Schristian@lacsd.org

This paper demonstrates how GIS technology was used to address the impacts of growth on the regional sewer collection system in the Santa Clarita Valley. With a population doubling over the next 20 years, mostly from large master planned developments, use of traditional methods for determining impacts is nearly impossible. A much more dynamic and responsive system was necessary in order to plan for future needs of the system. Through a collaborative GIS effort with local jurisdictions and developers in the valley, GIS technology has proven to be an essential tool in developing a master sewer plan for this regional system.

The Santa Clarita Valley is located in the northwestern portion of Los Angeles County where Interstate 5 meets the Antelope Valley Freeway (14). The topography of the valley consists of rolling hills within the middle of the valley with the Santa Clara River flowing through the center to steep hillsides and canyons stretching to the north, south and east. Angeles National Forest contains much of the valley to the far north and south with the west bordering Ventura County and the east following the 14 to Acton and Antelope Valley.

Historically, the Santa Clarita Valley was the home of the Alliklik, or Tataviam Indians. In the 1700s, Gaspar de Portola claimed the Santa Clarita Valley for Spain, which facilitated the arrival of Spanish and other European colonists. Shortly thereafter, missionaries used the valley as a stop along the Camino Viejo, which ran along the western coast of California from Monterey to San Diego. In 1797, the San Fernando Mission was established, and the lands of the Santa Clarita Valley were ceded to the mission (Caughey, 1982).

The California Gold Rush in the 1840s also occurred in a portion of the Santa Clarita Valley as gold was discovered in Placerita Canyon in 1842. This brought on an influx of immigrants that brought urbanization to the valley. At the end of the Mexican-American War, the state of California was admitted into the union in 1850. In 1875 Henry Mayo Newhall purchased much of the western side of the valley. Much of these landholdings today are owned by the Newhall Land and Farming Company which comprise the majority of land currently being developed in the western portion of the valley.

Today, the Santa Clarita Valley is influenced by the heavily populated San Fernando Valley to the south, a bedroom community of the City of Los Angeles. Large master planned communities of mixed-use currently typify the Santa Clarita Valley with a large number of residents commuting out of the valley.

The County Sanitation Districts of Los Angeles County (Districts) are a confederation of 25 special districts that serve the wastewater treatment and solid waste management needs of over 5.4 million people in Los Angeles County. The Districts’ service area covers approximately 765 square miles and encompasses 78 cities as well as unincorporated territory within the county. Each District has a separate Board of Directors, consisting of the presiding officers of the local jurisdictions within the District, that work cooperatively under a Joint Administration Agreement (JAA). The JAA provides for a single, centralized administrative organization to coordinate the affairs of the Districts.

Collectively, the Districts own, operate, and maintain over 1,300 miles of main trunk sewers and 11 wastewater treatment plants with a total design capacity of 625.6 million gallons per day (mgd). The Districts currently receive, convey and treat an average of 540 mgd of wastewater. Approximately 37 percent of all treated effluent is suitable for reuse. The Districts also operate a solid waste management system that serves the needs of a large portion of Los Angeles County. This system includes three active sanitary landfills that accept approximately 14,000 tons per day of solid waste (about half of the solid waste produced in the county), two recycle centers, a transfer station, a recycle and transfer facility, and three gas-to-energy facilities. In addition, the Districts maintain two closed sanitary landfills and are partners in two refuse-to-energy facilities.

County Sanitation Districts Nos. 26 and 32 provide sewerage services to the Santa Clarita Valley. District No. 26 provides sewerage services for the eastern portion of the valley while District No. 32 provides sewerage services for the western portion of the valley. Districts Nos. 26 and 32 entered into an interim Joint Powers Agreement (JPA) in July 1984 in order to provide a more efficient means of wastewater conveyance and treatment. Under the JPA, the two districts jointly operate a regional system known as the Santa Clarita Valley Joint Sewerage System (SCVJSS). The SCVJSS is an interconnected network of approximately 3.6 miles of trunk sewers (District 26 Interceptor, District 32 Main and Relief Trunk Sewers), an activated sludge force main, and two water reclamation plants, the Saugus Water Reclamation Plant (SWRP) and the Valencia Water Reclamation Plant (VWRP). Districts Nos. 26 and 32 benefit under the JPA with joint financing, construction, operation, and maintenance of a regional wastewater system, and benefit from a large administration and support staff by being signatories to the JAA. Under the JPA, trunk sewers within the SCVJSS divert flow from the SWRP to the VWRP. This is because the SWRP is currently treating wastewater at its permitted capacity of 6.5 mgd, and cannot expand due to the lack of available land. Flows beyond the permitted capacity of the SWRP are conveyed to the VWRP, which currently treats 11.1 mgd for a combined valley flow of over 17.0 mgd.

Development within the Santa Clarita Valley is typified by large planned developments that include a variety of land use designations. A typical master-planned development includes a mix of residential and commercial uses ranging from 300 to 3,000 multi-family and single family dwellings surrounding commercial centers that support a variety of shopping, restaurant, and entertainment franchises. Within the past five years, over 86 master planned developments have been proposed and are in various stages of permitting, with 20 currently approved for construction. Assuming the typical build-out of each development occurs over a five year period from the time the Districts are given information on any development within its service area, an increase of 12.6 mgd could impact the current sewers and treatment facilities that service the valley. In addition, any planned relief of the conveyance or treatment systems in the valley also need five years to complete for treatment plant capacity and two to three years for sewer relief. Therefore, knowing the location of these developments and its impact to the sewers and treatment facilities that service them becomes critical.

Population growth within the Santa Clarita Valley has increased at an alarming rate within the past 20 years. The following table is a summary of historical and projected growth for the previous 20 years (to 1980), and projected into the next 10 years (2010).

In 1980, population statistics for the valley was approximately 69,000 people in an area comprised of four percent of the entire Los Angeles County, which had approximately 7.5 million people. In 1990, the population of Santa Clarita nearly doubled to 125,000 people while the county’s population increased from 7.5 million to 8.9 million. By the year 2010, the City of Santa Clarita estimates a valley wide population of 283,596 persons.

General plan information within the Santa Clarita Valley is maintained by the two jurisdictions, the City of Santa Clarita and Unincorporated County. It provides a roadmap for where growth will be allowed to occur within the valley through land use designations and enforcement. General plan information is often used to represent a picture of the ultimate growth pattern of the valley (also referred to as ultimate build-out). Sewers are typically designed for a shelf life from 50 to 100 years. Because of this, general plan information is typically used for the design of most sewers. However, jurisdictions routinely revise and adopt new general plans that change the scope of where development is allowed and where it is not. What complicates this further is the ability for designated land uses in a general plans to be amended by submitting a specific plan. In the case of Santa Clarita Valley, most developments occur in rural areas once designated as open space or vacant land, which typically requires a specific plan.

Another issue with general plan information that complicates the issue specific to the Santa Clarita Valley is that there are currently two jurisdictions, the City of Santa Clarita (City) and the Unincorporated County of Los Angeles (County) which enforce general plans in their perspective jurisdictions. However, general plans are vehicles for a community to express through code enforcement how that community takes shape. In this case, there are two general plans that do not necessarily have the same goals. A new cooperative effort between the City and the County has begun to create a new general plan for the entire valley, known as One-Valley-One-Voice. However adoption of this new document is far from being completed. Taking all of this in perspective, another approach for creating a long-term plan for sewers was necessary, due to the fluidity of general plan information.

Growth occurring at such a rapid rate also promotes a sense of mistrust between service providers and the people they serve. Will there be enough utility capacity such as water, sewer, and electricity? Are there enough schools, fire response, and police to manage such a large influx of people into an area in such a short amount of time? It is crucial that communication between service providers and the community they serve be enhanced, and encompass the total picture of development within the valley and the plans set in place to accommodate growth that has been approved of.

In the case of creating a long-term plan for necessary sewer relief, it is clear that conventional wisdom of relying on general plan information won't work. GIS offers solutions to help develop a dynamic plan which otherwise would be published with little confidence in its conclusions.

The first step in producing a more dynamic planning process using GIS is assembling usable data. Information such as location of local and regional sewers and treatment facilities were built, with drainage areas for each sewer being defined by digital terrain models, jurisdictional boundaries, and other topological features. General plan information for both jurisdictions was assembled or obtained to cover the entire valley. Other information such as location of sewer permits issued, trends of water use, population statistics, proposed developments, and aerial imagery are also apart of the system and are used in various ways to track the impacts of growth.

GIS technology was used to formulate drainage boundaries for treatment plants as well as sewers that the Districts own and operate. Because of the steep terrain in the Santa Clarita Valley as you move away from the Santa Clara River, using a digital elevation model for delineating boundaries became very useful. This data, which was obtained from United States Geological Survey, in combination with Angeles National Park Boundaries were used to determine boundaries for the sewers and treatment plants within the valley. Local sewer information as well as other topological features was also used in formulating boundaries.

Intersecting general plan information that was assembled for the entire valley allows for quick calculations of wastewater flow for each individual length of sewer as well as treatment facilities. As discussed earlier, general plan information in this case is highly suspect, however, GIS does allow for quick and accurate calculations of flow by using standardized coefficients of flow for land use categories. Initial calculations for flow were derived using this method which also allows for quick and easy updates of flow numbers as general plan information is changed.

A key approach for implementing a more dynamic process is to migrate Development Monitoring System (DMS) data into the GIS system. The Districts receive development information in the early planning stages as a responsible agency under California Environmental Quality Act (CEQA). This allows development data to be cataloged and processed into the current DMS. Included in this data is information on how many single family, and multi family units are proposed along with square footage of commercial and industrial developments. Based on this information, an estimation of wastewater generated by the proposal is also given along with the current capacity of the sewer and treatment plant that will serve the development. By migrating this data into GIS as polygons of development, we are able to monitor the progress of these developments using growth development indicators such as sewer connection data and aerial photography. Using this information in GIS also allows for easier use with sewer and treatment plant drainage areas, being able to sum up cumulative flows easily.

Master planned developments can be considered as pockets of as-built conditions. Because of the nature of these developments (maximizing building space on available lands) it is unlikely that any new development would occur in the confines of a completed master planned development. In addition, developments seeking a change in the designated land use established in a general plan are required to submit a specific plan, which subsequently amends the general plan. Because of this, master planned development data is a good resource in augmenting existing general plan information for a more accurate depiction of how the valley will build out. Without the ability of GIS in combining data spatially, this would be a very large task.

Population statistics are another approach for determining a planning horizon somewhere between ultimate build-out and what can be determined through development data. Population projections are adopted by a number of agencies within the Santa Clarita valley, which take into account economic forecasts as well as general plan information to establish a projection usually no more than 20 years into the future. This type of information is easily assimilated into a GIS system, as it is usually desegregated by census tracts, information widely available with most GIS map bases. Population projections can also be equated to flow using a per capita generation rate. This information is useful to look at the consistency of other flow projections derived by development data or general plan information.

One of the most important by-products of developing this plan using GIS is an over-all enhancement of communication with the people the Districts provide service to. Good working relationships have been established with the City of Santa Clarita (City) who has a mature GIS system in place and has migrated much of the City’s data to that platform. This allows the Districts to dynamically share information with the City over an established ftp site. In turn, the Districts communicate cumulative flow data to the City providing them a level of confidence that the current sewerage system can accommodate the flow. A joint effort in maintaining development data with the City and the County allows for any developments that somehow fail to notify the Districts through the CEQA process to also be accounted for. This joint cooperative effort has led to many other opportunities to share information with the City that indirectly helps the planning process.

In conclusion, GIS technology has made a seemingly impossible situation possible. With the ability to interact with differing data spatially adds an entire dimension to the planning process. Working through cooperative relationships with the City and County have added an additional depth and meaning to any planning document as it directly addresses the needs and concerns of the community that the Districts serve.