C+S April 2020 Vol. 6 Issue 4 (web)

water + stormwater

For more than three centuries, the verdant South Valley of Albuquer- que has been a bountiful farming community with irrigation ditches leading to and from the iconic Rio Grande River. While these ditches are a lifeline to the farming and ranching residents of the area, these ditches can be dangerous. According to the Albuquerque Metropoli- tan Arroyo Flood Control Authority (AMAFCA), some ditches have deadly undertows and many contain rocks, glass, barbed wire and even dead animals. The months of March through October can especially perilous because the ditches are usually filled with water. Undertows can happen at any time of the year; however, in Spring the water is cold enough to cause shock and hypothermia. These ditches can be prone to overflow and rushing water due to rain or snow melt rushing down from the mountains causing flash-floods or the sudden downpours dur- ing the state’s monsoon season. Flooded ditches can lead to drowning – New Mexico’s number one natural disaster – within minutes. It came as no surprise that over time, a practical solution was needed to keep water in the South Valley running safely and smoothly. “There was a lot of flooding in the valley floor because of limited outlets from the inside of levees into the Rio Grande,” said AMAFCADevelopment Review Engineer Nicole Friedt, PE. “The dams were being used to drain irrigation facilities and that’s not their purpose. We needed to provide appropriate outlets.” In its quest to create a solution to the irrigation and storm drainage issues, AMAFCA enlisted the expertise of local engineering and ar- chitectural firm Wilson & Company. “If there is a huge storm and the irrigation ditches are full of stormwater, the water can’t get out of the dam,” said Wilson & Company’s Design Engineer Tyler Ashton, PE, PMP, CFM. “Back-to-back storms could cause a big problem.” To devise a design solution, engineers searched for an easy and inex- pensive alternative for project placement. “We reviewed three main corridors and chose the one with the least amount of existing utilities,” Ashton said. “If we ran a pipe down a road to the east, we would have had 202 conflicts. Another road had 69 conflicts. The most economi- cal corridor was the Gun Club Lateral because it only presented 19 conflicts in the three-mile stretch. Its terrain is very flat. Fortunately, the site is also raised, which allows gravity to create positive flow.” The first phase of the Black Mesa Project was constructed in 2009 by the U.S. Army Corps of Engineers, with a cost shared by Bernalillo County and AMAFCA. AMAFCA constructed the next phase – known as Phase I.a – in 2014 as well as Phase II in early 2019. Estimated to cost $7.6 million, construction of Phase III and Phase IV, began in November 2019 and is projected to finish by March 2020. Black Mesa Project Lowers Flooding Risk in Albuquerque’s South Valley By Kimberly Paggioli

The finished project will connect the drainage from three dams – the Don Felipe Dam, the Raymac Dam, and the McCoy Dam – into one pipe manifold and drain the water to the Rio Grande River. “Three individual dams and three separate pipes would have been very expensive,” said AMAFCA Executive Engineer Jerry Lovato, PE. “By minimizing how much pipe we put into the ground, this project will save money. Once the dams are connected, the pipe is pressurized.” When selecting materials, AMAFCA chose Hobas centrifugally-cast, glass-fiber-reinforced, polymer mortar 42-inch and 36-inch pipes with tee bases and 30” flanged tops to serve as irrigation piping for agriculture. One of the main reasons for using Hobas pipe is its pressure rating, Lovato said. “Normally we would use reinforced concrete pipe, but it doesn’t have the required 21.6 PSI pressure rating,” he explained. “Even though that may be considered a low pressure rating for Hobas, it’s high for us.” The construction timetable is critical. “AMAFCA shares the right-of- way with the Middle Rio Grande Conservancy District, which supplies irrigation water through open ditches to farmers,” Lovato said. “Con- struction can only take place in a four-month time window – March 1


april 2020


Made with FlippingBook Annual report