Application of GIS in the design of new Wastewater Systems Kenny Johnson CVEN 689: Applications of GIS Texas A&M University Public Wks/Infrastructure

Overview Some of the most important services we use everyday are located just beneath us. The operation of today’s wastewater systems require ongoing planning, maintenance, and management. “Collectors” consist of the smaller diameter pipes from residencies and businesses. Wastewater enters the system by these “collectors”. The need for new pipelines arises as a city grows.

Overview New land development has led urban designers new means of sewer systems planning Using existing structures will optimize any design Surrounding environment will control design

Based on:  Topography: requires lift station for uphill movement of wastewater  Land use: Existing structures limit alternatives  Soil Properties: Some soils more difficult for construction  Constructability Issues: Accessibility Issues

Objective Location: College Station Automated design process that seeks the most feasible location on the existing pipeline to tie in to Standard ArcView tools required Elevation, land use, and existing sewerlines data required

Methodology – First Trial Land Use evaluated on cost  vacant lot = small “cost” Elevation evaluated on cost  large elevation = large “cost” Weighted Overlay tool used to combine Land Use and Elevation Cost Weighted Allocation created to find most feasible source (existing pipeline)

Land Use Converted to Raster Pre-logic VBA Script Code If [LAND_USE] = "Vacant" Then num = 1 ElseIf [LAND_USE] ="Parkland, Greenways" Then num=2 ElseIf [LAND_USE] ="Civic/Local Government" Then num=7 ElseIf [LAND_USE] ="Rural" Then num=1 Else num=9 End If CostValue=num Features to Raster conversion based on the CostValue field. Reclassify and make No Data = 6 since this is the streets.

Land Use + Elevation = Cost + = Cost Weighted Allocation  =

Cost-Weighted Allocation

Limitations Elevation not directly proportional to cost values Only small integer values (1-9) can be inputed into Weighted Overlay Only small integer values (1-9) are outputed from Weighted Overlay The weighted percentage is limited to a total of 100% Only a small portion of the map could be analyzed by elevation cost due to the large array of values

Methodology – Final Approach 1.Create point of interest 2.Create an aspect of elevation 3.Raster Calculator used for correlation between point direction and aspect of elevation 4.Resulting Raster will consist of allowable straight line directions towards existing pipeline 5.As before, land use values will be given to a land use raster 6.Raster Calculator to create a weighted cost raster 7.As before, weighted cost allocation created

Point of interest & aspect of elevation created

Straight line distance to point of interest

Correlation Equation: Elevation Aspect + 90 > Point Direction & Elevation Aspect - 90 < Point Direction

Calculated Results

Create Cost Raster Flow Direction + 5 x Land Use = Cost Raster ) = + (5 x

Final Allocation

Another Example

Result

Conclusion Procedure utilizes GIS capabilities for the planning of wastewater systems Important for achieving the most economical design Process could be more automated with the use of Visual Basic A more detailed design could take into account pipe diameter, usage, accessibility, and soil type

THE END Questions?