ALTOONA, Pa. (AP) — It's an ornament within the often-photographed view that includes the necklace of the Horseshoe Curve.

But the reservoir complex enfolded by the famous stretch of railroad tracks is far more: The city of Altoona may owe its very existence to those bodies of water and to the engineer who designed critical protections for the resource they collected.

Those innovative protections, created in three phases more than a century ago and still in use, have earned the three-reservoir complex status as a "Landmark" North American system from the American Water Works Association — one of two systems so named for 2018.

It's all interlaced: The Pennsylvania Railroad built its main shops for repair and fabrication near the Curve, which is halfway up the Allegheny Front, and likewise built the City of Altoona around those shops to house the workers needed to operate them, according to Mark Glenn, president of Gwin Dobson & Foreman, consulting engineer for the Altoona Water Authority, which operates the reservoir complex, part of a larger system that serves Altoona.

The shops needed lots of water, and ultimately, the railroad built reservoirs in all the hollows but one along the Allegheny Front between Tyrone and Hollidaysburg, to supply its thirsty operations with water for foundry work, steam engines, quenching and more, said Glenn, who documented the Curve complex engineering to earn the Landmark designation.

The city exploited the one remaining hollow, the one with the largest watershed, where Glen White Run and Kittanning Run come together to form Burgoon Run, to get the water it needed to sustain the families of the workers, according to Glenn.

The city finished its initial sizeable reservoir there, just below the Curve, 65-million-gallon Kittanning Point, in 1888, but it was plagued almost immediately by soil, rocks, branches and pollutants from the mountains above it, which released those materials freely when it stormed — having been denuded of timber and mined for coal to supply resources needed by the shops and the city.

"A storm in 1894 deposited 20,000 cubic yards of debris in one day alone," Glenn stated in a book he submitted to the AWWA for the Landmark designation. "The net effect was dwindling reservoir capacity and impaired water quality."

An aptly named, self-taught engineer from Rome, N.Y., Charles Knight, came to the rescue of the city in distress like a medieval hero by designing a levee and inlet system to protect the reservoir.

The levee caught the water that came down from the mountains and diverted it around the reservoir, along a bypass channel that parallels current-day Kittanning Point Road. A grate with a valve on the Glen White Run side of the confluence allowed reservoir operators to admit all of the normal, relatively clean flow of the stream into the reservoir, while a similar grate with valve on the Kittanning Run side allowed operators to admit the less-clean normal flow of Kittanning Run to the reservoir also when needed.

During a storm, when the water from both streams was turbid and full of debris, those valves would be closed and the water would pass around the reservoir and go downstream and away harmlessly in Burgoon Run.

An overflow notch on the channel allowed egregious excess from severe storms to spill into the reservoir, to protect structures downstream.

In times of drought, when any kind of water was scarce, the operators could admit water from both streams to refill the lake, even if it was not close to being ideally clean.

The protections worked, but the city was growing and Kittanning Point reservoir didn't store enough.

So officials decided to build another dam to create a reservoir downstream.

To protect the water held back by the proposed new Impounding Dam, Knight extended the bypass levee around Kittanning Point reservoir for another 4,500 feet, creating a lined channel 20 feet wide, with the sides sloped back at 45 degrees.

Stonecutters were brought in from as far away as Massachusetts and Indiana, and the job was completed in four months in 1897 — the same year the Impounding Dam was completed.

The fine-grained sandstone came from a quarry near Dysart, and it has held up remarkably well to the acid mine drainage in the water coming down from the mountain, Glenn said.

The masons cut the stone by hand, with hammers and chisels, and placed them using only a minimal amount of mortar, he said.

They laid the stones for the floor of the channel on a bed of concrete.

In recent times, engineers have checked the slope of the channel and determined that it's a perfect 2 percent downgrade, Glenn said, standing last week on the green-painted steel-grate bridge that crosses the channel just downstream from Kittanning Point.

"This remarkable example of 19th century workmanship has stood the test of time, showing no signs of deterioration," Glenn wrote in his citation, speaking also of the initial Kittanning Point bypass.

After completion of the Impounding Dam, the city continued to grow, and droughts continued to occur, so officials again looked for an additional water source in 1904.

They proposed a reservoir in Tipton hollow, but the railroad fought it, so officials decided to add a third in-line reservoir in Burgoon hollow, bigger than the other two.

"The city decided to stick to this watershed," said Glenn, standing on the breast of the Impounding Dam last week.

There was a problem, though.

If workers tried to extend the bypass to the left of the projected basin of the new reservoir, they would have needed to build a Roman-style aqueduct to take the bypass water over an intersecting stream coming in from the left — decent-quality Scotch Run, Glenn said.

The downslope of the terrain below the Impounding Dam wasn't great enough to allow sufficient elevation for such an aqueduct, Glenn said.

So Knight conceived and executed a bold solution that involved a tunnel, a small dam to create a settling basin and an extension of the open bypass channel.

A 1,275-foot long, 9-foot-diameter tunnel began just to the left of the Impounding Dam and took the bypass water through a hill to Scotch Run, about half-a-mile upstream from its confluence with the projected basin of the proposed reservoir.

Workers built the small dam about 200 yards from the tunnel outlet, just above where Scotch Run would enter the basin of the proposed reservoir, to create a settling pond for the mixed waters of Scotch Run and the bypass tunnel.

The 2,200-foot concrete bypass extension beyond the settling pond dam took the water from the settling pond around the edge of the new reservoir — which became 800-million-gallon Lake Altoona — to beyond the Lake Altoona dam, sending it harmlessly down Burgoon Run.

A grate and valve at the head of the bypass extension allowed operators to admit water from the settling pond — presumably cleaner for the sediment having settled out — to Lake Altoona.

The grate and valve opening has since been closed, as there is no longer a need for that water.

Back at the settling pond dam, over which Kittanning Point Road still runs, a pair of high weirs admitted water from severe floods directly to the new reservoir, to protect structures downstream.

Even further back, at the head of the tunnel, a hump in the bypass channel allows high flood water to enter the spillway of the Impounding Dam, to prevent overflow onto Kittanning Point Road.

The settling pond dam itself no longer looks like a dam, because the lake behind it has filled in, and the stream — the mix of bypass water and Scotch Run — passes through unimpeded to the bypass channel extension around Lake Altoona.

Largest source

The three-reservoir complex at the Curve is the Altoona Water Authority's largest source of water and its most dependable supply, according to Tobias Nagle, the authority's water treatment supervisor.

At this point, all incoming water for all three in-line reservoirs comes through the grate and valve setup for Glen White Run above the Kittanning Point reservoir, Nagle said.

The quality of Glen White Run water is fairly good, because of a system of passive acid-mine-drainage treatment facilities on the mountain, he said.

The grate and valve setup for Kittanning Run is semi-permanently closed, because that stream's water quality is not good, Nagle said.

Kittanning Run water makes up all the normal flow in the bypass channel, until it mixes with Scotch Run water below the tunnel, he said.

Just a couple of weeks ago, the authority began talks with the state Department of Environmental Protection on the potential for installing passive treatment facilities in the Kittanning Run watershed, Nagle said.

Realizing those facilities is a long way off — probably decades — and will depend on political effort, Nagle said.

But if it should happen, it would virtually make the authority's overall system drought-proof, as Kittanning Run's volume is at least equal to Glen White Run's, he said.

Cleaning up Kittanning Run would mean the bypass channel would be empty of bad-quality water, which would mean also that the water of Scotch Run could be admitted to Lake Altoona by opening up a line in the bypass channel extension.

The authority's water system is already close to being drought-proof, as it includes the Little Allegheny and Mill Run reservoirs and Homers Gap reservoirs, all built by the city — plus Tipton, Bellwood, Blair Gap, Plane 9 and Kettle reservoirs, all built by the railroad. Muleshoe Reservoir is owned by Hollidaysburg but contributes water to the authority's Plane 9 treatment plant.

The protections established by Knight at the Curve reservoir complex enable the authority to seal off the reservoirs from contamination should there be a traffic or railway accident upstream that causes a spill of hazardous liquids, Nagle said.

The entire Curve reservoir complex was constructed for $850,000 and all financed with public bonds, Glenn said.

"(The citizens who paid for the work) wanted clean, safe, reliable water," he said.

There was intense interest at the time in water and sewer works, given their capacity to diminish the threat of diseases like cholera and typhoid, Glenn said.

The complex would cost about $85 million to duplicate today, Glenn said.

"It's elegant, but functional," Glenn said of the complex. "Being an engineer, I can appreciate these kinds of solutions."

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Information from: Altoona Mirror, http://www.altoonamirror.com