belongs in a range with a 24-inch PVC lateral.

If your reach runs above a neighborhood, this row is your reference. If it runs through a field, it isn’t.

What drives the cost, per the documents

Not opinion. This list comes from the agency documents themselves.

NRCS’s practice standard for ditch lining names what a liner has to be protected from. Water pressure behind it. Frost heave. Chemical reaction with the soil and water. Animal damage. Fire. It says liner thickness gets set by the engineering at each site. So the ground under the liner, and what’s in it, is a cost driver before any liner is bought.

NRCS’s practice standard for irrigation pipelines names what goes on a pipe besides the pipe. Pressure reducers and inlets. Check valves and backflow prevention. Surge tanks and air chambers. Pressure relief, air relief valves, and vents. It notes corrosion protection may be needed depending on the metal and the soil. Every one of those is a line item the pipe’s diameter doesn’t predict.

Reclamation’s canal-lining demonstration cost tables carry a note. Their unit costs assume a minimum job of 100,000 to 200,000 square feet. That’s a full truckload of liner. Smaller jobs cost more per foot, because mobilization doesn’t shrink with the job.

And the Boise Project’s testimony on New York Canal blames its four-times premium on urban expansion. Utilities, roads, homes, and the hardened materials and methods that come with them.

Put together, the documents name these:

• The material and lining system
• Pipe diameter, flow, and velocity
• Subgrade rock and chemistry, frost, and protection from animals and fire
• Valves, air and surge control, and corrosion protection
• Structures, junction boxes, and automation
• Job size and mobilization
• Urban utility, road, and safety conflicts

Which is why the rows above carry their scope notes. Two of those drivers can double a per-foot number without changing the pipe.

Cost against water saved, labeled honestly

Funders score on water conserved. So the number every application wants is dollars per acre-foot.

Three of the seven projects publish both a total cost and an estimated annual water saving. That allows a ratio. Here it is, with both inputs, every time.

Twin Falls Highline Phase 2. $818,490. The record says losses on the reach can reach about 9,400 acre-feet a season. It says more than 6,800 acre-feet will be saved. Against 6,800: about $120 per acre-foot. Against 9,400: about $87.

Conant Creek. $2,172,444. The record says the project will eliminate 2,850 acre-feet per year of seepage. About $762 per acre-foot.

New York Canal. $81.5 million estimate. The record projects about 29,370 acre-feet saved when complete. About $2,775 per acre-foot — and this is the urban outlier, so it doesn’t range with the other two.

Now the label. Each of those is one year’s capital cost divided by one year’s estimated savings. That’s all it is. It isn’t the cost of conserved water. It leaves out how long the project lasts and what it costs to maintain. It leaves out the time value of money. And it leaves out whether the estimated savings were ever measured after construction. A liner that lasts 25 years and one that lasts 10 give the same ratio here. Their real costs are very different.

No agency publishes a dollars-per-acre-foot threshold. Idaho’s Aging Infrastructure grant criteria set a competitive scoring process, not a number. Reclamation’s WaterSMART grants require a cost share and score competitively. Any per-acre-foot figure you see, including these, is a derived ratio, and it should say so.

How long it lasts, by what kind of evidence

Three kinds of number get quoted as “service life.” They aren’t the same kind.

Observed. Reclamation’s Canal-Lining Demonstration Project put test sections on three canals in Oregon’s Deschutes Basin between 1991 and 2001. The 2019 report evaluated 24 of them. Pre-lining seepage on those canals ran 35 to 50 percent. Reclamation went back at year 7 and again at year 25.

The 25-year report, from 2019, found that exposed geomembrane liners can in some cases last 25 years or more. It found concrete over a geomembrane gave the best mix of reliable performance, durability, and effectiveness. The earlier report found exposed geomembranes needed about twice the maintenance of concrete linings. It found concrete lasted well but lost effectiveness over time. A 2025 Reclamation memo restates that HDPE liners can exceed 25 years in the field without a cover.

That’s field performance. It’s also Oregon, on three specific canals. It’s the best observed data there is, and it isn’t Idaho.

Design. The New York Canal’s geocomposite-and-concrete system carries a stated life expectancy of 50 years. That’s the owner’s design claim for that system. It hasn’t been observed, because the first mile went in two years ago.

Program. NRCS’s practice standard for irrigation pipelines states a minimum expected life of 20 years. That’s the lifespan the program plans around, not a measurement of any particular pipe.

When a vendor quotes a service life, ask which kind. Observed on what, designed by whom, or a program planning figure.

Before you spend it

Seven projects. $175,780 at the small end, $81.5 million at the large. Every one of them tied to a specific reach that somebody chose.

Line the wrong reach and the liner performs fine while the seepage carries on somewhere else. Pipe a lateral that wasn’t losing much, and the acre-feet on the application never show up in the measurement. The construction can be perfect and the project still wrong.

Choosing the reach is the decision the money rides on.

The record above shows what the money is. Finding the reach is a different question. We’ve written about one way to narrow it: How dawn thermography narrows the search for canal seepage. And if you’re weighing which reaches to line, the canal decision page lays out where that fits.

If you’re pricing a reach

A short call covers three things. Which reaches are candidates, and what you already know about where the water goes. What kind of construction you’re weighing, so the right rows above apply. And what the funding file needs, so the work ahead of the lining decision produces what the application asks for.

We’re owner-operated. The person you talk to is the person who does the work.

If you already know where the reach is leaking, it doesn’t need a thermal look first. We’ll say so.