Final Draft - Wastewater Collection System Capacity Analysis Apprendix A April, 1999

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Final Report City of Paris, Texas Wastewater Collection System Capacity Analysis The Storm Event graph shows in greater detail the nature of the flows during the viewed event. It includes all of the above parameters and additionally shows what portions of the flows arise within that basin. This is again a very good way to determine the nature of the dominant defects within the system. System Data The entire collection system was inspected during the physical inspection phase of the program. This resulted in the accumulation of mapping information that was used to update existing collection system maps. Additionally several techniques were employed to locate and identify defects within the system. All of this information was captured into digital maps and was used as the basis of the collection system model. Details of the defects located are presented in the other portions of this report. GPS Program As a portion of the data collection, a limited GPS survey was performed. This resulted in the establishment of elevations for approximately 270 manholes in the system. Of these 240 were matched and based on these elevations, grade lines were established where possible. 30 GPS points were not used as there was no near matching XY coordinates. It was assumed that the enor in XY would likely be observed in the Z elevation as well. Assumptions In all endeavors of this magnitude, certain assumptions must be made when data is unavailable or of questionable origin. In these areas a conservative approach has been taken to assure that the model represents the system under a"worst-case" scenario. It is important to note that as the system data is updated and verified this can be incorporated into the system model and its overall impacts assessed. A common assumption or estimate of this type is in the roughness of the pipe. The actual ability to measure this roughness may be possible in university laboratories but is practically impossible in the field. The roughness coefficient that is employed tends to generate a capacity number that is slightly less than would be measured in the laboratory setting. This results in a conservative estimate of the flow. Another example of this type of assumption would be in the determination of pipe slope. Pipe slope is a very important parameter in the determination of the hydraulic capacity. To acquire this information, field measurements are made which include the measurement of the bottom of the pipe from the rim of the manhole. This is a difficult task to accomplish in the field. A reasonable assumption (in the absence of field data) would be that the pipe was laid at minimum slope. The capacity that would be calculated would be the minimum that would be accepted by the local authority. The underlying 13