Integrating Sanitary Sewer System Automation with GIS

Introduction
Sanitary sewer system automation is a computer system to automate sewer management activities involving management and maintenance of public sewer systems, handling complaints of sewer line problems and processing customer accounts and billings. There are many commercial software systems that handle sanitary sewer system automation. However, most of these software products do not have any GIS (mapping) fi.mctions, or only provide certain linkage to an external GIS software for displaying maps. In the other words, GIS is not an integral component in these software systems.

Integrating GIS into sanitary sewer system automation will include GIS as part of the sanitary sewer management system, not only at system function level, but also at database design level. In this paper, a comprehensive sanitary sewer maintenance/management system, known as “Municipal Sewer Management System”, will be presented. The system integrates GIS as an integral component and provides functionality for public sewer system maintenance, private sewer system investigation, sewer system modeling, customer complaints and accounts processes.

Data Model
A data model is a high-level logic design of data interaction between system components. Most sewer management systems include at least three domains: public system, private system and customer. From the database design point-of-view, these are considered as three objects. An object can have attributes or properties, and relationships exist between objects. Figure 1 illustrates the conceptual data model for a sewer management system. Since GIS is an integral part of the system, the spatial entity (e.g., sewer line, manhole) is included as a property of an object in the data model.

Figure 1: Municipal Sewer Management System – Data Model
The Customer object is the user of the sewer system. It has attributes such as house address, owner’s name, account number, etc. The Customer owns the private system and pays bills to the sewer authority for using the sewer lines and for any maintenance activities related to the private system.

The Private System object is the sewer line within a house or a building. It has attributes such as house address, sewer line that it connects to, and the spatial entity of building sewer. Since the private system connects to the public sewer line (Public System), the private system can contribute to problems in the public sewer lines.

The Public System object is the public sewer lines (including manholes and laterals) maintained by the sewer authority. It includes three spatial entities: sewer line, manhole and lateral. Each entity has its own attributes such as type, size, etc. The three entities are related geographically; for example, a sewer segment has an upstream manhole and a downstream manhole.

The data model illustrated in Figure 1 defines the system components and data flow within a sewer management system. The data model provides a logic basis for the system design, which will be discussed in next section. Based on the data model, a database for municipal sewer management system was developed. The database has two parts: a GIS database and a sewer management database. The GIS database is a file-based database with graphic elements, while the sewer management database is a relational database that contains sewer management related information. The linkage between GIS and sewer management database is provided through common fields such as line_id, mh_id, etc.