Carlsbad Irrigation District, McMillan Dam, On Pecos River, 13 miles north of Carlsbad, Carlsbad

Source document Quoted word for word from HAER NM,8-CARL.V,1A-. Not written, edited or summarised by this site.

On the Pecos River 13 miles north of Carlsbad Carlsbad vicinity Eddy County, New Mexico The McMillan Dam is located at latitude: longitude: This point was obtained on June 18, using Google Maps There is no restriction on its release to the public. Present Owner/Occupant: U.S. Department of the Interior, Bureau of Reclamation (Reclamation) Upper Colorado Region Albuquerque Area Office 555 Broadway NE, Suite 100 Albuquerque, New Mexico

Source document Quoted word for word from HAER NM,8-CARL.V,1A-. Not written, edited or summarised by this site.

The Carlsbad Irrigation District (CID) is nationally significant as a major engineering feat to divert water from the Pecos River for delivery to farmlands via a complex irrigation system composed of dams, flumes, siphons, canals, and laterals. It represents broad national patterns of U.S. history and is an outstanding example of late-nineteenth-century engineering. Furthermore, it is representative of the themes of agriculture and agriculture as a business enterprise beyond self-sufficiency. The McMillan Dam and its appurtenance works help to convey this significance. The CID was designated a National Historic Landmark in In the NHL was designated a National Register of Historic Places historic district.2 Historians: Scott Thompson and Holly Borth Statistical Research, Inc.

Albuquerque, New Mexico July

Source document Quoted word for word from HAER NM,8-CARL.V,1A-. Not written, edited or summarised by this site.

This documentation was completed in under a memorandum of agreement between Reclamation and the New Mexico State Historic Preservation Officer after Reclamation caused damage to the McMillan Dam Complex by demolishing the Garage/Boat House, Gate House, and CCC 1 Scott O Mack, Matt C. Bischoff, and Amanda Gronhovd, The Canals of Carlsbad: Historical and Archaeological Evaluation of the Carlsbad Irrigation District Distribution System, Technical Report (Tucson, AZ: Statistical Research, 2 Mark Hufstetler and Lon Johnson, Carlsbad Irrigation District, National Register of Historic Places Registration Form (Washington, DC: U.S. Department of the Interior National Park Service, CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No.

NM-4-A (Page 2) masonry wall, which caused an adverse effect to the Gate Keeper s House, the Gate House and Outlet Works, the Garage/Boat House buildings and numerous sites/features within the McMillan Dam Complex. Reclamation contracted with Statistical Research, Inc. (SRI), to record the structure in accordance with the standards for HAER Level II documentation. Mr. Scott Thompson conducted the archival research and field investigations for this project in June and, with assistance from Ms. Holly Borth, wrote and compiled this report. CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 3) Part I. Historical Information A. Physical History 1. Dates of construction: 2. Architect/Engineer: Louis D.

Blauvelt (chief engineer) oversaw the design and construction of McMillan Dam.3 3. Builder/Contractor/Supplier: The Pecos Irrigation and Investment Company s (PIIC s) own labor force carried out the construction of the dam and its appurtenant works.4 4. Original Plans and Construction: McMillan Dam was designed and constructed by the PIIC at an estimated cost of Completed in the dam and outlet structure were built at a location where limestone bluffs converge to narrow the width of the Pecos River Valley. As constructed, the water-storage and water-control resource consisted of a rockfill dam faced with a layer of impervious earth. When completed, the dam had a length of a maximum height of a crest width of and a bottom width of The Outlet Works (HAER No.

NM-4-A-1), located at the east end of the dam, originally consisted of a wood headgate set between cut-stone walls. Six wood gates, each measuring 4' x 8', were raised and lowered by screws. Water discharged through the gates emptied into an outlet channel measuring in length that was excavated through solid limestone. The channel, in turn, discharged the water into the Pecos River below the dam. Other elements associated with dam operations included a Gate Keeper s House (constructed ca. (HAER No. NM-4-A-2) and a combination garage and boathouse that was built in the 5. Alterations and Additions: In addition to routine maintenance and repair activities, five major alterations have occurred.

In the headgate structure located at the east end of the dam and originally constructed of wood was replaced by a reinforced-concrete headgate structure. Following a flood in Reclamation raised the height of the dam by 3'. This was accomplished by constructing a hand-laid rock wall against the upstream face of the dam and raising the height by adding compacted earth to the top of the wall. To repair leaks in the rockfill dam caused by a flood in Reclamation dug a trench 13' deep across the crest of the dam and filled it with puddled clay mixed with gravel. Two spillways were constructed in to further protect the dam from seepage and erosion.

During the period the Civilian Conservation Corps constructed a 98' long concrete apron on the downstream side of the Outlet Works to prevent the flow of water from undercutting the structure. CCC crews also built rock walls across the crest of the outlet structure, along the road leading to the Gate Keeper s House, and around the Gate House.6 3 Historic American Engineering Record (HAER), National Park Service, U.S. Department of the Interior, Carlsbad Irrigation District, HAER No. 37. 4 HAER, Carlsbad Irrigation District, 36. 5 HAER, Carlsbad Irrigation District, 36 38. 6 Mark Hufstetler and Lon Johnson, Watering the Land: The Turbulent History of the Carlsbad Irrigation District (Denver, CO: U.S.

Department of the Interior National Park Service, Rocky Mountain Region, Division of National Preservation Programs, Hufstetler and Lon Johnson, Carlsbad Irrigation District, 2 3. CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 4) B. Historical Context The CID Non-native farmers and entrepreneurs began constructing irrigation features in the Pecos River valley in the late Instrumental in these early efforts were Pat Garrett, former sheriff of Lincoln County, New Mexico; Charles B. Eddy, a successful cattle rancher with a spread on the lower Pecos; Charles W. Greene, a southwest newspaperman with experience as an active entrepreneur; and Robert Weems Tansill, a local farmer and businessman attributed as the inventor of the cigar band.

Together, they incorporated the Pecos Irrigation and Improvement Company in to develop a large-scale reclamation program along the Pecos River.7 By the Pecos Irrigation and Improvement Company had received the backing of John Hagerman, a wealthy businessman from Colorado Springs, Colorado. With Hagerman s financial support, the Pecos Irrigation and Improvement Company began constructing Avalon Dam and its associated canal system running along both sides of the Pecos River. Owing to Hagerman s experience and connections, three engineers came down from Colorado to design the system: Cloud and his two assistants, Louis D. Blauvelt and Edwin S. Nettleton.

Under their efforts, these first irrigation works were simple in design with unlined canals; the simplicity of the designs was intended to allow the system to open that same year, and they were largely completed by the end of Inspired by the potential he saw in the Pecos Irrigation and Improvement Company and the Pecos Valley, Hagerman headed a reorganization of the business entity that created the Pecos Irrigation and Investment Company (PIIC), which was able to purchase and own land that the other irrigation company could not.

The PIIC quickly realized that Avalon Dam was far too small to provide the water reserve needed for the canal system, and thus construction of McMillan Dam commenced in it was completed in Unanticipated floods that destroyed Avalon Dam, erratic river flow, inadequate water storage, and low agricultural prices all contributed to the failure of the PIIC efforts by the mid-1890s. With his expectations going unmet, Hagerman began to withdraw his financial support, proving a near-fatal blow to the irrigation system.10 Although the PIIC irrigation system was able to resume operations for the growing season, the Pecos River Valley continued to experience economic hardships through the rest of the decade.

These hardships were somewhat related to the economic problems of the nation, but local conditions were also contributing factors. The valley's farmers had experimented with a variety of crops, but most had not proven economically viable, and those crops that were grown proved difficult to market. Due to these factors, the PIIC joined the ranks of most other large corporate irrigation efforts in the West and declared bankruptcy. By approximately 90 percent of these companies were in or near bankruptcy.11 7 Mark Hufstetler and Lon Johnson, Watering the Land: The Turbulent History of the Carlsbad Irrigation District (Denver, CO: U.S.

Department of the Interior National Park Service, Rocky Mountain Region, Division of National Preservation Programs, 16; O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 6. 8 Hufstetler and Johnson, Watering the Land, 24 27. 9 Hufstetler and Johnson, Watering the Land, 39. 10 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 6. 11 Hufstetler and Johnson, Watering the Land, 43. CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 5) In under the leadership of Francis G. Tracy, the PIIC was reorganized as the Pecos Irrigation Company (PIC).12 The PIC became marginally profitable after its reorganization, but by the next year, any optimism began to fade as management realized that substantial improvements to the system would soon be necessary.

By Tracy and Tansill recognized that the Pecos River flume at Avalon Dam needed immediate replacement and that any future expansion of the system hinged on a reduction of the canal network's substantial seepage problem in the canals and McMillan Reservoir. The magnitude of these projects suggested that the company's investors would be better served if a buyer for the entire system could be found.13 The federal government had expressed interest in the irrigation potential of the lower Pecos River Valley as early as when Wyoming State Engineer, Elwood Mead, conducted investigations of the area on behalf of the Department of Agriculture. Mead recommended several measures to improve the viability of the system, the most noteworthy being the lining of the canals with concrete.

As a result, Carlsbad area landowners formed the Pecos Valley Water Users Association (PVWUA) to obtain federal support for irrigation along their stretch of the river.14 In the U.S. Congress passed the Reclamation Act, which established the U.S. Reclamation Service (later renamed the Bureau of Reclamation). Another flood in destroyed much of what had been constructed by the private irrigation interests in the Carlsbad area, including Avalon Dam for a second time. Tracy ran into problems as the result of the floods, as investment bankers were not willing to finance reconstruction of the system.

The PVWUA immediately began a lobbying effort to obtain government acquisition of the system.15 After almost an entire year of negotiations, Reclamation officially purchased the PIIC system, renamed it the Carlsbad Project, and authorized much needed repair work to commence.16 Included in the repair work was a series of dams, canals, laterals, and water-control features.

Avalon Dam was completely reconstructed, and the Pecos River Flume and the Dark Canyon Siphon were rehabilitated.17 Reclamation s management of the Carlsbad Project brought a continued presence of rehabilitation and improvement to the project elements, leading to relative operational stability by the and through the A program to line many of the laterals with concrete got underway beginning in and continued as a part of general maintenance and upkeep of the system. By approximately acres of irrigable land were in private hands.19 During the the Great Depression left more than 25 percent of the nation s population out of work; in the Pecos River Valley, crop values dropped from $30 to below $20 per acre.

Federal programs such as the Works Progress Administration, Civil Works Administration, and Civilian Conservation Corps sought to provide relief in the form of large, federally financed projects. The Carlsbad Project hosted two CCC camps and which had a significant impact on the project infrastructure.20 Work completed by the CCC included the much-needed lining of at least thirty-two miles of canals and laterals with concrete and stone. The CCC completed other various improvements, including but not limited to: 12 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 6. 13 Hufstetler and Johnson, Watering the Land, 54. 14 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 6. 15 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 6 7. 16 Hufstetler and Johnson, Watering the Land, 85.

17 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 7. 18 Hufstetler and Johnson, Carlsbad Irrigation District, 19 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 11. 20 Hufstetler and Johnson, Carlsbad Irrigation District, 27. CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 6) reconstructing parts of McMillan Dam, lining and constructing drains, building embankments, and controlling rodents.21 The government s commitment at that time allowed for the achievement of one major Carlsbad Project goal in particular: constructing the Fort Sumner storage dam about 160 miles upstream from Carlsbad. Originally named Alamogordo Dam, Fort Sumner Dam was approved in as a work relief project and received a $1 million appropriation under the Emergency Relief Appropriation Act.

The construction contract was awarded to the Hallett Construction Company of Crosby, Minnesota, which began construction on March 5, Completed in Fort Sumner Dam provided much-needed irrigation storage to Carlsbad and replaced McMillan Reservoir as the irrigation project s primary reservoir.22 On October 1, in accordance with the Reclamation Act of the CID (successor to the PVWUA) officially assumed operation of the Carlsbad Project. Reclamation retained ownership of the water-storage and water-conveyance facilities of the CID and operational responsibility of Fort Sumner Dam; the CID only inherited operational responsibilities.23 Agricultural production and prosperity rose during the remainder of the By the early there were 400 farms in the district, farming roughly irrigated acres.

The principal crop was cotton, although alfalfa and barley were also grown. There were approximately 151 miles of laterals, twenty-four miles of drains, and thirty-seven miles of canals.24 During the late and into the the CID and Reclamation cooperated on a massive rehabilitation and betterment program.25 Despite all their previous efforts, McMillan Dam continued to inhibit the irrigation system s storage capacity, and concerns over its structural safety persisted. In Reclamation prepared a Safety and Evaluation Study of McMillan and Avalon Dams, which concluded that a potential flood would exceed existing spillway capacity and cause McMillan Dam to be overtopped, which in turn would cause failure of both McMillan and Avalon Dams.

Reclamation research on possible solutions culminated in a report that ultimately proposed replacing McMillan Dam and Reservoir with a new dam located between McMillan and Avalon Dams.26 In October Congress passed Public Law which authorized the construction and future operation of Brantley Dam and Reservoir. Brantley Dam and Reservoir construction also received in federal funding. Due to continuing discourse between Reclamation, Congress, and the CID, the Monterrey Construction Company did not actually begin constructing Brantley Dam until and it was completed in Brantley Dam s completion allowed for McMillan Dam to be breached, although it remains extant into the present day.

The CID continues to operate in its originally conceived capacity, providing irrigation water to approximately acres of farmland in the Carlsbad area.28 21 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 11 15. 22 Hufstetler and Johnson, Watering the Land, 141 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 15. 23 Hufstetler and Johnson, Carlsbad Irrigation District, O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 15. 24 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 15. 25 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 22. 26 Hufstetler and Johnson, Watering the Land, 147 27 Hufstetler and Johnson, Watering the Land, 28 O Mack, Bischoff, and Gronhovd, Canals of Carlsbad, 22. CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No.

NM-4-A (Page 7) McMillan Dam Construction of McMillan Dam commenced in to increase the overall storage capacity of the irrigation system. The PIIC considered both earthfill and rockfill dam designs for McMillan Dam, eventually settling on a rockfill design due to the perceived success of Avalon Dam. As the main storage reservoir for the PIIC system, Lake McMillan (the storage reservoir behind the dam) was designed to hold water that would be released to Lake Avalon, where it would then be diverted to the canals and their subsequent tributaries. At the time of its completion in Lake McMillan was touted as the largest artificial reservoir in the United States, and one of the largest in the world.

By it was reportedly the second-largest man-made reservoir in the nation and the fourth-largest dam in the world.29 Louis D. Blauvelt supervised the construction of McMillan Dam as its chief engineer. The completed dam had a maximum height of an average height of and an overall length of The rockfill dam had a crest width of Its upstream slope was faced with hand-laid stone. An outlet channel on the east side of the rockfill dam extends through solid limestone 35' below the crest of the dam; this channel served to discard water directly into the Pecos River below the dam.

Prior to the dam s completion, the Pecos River Valley suffered the first in long string of devastating natural disasters when torrential rain inundated the valley and raised the Pecos River to previously unknown levels, destroying Avalon Dam and damaging McMillan Dam.30 Timing of the flood coincided with the Panic of which caused financial uncertainty for many in the United States and made securing funds to repair the PIIC system difficult, if not impossible. Therefore, Hagerman funded the repairs himself at the cost of almost Within months of the flood, the firm Ward and Courtney began repairs to the irrigation system. Repairs were largely completed by early and water re-entered the canals just in time for the irrigation season.31 Another flood in further damaged McMillan Dam.

As McMillan Dam was still operational and because of the larger urgency of other improvements, repair work on McMillan Dam did not begin until Repairs included replacing the headgates, spillway and dike repairs and improvements, and constructing a new embankment along the eastern shore. This new embankment measured long and was designed to block off a large gypsum deposit that was believed to be responsible for much of the seepage that had been plaguing the dam since its original construction.32 In McMillan Dam was damaged during another flooding event that washed out portions of the embankments. Reclamation authorized repairs to the dam and provided a allocation to fund them during the winter of part of these repairs included raising the dam by about 3'.

Again in a flood caused more damage to McMillan Dam, this time exposing structural issues that led engineers to question its overall safety. Throughout and Reclamation engineers undertook extensive design studies aimed at providing additional spillway capacity. These studies included conducting test pits sunk into the dam, which revealed cracks and holes serious enough to require immediate attention. In response, Reclamation dug a trench 12' deep along the crest of the rockfill dam and filled it with puddle clay and gravel.33 29 Hufstetler and Johnson, Watering the Land, 40 41. 30 Hufstetler and Johnson, Watering the Land, 41 42. 31 Hufstetler and Johnson, Watering the Land, 43. 32 Hufstetler and Johnson, Watering the Land, 99.

33 Hufstetler and Johnson, Watering the Land, CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 8) Plans and cost estimates were completed at each of four potential spillway locations for low-head radial gates, high-head radial gates, roller gates, and a spillway siphon. Of the alternatives, the least expensive solution was to place a controlled spillway in or near the dam. A board of engineers finally met at the site in May to consider all the proposed alternatives. After test-borings in the foundation of the dam, the board was averse to any alternative that would dump water near the toe on the downstream side of the dam. The spillways finally constructed were more permanent than those proposed by the board.34 Spillway No.

1 is located approximately northwest of McMillan Dam. This spillway consists of a long concrete weir placed between concrete abutments. The weir rises only a few inches above the surrounding ground level, which in places was raised to the appropriate elevation with rock riprap. Water passing over the spillway enters a channel and discharges into the Pecos River about one-half mile below McMillan Dam. To protect the Atchison, Topeka, and Santa Fe's adjacent railroad bed, a long rock- filled dike with an earthfill face was constructed.

Engineers had to give special consideration to a portion of the lower end of the dike that was subject to high water velocities; here, Reclamation developed an innovative wire-bag riprap that had two advantages: the 6" mesh of the bags allowed the use of rock that was otherwise too small to be used in traditional riprapping, and labor was reduced by the ability to fill the bags directly from wagons.35 At Spillway No. 2, the wide mouth or crest of the spillway opens from the north, then swings around to discharge water in a west-southwesterly direction. The spillway was originally long, but a relocation of the Santa Fe Railway through the site in the reduced the spillway's length to The spillway has a concrete floor with concrete sidewalls rising 8' and sloping outward.

A wall through a portion of the center of the structure directs the flow of the water around the curve to the throat where the spillway straightens out.36 Work on the new McMillan Dam spillways began in the fall of under Reclamation supervision and was officially completed on May 26, Meanwhile, the Pecos River's erratic nature continued to manifest itself, with additional flooding in August followed by a substantial water shortage in The impact of the drought was further exacerbated by the rapidly decreasing storage capacity of McMillan Reservoir. This was a longstanding project concern, stemming largely from the substantial amount of silt the Pecos River annually deposited in the reservoir.

The problem had been recognized early in McMillan's history, and seemed destined to rapidly destroy the dam's effectiveness unless corrective measures were taken.37 By Reclamation estimated that some cubic yards of silt was deposited in McMillan Reservoir, and that within twenty years the reservoir would be virtually filled with silt. Several possible solutions to the problem were suggested and rejected: dredging the reservoir floor was dismissed as technologically impractical, and periodically raising the dam height would become progressively more expensive over the years. Therefore, the conclusion came to be that a 50,000-acre new site must be found that was free from the hazards of silting.

While potential sites had been identified, these plans failed to progress.38 34 Hufstetler and Johnson, Watering the Land, 35 Hufstetler and Johnson, Watering the Land, 36 Hufstetler and Johnson, Watering the Land, 37 Hufstetler and Johnson, Watering the Land, 38 Hufstetler and Johnson, Watering the Land, 123 CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 9) During the the CCC crews conducted general maintenance and repair work at McMillan Dam. The program's first major local project, during and involved the construction of a 2,000-foot extension to the east embankment at Lake McMillan. As with the reservoir's original east embankment, the extension was designed to remove small areas from the reservoir which were causing substantial water loss due to seepage.

The project involved the placement of some cubic yards of earth and cubic yards of rock at the site by hand. During the period CCC crews also constructed rock walls across the dam s outlet structure, along the road leading to the Gate Keeper s House, and around the Gate House.39 Flooding during May and June brought further attention to the structural needs and safety of the dam. At that time, water levels reportedly reached an unprecedented level, which caused leakage cracks to develop. These leaks raised more concerns that the entire dam might be endangered. A party of engineers from Reclamation s Denver office inspected McMillan Dam soon after the flood and recommended its immediate reconstruction.

The planned improvements included removing the top 11' and replacing it with compacted earth, raising the crest to a height of adding compacted earth fill to the dam's upstream slope, and widening its crest to The fill was topped with 3' of rock riprap. Additional work at site included pouring a concrete apron below the dam's headgates and clearing the channel below the headgates. The CCC began reconstructing McMillan Dam in November and most of the improvements were completed by the following spring.40 At that same time, the CCC was also working upstream to construct Fort Sumner Dam and Reservoir, to lessen the system s dependence on McMillan Dam.

The rehabilitated McMillan Dam and new Fort Sumner Dam kept the project running during World War II After the war ended, CID and Reclamation efforts returned to McMillan Reservoir s water loss. Although much of the loss resulted from seepage through the reservoir floor that Reclamation and the CID could not control, significant water loss was also attributed to the huge delta of silt that had accumulated at the reservoir s inlet. This area was overgrown with tamarisk, an invasive plant, which was absorbing great quantities of the reservoir s inflow through transpiration. To reduce this problem, Reclamation authorized the construction of a new river channel to bypass the stands of tamarisk.

The Reclamation construction team began building the new channel in October and completed it the following April In Congress approved construction of Brantley Dam to replace McMillan. During construction, Reclamation continued to dredge and maintain McMillan Reservoir, and even dredged a new channel in that would facilitate water flow to Brantley Dam.

(Hufstetler and Johnson The completion and opening of Brantley Dam and Reservoir in allowed for the final abandonment of McMillan Dam and Reservoir; plans to breach the structure began in and were executed in McMillan Dam and its associated resources remain extant but have not been in use since Brantley Dam became operational.42 39 Hufstetler and Johnson, Watering the Land, 40 Hufstetler and Johnson, Watering the Land, Hufstetler and Johnson, Carlsbad Irrigation District, 5. 41 Hufstetler and Johnson, Watering the Land, 42 Hufstetler and Johnson, Watering the Land, 148 CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 10) Part II. Structural/Design Information A. General Statement: 1.

Character: The McMillan Dam complex consists of three components: the Dam, Outlet Works, and Gate Keeper s House. The Outlet Works regulated water flow from the reservoir into the channel below. The Gate Keeper s House provided a residence for the person operating the gates. 2. Condition of Fabric: The McMillan Dam complex is generally in fair to poor condition. A portion of the earthfill dam has been breached mechanically. Extant concrete features of the Outlet Works show evidence of spalling. The roof of the Gate Keeper s House is missing corrugated- metal sheets, the porch is in disrepair with missing wood members, and all doors and windows have been removed. B. Description: McMillan Dam is an abandoned water-storage and water-control structure owned by Reclamation.

Completed in the dam and outlet structure were built at a location where limestone bluffs converge to narrow the width of the Pecos River Valley. The dam itself consists of a rockfill dam faced with a layer of impervious earth; it has a length of a maximum height of a crest width of and a bottom width of The headgate structure consists of five sliding metal gates housed in concrete through which water is discharged and emptied into an outlet channel measuring in length through solid limestone. The crest of the dam has a 13' deep trench filled with puddled clay mixed with gravel. When operational, two spillways protected the dam from seepage and erosion.

A 98'-long concrete apron on the downstream side of the Outlet Works was constructed to prevent the flow of water from undercutting the structure. The Outlet Works are located at the east end of the dam and regulated water flow from the reservoir into the channel below; oriented roughly east to west, the crest of the outlet structure serves as a deck for operating the metal slide gates. Random-cut stone walls with stepped buttresses on either side of its upstream face direct the flow of water into the gated conduits, and a poured-concrete apron immediately downstream of the discharge openings prevent scouring around the foundations.

The one-story Gate Keeper s House is also located at the east end of the dam and provided a residence for the person operating the gates; it displays a nod toward the National Folk style of architecture with its gable-front-and-wing form, L-shaped plan with a stone perimeter foundation, stone masonry walls, and cross-gable roof with a moderate pitch. C. Mechanicals: Water control was regulated by the vertical slide gates, which are components of the Outlet Works. Each slide gate is constructed of steel and is individually operated by wheel-handle cranks positioned above the gates on the north wall of the Outlet Works. When operational, water flowed through the CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No.

NM-4-A (Page 11) open, or partially open, gates into concrete conduits that conveyed the water into the outlet channel immediately downstream of the outlet structure. D. Site Information: McMillan Dam is in the Lower Pecos River Valley in southeastern New Mexico. The Lower Pecos River Valley is bounded to the east by the Llano Estacado and the Sacramento Mountains to the west. McMillan Dam is located within a mixed vegetation zone that includes creosote bush, tarbush, mesquite, acacia, and various species of cactus. The Burlington Northern Santa Fe Railway (formerly the Atchison, Topeka and Santa Fe Railroad) is a prominent linear resource situated west and south of the dam and its appurtenant works. CARLSBAD IRRIGATION DISTRICT, MCMILLAN DAM HAER No. NM-4-A (Page 12) Part III.

Sources of Information A. Primary

Source document Quoted word for word from HAER NM,8-CARL.V,1A-. Not written, edited or summarised by this site.

Bogener, Steve. Carlsbad Project. Albuquerque: U.S. Department of the Interior Bureau of Reclamation, Historic American Engineering Record (HAER), National Park Service, U.S. Department of the Interior. Carlsbad Irrigation District. HAER No. Hufstetler, Mark and Lon Johnson. Watering the Land: The Turbulent History of the Carlsbad Irrigation District. Denver, CO: National Park Service, Rocky Mountain Region, Division of National Preservation Programs, . Hufstetler, Mark and Lon Johnson. Carlsbad Irrigation District, National Register of Historic Places Registration Form. Washington, U.S. Department of the Interior, National Park Service, O Mack, Scott, Matt C. Bischoff, and Amanda Gronhovd.

The Canals of Carlsbad: Historical and Archaeological Evaluation of the Carlsbad Irrigation District Distribution System. Technical Report Tucson: Statistical Research, Inc., B. Likely Sources Not Yet Investigated: Reclamation provided access to known textual and non-textual records related to McMillan Dam. It is unlikely that there are other sources that would provide additional information.