R2021-09 Resolution Authorizing a Professional Engineering Services Agreement with Clark Dietz Inc. to Provide Final Design Services for the Brush College and Reas Bridge Lift Station and Forcemain City Project 2020-06

Home Browse Search

BRUSH COLLEGE ROAD SEWER STUDY City of Decatur • Phase I -flow from the existing two planned developments plus 25%of the existing undeveloped area. • Phase II -flow from the two planned developments plus 33%of the existing undeveloped area and providing sewer service to all the existing industrial and residential properties that do not currently have sewer service. • Phase III -the same as Phase II with all the identified Service Area developed. The acreages and estimated peak sewage design flow rates from these areas are summarized in Table 1. Table 1.Phased Design Flow Summary Addt'l Water Approx. Development Planned Service Existing Existing Plant Area Peak Design Phase Develop. Area Industrial Residential Admin (Acres) Flow(gpm) Phase 100% 25% - - - 118 680 Phase 11 100% 33% 100% 100% 100% 308 1,325 Phase 111 100% 100% 100% 100% 100% 550 2,830 Treatment and Tie-in Location Sanitary and industrial wastewater collected by the proposed new sewers will be directed to the City's existing collection system for conveyance to and treatment in the Sanitary District of Decatur's(SDD)existing wastewater treatment plant(WWTP). Based on discussions with the SDD,the WWTP has sufficient capacity to treat the expected flow rates. The capacity of the four existing sanitary sewers closest to the Service Area were reviewed to determine their feasibility as tie-in locations.Connecting to the Faries Park Pump Station was also assessed.The feasible and cost-effective sanitary sewer tie-in location is the 27th Street sewer at the intersection of Hubbard Avenue.This gravity sewer flows to the SDD's Damon Avenue Pump Station.The calculated available capacity in this sewer is approximately 1,325 gpm,which was the basis of the Phase II flow rate selection.Flows greater than 1,325 gpm exceed the 271h Street sewer capacity and will require either increasing the 27th Street gravity sewer size or pumping from the new Service Area all the way to the Damon Avenue Pump Station. The SDD feels that the Damon Avenue Pump Station has the capacity to accommodate the flows from the proposed Service Area. However,they are concerned about the capacity of the sewer system downstream of the Damon Avenue Pump Station.SDD has stated that this downstream sewer should be able to accommodate the Phase I flow from the Service Area but flows greater than this may require a capacity study of the downstream sewers. Infrastructure (Requirements The Service Area will require gravity sewers to collect sanitary and industrial wastewater. Due to the topography of the Service Area in relation to the City's existing gravity sewers,collected wastewater needs to be pumped to the existing collection system.Therefore,there will be three components to the new infrastructure:gravity sewers,a pump station,and a forcemain.The length and size of the various components depends both on the flows and discharge location(discussed above)and also on the Pump Station Location. Pump Station Location.Three potential pump station locations were evaluated for site constraints,forcemain length,gravity sewer requirements,and construction cost.The location at the intersection of Brush College Road and Reas Bridge Road (Figure 2)was determined to be the most feasible option because of its low initial cost and central location.The gravity sewer depth is minimized due to the central location and sewer is easily installed in the future along the surrounding main roads. Clark Dietz,Inc. 4 January 2021