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Washington (D.C.) Suburban Sanitary Commission (WSSC) Development Services Group reviews hydraulic plans for approximately 160 proposed development plans per year. This includes water and sewer system extensions as well as approximately 172 small-site utility plans (commercial private systems) that connect to the existing water and sewer network in two large Maryland counties.

Each system extension is hydraulically reviewed and mains are properly sized by WSSC hydraulic engineers during the hydraulic plan analysis process. In this process, engineers use hydraulic-grade benchmarks developed by the planning group within the existing system to analyze the proposed extensions and connections. These benchmarks are developed using system-wide modeling while considering the severest conditions in the system.

The WSSC hydraulic engineers determine the appropriate sizes for proposed mains while considering various scenarios that focus on system integrity and future needs to provide adequate fire flow and pressure to new developments. When the creation of a new pressure zone is sometimes required to serve a new development, the hydraulic reviewer interacts with the planning group that models the system-wide network to help with zone creations.

The project’s overall goal was to increase customer service levels by implementing a workflow process improvement. To meet this goal, the Development Services Group implemented Bentley’s WaterGEMS and SewerGEMS to decrease the turnaround time on reviews and keep pace with one of the most rapidly developing areas in the United States. The reviews were critical to the success of the projects as they serve as the primary planning mechanism for growth.

Increased review efficiency

Prior to using WaterGEMS and SewerGEMS, the Development Services Group completed hydraulic plan analyses with small-scale software developed in-house that was less advanced and less user-friendly. Using WaterGEMS and SewerGEMS, as well as group restructuring, the Development Services Group increased review efficiency through a standardized model between projects, improved quality assurance of reviews, and, over eight years, reduced review cycle times from an average of 73 days to 27 days for moderately complex projects, despite a two-fold increase in reviews.

The following examples illustrate review time improvements:

  • WaterGEMS’ and SewerGEMS’ scenario and alternative capabilities allow organized and systematic modeling so that other reviewers are able to use the model from where the original reviewer left off. And because model scenarios are created for each development phase of a project phase, each project can be reviewed for hydraulic integrity and adequacy easier and faster. This means that the developers who choose to move forward with a partial release of project phases can receive a quicker response from WSSC.
  • Environmental issues can also cause development engineers to re-consider alignments midway through the design process. Because hydraulic engineers have developed consistent models for each proposed development and system extension, the amendments to original alignments can be rapidly adjusted and re-analyzed. This means development engineers can make changes based on environmental issues more quickly and with less review time.
  • The Development Services Group can also be more responsive to system inspection changes during the construction process because they have access to the completed models.

On a larger scale, increased review efficiency is improving customer service and the overall delivery speed of an estimated 160 annual development projects from planning and design phases to construction-ready status. And because construction began sooner, revenues (through permit fees or new billing accounts) were collected sooner.

WaterGEMS model with various fire flow scenarios.

Reduced project delivery and operation costs

WaterGEMS reduced the time needed to size pipes accurately to meet WSSC’s system constraints and standards. This resulted in faster communication and turnaround to consultants and developers. As WSSC can process development reviews more quickly, the organization can expedite its revenue collection by allowing more customers to connect to the system sooner.

The use of WaterGEMS and SewerGEMS also has enabled the Development Services Group to spend less time modeling and analyzing a larger network of the system, to identify problem areas and potential outages, and to address them earlier during the review process. WSSC is implementing a new looping policy that should increase customer service and decrease operational costs, especially in areas that must be frequently taken out of service to complete pipeline inspections.

Safer water and sewer infrastructure

Adequate fire flow is essential for safety. The fire flow capability in WaterGEMS enabled reviewers to perform fire flow analysis for numerous locations throughout a large or small network used for a project in a single run. Reviewers could model multiple scenarios under various system outage conditions, including routine inspections of large-diameter prestressed concrete cylinder pipe mains, to determine the best solution that allows adequate fire protection.

Using SewerGEMS also enabled WSSC to analyze system issues in wastewater infrastructure during the development process. This resulted in a better quality hydraulic design and ultimately protected the environment from future sanitary sewer overflows in new development areas.

Workflows have been developed to help streamline collaboration between engineering, GIS, and consultants. For instance, simple GIS capabilities and the Model Builder functionality in WaterGEMS and SewerGEMS allowed reviewers to incorporate proposed pipelines within a development with existing pipelines in WSSC GIS container. WSSC improved workflow efficiency with more than an estimated 60 percent reduction in review cycle times for hydraulic analyses of development and system extensions.


Perrine Parrod is a senior product marketing manager for Bentley Systems Incorporated (www.bentley.com) for the hydraulics and hydrology product line. Parrod joined Bentley in 2004 through its acquisition of Haestad Methods.

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