Animas-La Plata Water Project Proceeds in SW Colorado

After nearly four decades and countless changes, the Animas-La Plata water project in southwestern Colorado is well into construction
August 11, 2010

For almost four decades, the Animas-La Plata water project has been a subject of congressionally funded studies, public debate, presidential cancellation, congressional debate, congressional action, and congressional inaction. Many observers have commented that the project would never be built. The original congressional authorization for the Bureau of Reclamation project came in 1968 to supply 191,200 acre-feet of water for irrigation, industrial and municipal water supply use in Colorado and New Mexico. The project still had to go through design and receive the necessary permitting. It was 1980 before the final environmental impact statement was approved and released. Construction was expected to begin in 1980 or 1981, however, President Carter ordered that no new water projects be started. In 1988, the justification for the project was significantly increased when Congress passed the Colorado Ute Indian Water Rights Settlement Act resolving water right claims of the Southern Ute and Ute Mountain Ute Indian Tribes. These tribal reservations were established in the 19th century and had senior water right positions that were not given priorities in water usage.

In the decade since the environmental impact statement was completed and approved, much changed, especially with endangered species. A small fish — the Colorado Pikeminnow — threatened to make the project itself endangered, however, that problem was eventually overcome. With that obstacle removed, hope was renewed until environmental groups, seeking to totally stop the project, filed lawsuits in 1992. Those working to advance the project continued behind the scenes. In 1996, the Bureau of Reclamation released a final supplement to the final environmental impact statement recommending conditions under which the project could advance.

In 1996–97, Colorado Gov. Roy Romer and his lieutenant governor, Gail Schoettler, undertook a major initiative to bring supporters and opponents together to address and resolve the issues and gain consensus on project alternatives. The results of these meetings were two different approaches to the project, one a structural and one a non-structural approach. These meetings were amazingly successful.

In 1998, the Department of the Interior issued a recommendation for a substantially scaled-down project designed primarily to satisfy Native American water rights, along with municipal and industrial needs in the immediate area secondarily, and completely excluding other non-Indian irrigation systems. A major part of the recommendation was to comply with requirements of the Endangered Species and Clean Water acts. As part of the newly defined project, yet another final supplemental environmental impact statement and record of decision had to be prepared. These were released in 2000. Due to the fact that that the revised project would not provide benefits to the Colorado Ute Tribes identical to those defined in the Congressional authorization of 1988, Congress needed to authorize the new project to implement the 1988 Settlement Act.

Congress eventually authorized the Colorado Ute Settlement Act Amendments of 2000, authorizing construction of a reservoir, pumping plant and inlet conduit with an average annual depletion of 57,100 acre-feet from the Animas River. There is no depletion of La Plata River water, nor is there diversion authorized into the La Plata River watershed. This depletion is only of Animas River water. The Congressional authorization established a Colorado Ute Settlement Fund and appropriations to allow construction of the major portions of the project within seven years. In addition, a $40-million "resource fund" for municipal or rural water development for the Southern Ute and Ute Mountain Ute Tribes on their lands was implemented.

Present Scope of the Project

The current design, funding and project contracted or yet to bid includes the construction of a 280-cubic-feet-per-second pumping plant on the Animas River just south of downtown Durango, Colo.; an underground pipeline to carry project water from the pumping plant to the reservoir location, and an off-stream reservoir at Ridges Basin, southwest of Durango. This reservoir will store about 120,000 acre-feet of water to be pumped from the Animas River on the south end of Durango. In addition, the project includes a future buried pipeline from the Farmington, N.M., area to the Shiprock, N.M., area, supplying water for Navajo Nation usage.

It is interesting that the diverted water is removed from the Animas River for controlled discharge back into the Animas River. At this time, there is no plan or provision for the water entering any other watershed or direct discharge from the dam into any water system. Any such use facilities would have to be paid for by others. The annual water allocation is as follows:

Southern Ute Indian Tribe

33,050 acre-feet

Ute Mountain Ute Tribe

33,050 acre-feet

Animas-La Plata Water Conservancy District 5,200 acre-feet

State of Colorado 10,460 acre-feet

Navajo Nation 4,680 acre-feet

San Juan Water Commission

20,800 acre-feet

La Plata Conservancy District

1,560 acre-feet

Total 108,800 acre-feet

In addition, the reservoir has a designated permanent pool of 30,000 acre-feet for recreational, fishery and water quality purposes.

Dam Construction

Weeminuche Construction Authority of Towaoc, Colo., a Ute Mountain Ute tribal enterprise founded in 1985, has the major construction contracts for the Ridges Basin Dam, the Animas River Pumping Plant, and the connecting pipeline, under contract with the Bureau of Reclamation. Weeminuche has an excellent history of growth and performance during its history. It is not unusual for Native American tribes to establish construction enterprises, but few have grown and demonstrated such capability as has Weeminuche. A big key to the success of the business has been the professional managers and construction people it has employed. The organization operates as an open shop, however, recruitment from the tribe has been compared to calling a union hall. If workers are needed, a call is made and workers report. This is certainly easier than for most contractors. This is partially aided by the excellent reputation of Weeminuche and the relatively high unemployment among Native Americans. Weeminuche hires Native Americans from all tribes and pueblos. It is worth noting that Weeminuche has provided significant job training for Native Americans in its employment practices. Total employment by Weeminuche is approximately 260. On the Animas-La Plata Project, total employment has been approximately 300, including subcontractors. Of this number, approximately 70 percent are Native American, of which less than half are Ute Mountain Ute Tribal members.

The scope of the project is quite significant, with $219 million now under contract, all of which is with Weeminuche Construction Authority. These contracts include the Ridges Basin Dam, the Animas River Pumping Plant and the 72-inch steel pipeline connecting the pumping plant with the dam. This work has been awarded in eight separate contracts as funding and progress justified.

Construction on the project began in 2002 with a contract to install an 84-inch CMP sleeve buried approximately 40 feet below the newly relocated high-pressure gas lines crossing the project. This would later be used to thread the 72-inch steel pipeline connecting the pumping plant with the dam.

In 2005 work began on the Ridges Basin Dam, the largest key component of the project. The reservoir will be called Lake Nighthorse in honor of former Colorado Sen. Ben Nighthorse Campbell, a member of the Southern Ute Tribe. The structural height of the dam will be 275 feet, with hydraulic height or maximum water depth against the dam structure of 209 feet. The length of the dam crest will be approximately 1,670 feet, with a width of 30 feet at elevation 6,893 feet. This has been dubbed the "A-LP Lite" design. As the scope of the project was reduced, the height and cross-section of the dam was similarly reduced, lowering the impound capacity as well as material quantities and affecting a significant cost reduction.

The upstream slope of the embankment will be 2-to-1 horizontal to vertical distances from the dam crest to elevation 6,794.5, with a 20-foot-wide bench at that elevation. From the bench at elevation 6,794.5 to elevation 6,730, the slope will be 2.25-to-1. From that elevation to ground, the slope will be 200-to-1. The downstream slope will be 1.5-to-1 from the dam crest to elevation 6,700, with a break at elevation 6,785 for a 10-foot-wide bench. From elevation 6,700 to the downstream toe of the structure, the slope will be 10-to-1.

Since dams are designed to impound water, the structure must be built to minimize leakage and resist erosion by wave action and/or other forces. The dam is more than an earthfill closure of a canyon with an outlet structure. The earth below the dam must be sealed. The earthfill placed above the earth foundation is designed in zones of very selective materials to prevent leakage. If water leaks from a dam, the moving water will weaken the dam and ultimately cause problems. Zone materials are designed for various needs within the structure. Some zones provide strength against head pressure caused by major water depth. Other zones provide sealing against leakage. In addition, there are zones that resist surface erosion that might damage one of the structural or leak protection zones. This means that every cubic yard of earthfill has to be carefully produced to remove undesirable natural materials and provide the proper blend of desired materials. Then the hauling equipment must place each load in the proper zone area in the earthfill. The demands of doing this correctly make it a more difficult process than it appears to the casual observer.

The first major task was to excavate to bedrock all alluvial materials from the foundation area footprint of the dam. The maximum depth of alluvial materials removed was 90 feet. Approximately 2.4 million cubic yards of excavation was required to expose the bedrock in the required area.

The bedrock was pressure grouted in a single curtain under the section of the core that would be a zone of select clay materials. This grouting required approximately 1,300 holes totaling 51,400 linear feet of drilling. Some 28,400 sacks of cement were used in the grouting operation. On the upstream side of the embankment from the centerline the clay core would be placed with a 1-to-1 slope upstream and vertical downstream along the centerline of the dam. The clay material source is a borrow pit within the reservoir basin. Along the vertical centerline bordering the clay zone are two 8-foot-wide filter/drain zones from bedrock to the dam crest. Downstream of centerline on the bedrock, the filter/drain zone material is placed horizontally to the downstream edge of the structure. The granular filter material source is the downstream borrow area. Both upstream and downstream sides of the clay and filter/drain material zones, the remaining embankment structure consists of sand, gravel and cobbles from a downstream borrow area. The embankment quantities total approximately 5.5 million cubic yards. Above elevation 6,794.5 on the upstream side of the dam structure, riprap will protect the embankment structure from wave action erosion. Dam construction is expected to reach crest elevation in 2008.

Zone Material Production

The granular fill material is processed with a Metso screening and crushing plant that cost $12 million and is capable of a raw feed rate of 1,150 tons per hour. The plant has a grizzly to remove materials over 6 inches, two vertical shaft impact jaw crushers and two cone crushers. Due to initial testing of pit materials revealing the presence of rock encrusted with clay or other materials adhering to the rock, the rock is passed through a drum cleaner that tumbles the rock to remove such deposits. The plant is truly state of the art, with a computerized control tower and a large variety of conveyors and screens. If the balance of the plant output needs to be changed due to the materials from the borrow area being different, the changes are easily made. Materials supplied to this plant arrive primarily in articulated dump trucks, which are fed by excavators in the material pit.

The source materials are alluvial pit run gravel with soft rock and clay. The pit run material is dumped into a 150-ton live storage hopper where it is separated by a Hewitt Robins 52-inch by 24-foot vibrating grizzly removing the 6-inch-plus materials. The oversize materials are classified at Zone 6, to be placed on the downstream face of the dam and are stockpiled. Materials passing the grizzly are conveyor transferred to two Metso Svedala 8-foot by 20-foot screens where the minus 0.25-inch material is removed. The remaining 0.25-inch material is moved to a McLannahan 8-foot-diameter, 25-foot-long dry attrition drum rotating at 16 rpm, where the material is retained for four to five minutes, during which time the soft rock degrades into fines. Following this drying and rock degradation, the material is moved to another Metso Svedala 8-foot by 20-foot triple-deck screen to remove the minus 0.25-inch as well as segregating the remaining materials into two gradations: 0.25-inch to 1.5-inch and 1.5-inch to 6-inch. The smaller graded material is conveyed to a stockpile, and the minus 6-inch material is fed into a Metso HP400 cone crusher set at 1.1 inches. The output material is then fed into a Norberg 6-foot by 20-foot screen segregating the minus 1.5-inch material to a stockpile providing material to an 85-ton surge bin. From there, two FMC electromagnetic feeders, operating at 400 tons per hour each, feed two Barmac 9100 vertical shaft impact crushers. This product is then dry screened by a pair of Metso 8-foot by 20-foot screens where plus 0.75-inch and minus 0.75-inch to 0.31-inch is segregated and conveyed to a blending facility for use in Zone 3 of the dam. The minus 0.31-inch material is fed into two Metso 7-foot by 20-foot horizontal wet screens and ultimately into a wet blending facility for use in Zone 2/2A. The critical and tight specifications for Zone 2/2A call for sand filter materials without natural fines. The plant was specifically designed to meet this specification.

Outlet Works

The outlet works are located at the left abutment and include an intake approach channel approximately 1,600 feet in length, sheltering the outlet from wave action and storm surges. This channel has a 10-foot-wide bottom with 2-to-1 side slopes transitioning to 3-to-1 at the intake end of the channel. Connected to the approach channel is the intake structure, upstream tunnel, gate chamber, downstream tunnel, gatehouse, and discharge channel in sequence of water flow. The intake approach channel is connected to the tunnel portal by a 72-inch-long pipe conduit placed by open cut and cover. The tunnel is a 7.5-foot-diameter reinforced concrete-lined structure 665 feet long, built to withstand high head pressures and flow.

The gate chamber is located slightly upstream from the dam centerline and has a butterfly valve in combination with a sleeve valve in a wet well to control regular water releases. The sleeve valve design was used to assure that non-native fish would not be released alive into the Animas River, thus protecting native species. A secondary butterfly valve is installed for future pressure releases. A jet flow gate valve is in the chamber for emergency releases.

Connected to the gate chamber is the downstream discharge tunnel, which was concrete lined under a subcontract with Harrison Western Construction Co. of Lakewood, Colo., has a horseshoe cross-section and is approximately 700 feet long. It is interesting that Weeminuche performed its own tunneling, most of it with blasting. The downstream tunnel discharges water into the stilling basin, which is about 60 feet long and is designed to dissipate energy from releases of up to 500 cubic feet per second. From the stilling basin water will flow through the downstream channel, which is riprap lined, into Basin Creek with a fall of approximately 40 feet. At the creek, a headwall, reinforced concrete pipe and impact energy dissipater structure reduce the turbulent impact of the releases into the creek.

From the outlet, the creek will carry the water a distance of approximately 3.2 miles to the confluence with the Animas River. The fall is approximately 420 vertical feet in that distance. This elevation drop requires the construction of 11 earthfill drop structures with grouted riprap protection.

International Perspective

General project manager for Weeminuche Construction Authority is Steven D. Summy. He brings a long and extensive dam building resume to the project. Recently, he participated in a panel discussion at the HydroVision 2006 conference conducted by HCI of Kansas City. Approximately 2,000 delegates representing 58 countries attended the conference. Part of the information presented at that conference was the location and number of dams over 60 meters in height being built in the world. The Animas-La Plata Project's Ridges Basin Dam is the only dam of that size currently being built in the United States. Outside the United States, one is being built in northeastern Canada, one in Costa Rica, one in the Dominican Republic, and one in Puerto Rico. A significant number are also being built in China, the Middle East, Japan, and Eastern Europe. It is significant that there is such a project under construction in this region of the United States.

Pumping Plant

Just south of Durango's business center, across from Santa Rita Park, is the site of the pumping plant that will remove water from the Animas River and pump it up to the Basin Creek Reservoir. The pumping plant is located about 200 feet from the Animas River, and construction crews installed a cofferdam to protect the site from river flow. The pumping plant is designed with a 280-cubic-feet-per-second capacity with a maximum lift of 511 feet to feed the 72-inch pipeline that will carry the Animas River water to the reservoir. Also included in the project are a 40-foot-diameter steel air chamber and a 30-inch steel pipeline that will supply project water to the city of Durango directly from the pumping plant. The air chamber is to control surge pressures at the plant that could result from backflow from the pipeline.

A significant part of the pumping plant has been the excavation of materials below river bottom elevation. This was accomplished using the cofferdam as well as a secondary earthen dam. During high water flow in June 2005, the river over-topped the cofferdam and secondary dam, allowing a minimal amount of water into the construction site. According to Virgil E. Gray, project manager for the pumping plant construction, that was the time of greatest stress for the managers on that part of the project. He had a fallback plan that could have been implemented if there had been greater water inflow, however. Visualizing potential problems before they happen is clearly part of good management.

The pumping plant is very close to an old uranium mill Superfund site that was cleaned up in the 1980s. That location was slightly upstream. The pumping plant site is clear of radioactive materials, an early concern on the project.

Part of the site work involves building retaining walls with horizontal mesh to support the earth. These are necessary due to the narrow canyon with steep slopes, besides the excavation required for the site. The retaining walls also provide an element of landscape beautification, adding to the general appearance of the area.

Major quantity involved in the pumping plant is 25,000 cubic yards of concrete. The major structure work is scheduled to complete this year, at which time the installation of pumping units, electrical, and mechanical equipment and roofing will begin. Gardner Zemke Co. of Albuquerque is the major subcontractor on the project with responsibility for all mechanical and electrical work, as well as crane work. This phase of the construction will be completed in late 2008 when filling of the reservoir can commence.

Machinery Usage

Construction projects of this magnitude require incredible equipment fleets, besides the manpower to operate them. Most of the machinery utilization has been on the dam. The greatest quantity of earthmoving has been performed by nine Caterpillar excavators ranging in size from model 320 to 385 and feeding rock trucks, 10 of which are Caterpillar 60-ton rigid frame end dumps, and 11 of which are 40-ton articulated trucks, a mix of Cat and Volvo units. Four Cat 631 scrapers are also used for excavating and hauling materials. Five large wheel loaders from Cat 988 down are also in use. These primary earthmovers are supported by five Caterpillar motor graders, from 16s down; eight dozers, from a pair of Cat D9s down to a single John Deere 400; nine compaction rollers; and a Cat Challenger rubber-tracked tractor pulling discs. Also supporting the earthmoving are five water trucks and five scraper-based water wagons. Cranes, used primarily at the pumping plant, include one 200-ton, one 150-ton, one 60-ton, and a 22-ton-capacity unit. Miscellaneous but critically important equipment on-site also includes 12 air compressors, 12 water pumps, four large all-terrain forklifts, four Cat 436 backhoes, seven light towers, numerous small generators, 45 pickups, and 10 support trucks for mechanics and fuel/lubrication. In addition, several tractor-trailer rigs are available to move machinery as needed. Certainly it is an equipment-intensive project

         
 

Comments on: "Animas-La Plata Water Project Proceeds in SW Colorado "