Water Online the Magazine gives Water & Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.
Issue link: http://wateronline.epubxp.com/i/597858
In particular, karst voids within the Edwards formation provide a habitat for endangered cave-dwelling invertebrates, including six listed species of arachnids and insects. Strict controls on groundwater also exist in order to minimize any potential hydrological impacts to the karst system and the Balcones Canyonlands Preserve above, which has been set aside as a habitat for the Jollyville salamander and two species of protected rare birds. The temporary support design for the shafts is based on groundwater modeling, which showed there are dolomite zones within the Edwards formation that contain most of the permeability. But there is very little vertical connection between these zones, so the project team wanted to keep water that was found at its same elevation. The shafts therefore have a sealed lining, consisting of grouted liner plates, throughout the Edwards and Walnut formations. When a permeable zone was hit, the project team would also over-excavate and add a gravel ring, essentially behind the grouted ring, so that the water could travel around the shaft and continue to feed the same karst structures that it was feeding before. Once below the transition to the Glen Rose aquifer, the temporary rock support becomes bolts and wire mesh. There was intense coordination while the project team was sinking the shafts. The Environmental Commissioning Group was in the shaft 24 hours a day, and each time a void was found they were required to inspect it and ensure it was not a habitat for endangered species. In addition to the JTM, the project included the 92-acre water treat- ment plant site. In an effort to involve the community prior to clearing the site, MWH Constructors teamed with the city and local environ- mental groups to host two on-site native plant relocation and rescue efforts. The events were well attended by the community. MWH provided safety vests and conducted a safety orientation for volunteers. Upon completion of the WTP4 project, the administration build- ing, located at the water treatment plant, earned a silver-level LEED certification. The project team worked closely on a daily basis with the city of Austin and its environmental team to enhance and sustain their environmental responsibilities. Key Takeaways For Project Success The project team's focus on safety resulted in an unprecedented safety record for a project of this size and complexity. The project exceeded 1 million man-hours without a lost-time accident. Almost 3 million man-hours were logged at five locations, including work at Lake Travis and tunneling more than 7.5 miles with many crews working around the clock. Safety was emphasized and recognized with celebrations to honor milestones reached. In addition to construction safety, the treatment plant uses a new process that creates nonhazardous chlorine molecules on-site from a simple, safe chemical reaction process. No chlorine or ammonia will arrive on tanker trucks. The economic impact of this project is also a success. MWH hired 208 subcontractors and vendors and signed 385 subcontracts to work on the project. Eighty-eight percent of the vendors were local or regional. These contractors earned almost $285 million throughout the life of the project. WTP4 exceeded all the participation goals for minority and women-owned businesses; more than $63 million was earned by these businesses. Public outreach was also a critical success factor for the project. Austin's citizenry is civic-minded and protective of environmental resources and quality of life. City staff, the consultant, and MWH Constructors worked together to keep the community informed with public meetings and newsletters. The project team also main- tained a hotline that connected to a cellphone that was carried by a team member. This cellphone was answered 24 hours a day, seven days a week. The project team worked together through many challenges, including a tight budget and an environmentally sensitive site, to produce a water infrastructure that will contribute to Austin's water security for decades to come. n 20 wateronline.com n Water Innovations CONSTRUCTIONENGINEERING About The Authors Larry Laws is vice presi- dent and project director for MWH Constructors. Katy Perrino is the com- munications manager for MWH Constructors. Joseph Sesil is a con- struction manager with MWH Constructors. Concrete roofing rebar being installed at the 10-million-gallon clearwell structure Construction of the pump station building in Austin