EXECUTIVE SUMMARY

The City of West Jordan (City) has completed the 2019 Sanitary Sewer Master Plan Update (Plan). This Plan targeted the following items:

   •   Data Collection - Incorporate updated survey data for new developments.

   •   Update Existing Model - Update the InfoSWMM hydraulic model based on new survey data and include current sanitary sewer flows. Create a calibrated model to utilize in the future.

   •   Evaluate Buildout Scenario - Create a buildout scenario that will identify capacity issues for which the City will need to prepare.

   •   Capital Improvement Plan (CIP) - Prepare a CIP to be used by City staff for future planning purposes.

Previous master plans studied the sewer trunk lines in arterial roads, groundwater infiltration, and provided survey and model data for the major roads. The 2012 Master Plan provided comprehensive survey and modeling data for each manhole and pipe throughout the City, including individual neighborhoods. This Plan provides an updated existing model that includes the areas that have developed since 2012, an estimate of future growth based on the City's Land Use Plan, and the required sewer capacity to meet the per capita wastewater demand for this growth. The location and size of new pipelines were studied, modeled, and mapped, as were improvements to the existing sewer system under the CIP.

A Geographical Information System (GIS) based computer model (InfoSWMM) was used to evaluate the existing and future pipe collection systems. The computer model incorporates Global Positioning System (GPS) surveyed manhole and pipe elevation data collected by the City for each manhole and pipe in the City's sewer system. The current West Jordan population density from census data, and the current land use map were used to evaluate sewer usage per person for existing residential areas and to project future sewer use in undeveloped areas. Water use records from water meters were used to estimate existing commercial and industrial sewer usage. The existing sewer model was calibrated by comparing observed flows in several locations throughout the City with model output data for each location; model flows calibrated to within +/- 5% of the observed flows.

EXISTING SYSTEM EVALUATION

The results of the existing system evaluation indicate that most of the system is currently functioning within established capacity criteria. However, a few pipelines have reached or are approaching capacity. The areas requiring improvements are shown in Figure 6-1. The observed deficiencies are as follows:

   •   1300 West - The 1300 West 10-inch pipeline from 8600 South to 8200 South, then south of 9000 South is at capacity, due in large part to infiltration from groundwater into the sewer laterals, pipes, connections, and manholes.

   •   Grizzly Way - The 12-inch pipeline in Grizzly Way from Swift Water Way to 7800 South is at capacity because of the large area that has developed upstream of this location.

   •   Campus View Drive - The 8-inch and 10-inch diameter pipes in Campus View Drive are at capacity due mainly to the high-density residential development that is in the area.

There are various other isolated short segments of pipes (shown as red in Figure 6-1) throughout the system model that may be experiencing capacity problems or may have invert elevation or pipe size data that needs to be updated. These localized areas need to be investigated further with field monitoring to confirm if they are problem areas.

FUTURE SYSTEM EVALUATION

Generally, the location of the buildout collection pipelines was based on the previous modeling and master plan, which were in proposed roads from the Master Transportation Plan. Figure 6-2 shows proposed locations and sizes of future pipelines to serve the undeveloped areas.

Future wastewater demands were projected for buildout using the City's 2018 Land Use Map zoning designations (Figure 2-1), along with the most recent General Plan. The City of West Jordan Planning Department utilizes the estimates of residential dwelling unit densities and occupancy rates (people per household). While an approximate population number could be determined from this data, the buildout scenario used in this master plan update simply utilizes the densities, occupancy rates and the approved land use map to calculate future wastewater demands. Therefore, no specific population number is used within this update.

Buildout Capacity

There are some areas in the existing collection system that will not provide adequate capacity for the projected buildout flows as shown in Figure 6-2. The observed projected deficiencies in the collection system at buildout are as follows:

   •   9000 South/Old Bingham Highway - The main trunk line in 9000 South starting in Old Bingham Highway near 4600 West to Redwood Road varies in size and does not have adequate capacity. The 21-inch pipeline from Redwood Road to Jordan River Parkway is also approaching the 0.75 depth of flow to diameter of pipe (d/D) ratio level of service. In discussion with city staff, it was also decided to include this section of the collection system since there are going to be improvements done along 9000 South and it would be economical to complete this upsizing at that time.

   •   7800 South (West) - The 7800 South 15-inch pipeline between Mountain View Corridor and Highland Loops Road is over capacity.

   •   Wells Park Road - The pipes in Wells Park Road in the industrial park require additional capacity to provide the appropriate level of service as growth occurs.

   •   Jordan River Parkway - Approximately 1,300 feet of existing 24-inch pipeline under Jordan River Parkway between 9000 South and 8800 South does not have enough slope to carry future flows.

   •   Bagley Park Road - The pipe in Bagley Park Road in the industrial park is nearing capacity and is deteriorating due to age.

   •   7800 South (East) - The existing 36-inch pipeline in 7800 South from 1300 West to 1200 West needs to be replaced due to inadequate slopes that limit the capacity of the existing pipeline.

   •   7000 South - The 7000 South 12-inch and 15-inch pipelines from Bangerter Highway to 3200 West are nearing capacity and are deteriorating due to age.

There are other segments of pipes shown as red in Figure 6-2. These are identified as existing deficiencies in Figure 6-1, may have invert elevation or pipe size data that needs to be updated, or should be monitored as the City continues to grow.