Aqualink -- Use of Three-Dimensional CAD in Filtration Plant Expansion

Many metropolitan need the United communities, to build States areas new are filtration throughout cities, facing and the fametropolitan areas throughout the United States are facing the need to b ild n w filtration facilities or to expand existing ones to cope with population growth. Two-dimensional computer-aided design (CAD) software has been used successfully for the design of such facilities and is now an accepted tool in the design of water treatment plants. However, recent advances in computer hardware and graphics systems have allowed three-dimensional CAD modeling software to open up another dimension in design. Although three-dimensional CAD technology is still in its infancy in terms of the production of design documents, the effective use of these models allows fast and sound decisions to be made regarding earthwork calculations, yard piping, and environmental impact studies. Such capabilities greatly enhance the ability of design engineers to conceive and evaluate effective and economical alternative design facility configurations. A recent design project for the expansion of a filtration plant was a joint effort between a large water agency and a private environmental consulting engineering company.* The joint project team was housed at the office of the private firm in order to maximize the team's efficiency. The scope of the design included expansion of the plant from 150 to 326 mgd. The major expansion features included two new conventional treatment modules, new chemical feed and storage facilities, a new 21-mil-gal finished-water reservoir with a floating cover and baffles, and six earthen washwater reclamation basins. The layout of the treatment plant expansion required a substantial amount of civil engineering work to calculate earthwork volumes. From the beginning of the predesign phase, the decision was made to utilize three-dimensional CAD, especially for civil design. It facilitated faster decisions about earthwork calculations and yard piping and visualization for environmental impact studies. Such three-dimensional visualization is not available with more conventional design methods. MicroStationt CAD software was used to prepare three-dimensional models of the site, process units, and buildings. The three-dimensional digital terrain data were input by digitizing existing contour drawings and by aerial photogrammetric techniques. The three-dimensional data from aerial surveying were supplied by subconsultants in a MicroStation-compatible file format.