This farm pond is part of the complex, low-relief watershed modeled by McCrone engineers using HydroCAD.

The site is primarily low-relief, poorly drained farmland including some wooded wetlands and several ponds. The parcel is divided by streams and contains many sumps. The stormwater management study point was identified at the intersection of Fork Branch (the parcel's boundary to the south) and one of its unnamed tributaries, which runs through the parcel. Although McCrone was not required to study Fork Branch itself, they were required to assess and manage water quality and quantity management at the study point. After meeting with Kent Conservation District (KCD), a pre-development drainage area was modeled in HydroCAD and the results were submitted. Using HydroCAD, McCrone modeled the farm fields, wooded areas, ditches, and sumps. HydroCAD's modeling flexibility allowed McCrone to effectively and efficiently manage and model numerous subcatchments, as well as the complex, low-relief tailwater conditions present on the site.

Civil 3D and Storm and Sanitary Analysis helped 4Site plan and size individual rain gardens.

One of 4Site's first projects with the software was an 85,000-square-foot commercial development project in Madison, Ala. The owner hoped to achieve LEED for Core and Shell certification on the project, which included two office buildings and associated site improvements. 4Site engineers designed the project using Civil 3D and then exported data from the Civil 3D model into Autodesk Storm and Sanitary Analysis software to analyze the stormwater network. During the design process, 4Site's engineers were able to model the entire project as a whole instead of in parts, adjust stormwater pipe sizes on the fly, see the impact that various storm events would have on the proposed system, and then make adjustments in real time. The analysis software handled flow calculations and hydraulic grade lines, and enabled the firm's engineers to update pipe sizes in a single step, without lengthy manual calculations.

The emergency main break results (left) show three major concern areas (dashed lines). The CIP map (right) shows the projects occurring during shutdown and highlights the two projects that should not happen at the same time as the shutdown.

Next, DC Water wanted to know what could potentially go wrong while the main was out of service that could jeopardize supplying water to customers. Hatch Mott MacDonald used WaterGEMS' criticality tool, which automatically removes one pipe at a time from the model, and then determines the impact of removing the pipe on providing customer demand at adequate pressures.

Hatch Mott MacDonald ran scenarios for 475 transmission main outages and 72 CIPs ongoing during the tunnel closure, including large valve replacement projects and water main renewal projects. The analysis identified 26 transmission main segments that resulted in more than 1 percent loss in demand and that could result in unacceptable service levels.

Michael Heigert, a design engineer at BG Consultants Inc., evaluates the Sewer NETwork within the Carlson Hydrology module

Initially, a closed-circuit television inspection of the entire collection system was performed by Mayer Specialty Services Inc. (according to Pipeline Assessment & Certification Program standards) to classify the size, material, and condition of the sewer main pipe. BG Consultants then surveyed the manhole locations using GPS, conducted manhole inspections, and then evaluated the inspection data utilizing IT Pipes software. Rehabilitation methods were then prioritized for approximately 375 manholes and 96,000 linear feet of sewer pipes ranging from 8 inches to 18 inches in diameter.

The Carlson Hydrology module was used by BG Consultants to efficiently build the entire sanitary sewer collection system. In Phase 1 of the project, approximately 32,000 linear feet of sewer main is scheduled for complete replacement through open trench construction. Tools such as "generate plan and profile sheets" were used to significantly expedite the creation of more than 55 plan and profile drawings, which will accurately define the parameters for this construction activity.

The utility has a conventional gravity flow interceptor system with sanitary sewer diameters ranging from 8 inches to 84 inches. The utility is responsible for operating and maintaining 14 lift stations and two off-line storage facilities. In general, sanitary sewer flows in the system are very responsive to rainfall. Peak flow rates at the wastewater treatment plant (WWTP) have produced peaking factors (peak flow divided by average daily flow) in excess of 10 during large wet weather events.

On Aug. 18-20, 2007, the city of Racine and surrounding areas received as much as 6 inches of rain on top of an already wetter-than-average month. This event produced safety site bypassing, basement backups, and excess flows at the WWTP. As a result of the system-wide basement backups and bypassing, the utility developed a system optimization plan to mitigate these issues.

System optimization was achieved by modeling the utility's interceptor system using the collection system model MIKE URBAN. Peak wet weather flow rates – dry weather flow plus inflow and infiltration (I/I) – were calibrated to match flows and levels at more than 30 locations from the Aug. 18-20, 2007, calibration event. The model uses the Rainfall Dependent Inflow and Infiltration (RDII) module to simulate fast (inflow), medium (rapid infiltration), and slow (interflow) I/I components. These components, when added together, make up the overall wet weather flow response for each sub-basin. Sub-basin time series flows are then routed through the sewer network to simulate hydraulic grade lines (HGLs) throughout the system.

Addition of the 2D module allowed a complete picture of the flooding and shortcomings of the current infrastructure.

The hydrology included 92 sub-basins employing the Green-Ampt infiltration methodology. The model was calibrated to three gages maintained by the project team during winter of 2010/2011. Many elements were added to the hydraulic model including all major irrigation canals, natural creeks, pipe conveyance, and updates to some of the existing model infrastructure. The updated 1D model is robust, complete, and appropriately represents the infrastructure currently in place.

However, a 1D schematization cannot accurately model flood water once it surcharges out of the 1D elements. When surcharging occurs, the model simulated this volume of water as lost at the point of surcharge and the overall model was inaccurate as it did not convey these flows overland. Numerous 1D locations surcharged within the model, therefore a 2D module was added to maintain model continuity and increase the model description. The 2D model revealed overland flow paths where the 1D system surcharged and connected downstream 1D elements with overland flows. The 2D model consists of 979,627 grid cells, each 10 feet by 10 feet, with 5.8 miles of large irrigation canals, 4.22 miles of creeks, and 5.44 miles of additional open channels all linked to the 2D module. This linkage of 1D and 2D allows flows in and out of the 1D system.

Source: CEnews.com