Washington Street West watershed - City of Champaign

More documents

Recommendations

Info

Draft ReportWest Washington Street Watershed Master Plan• Maintain the existing poorly defined surface flow (flood routing) along the WestWashington Street corridor for wet weather events or develop an alternative surfaceflood routing drainage path• Reduce the likelihood of yard and excessive street flooding along the West WashingtonStreet corridor for storm events smaller than the 50-year storm event• Where possible, incorporate water quality objectives with storm sewer improvementprojects defined in the local improvement scenariosThe proposed alternative solutions address each of these objectives through varying means andeffectiveness, but all are based on the above objectives. The alternative solutions include severaldozen options that will be discussed in the following sections. These solutions will contain shortterm implementation strategies that can be implemented quickly and provide preliminary benefits.A section will follow that combines several alternatives into a long term solutions that requirephases to attain increased stormwater runoff protection. Early, short term, phases should be partof the final solution and presented combination scenarios will not include temporary componentsof a final solution.6.3 PROPOSED SOLUTIONSThe proposed solutions were developed using the stated goals and city standards for sewer androadway design. The stormwater detention structures were sized to detain the 100-year, 2-hourstorm event. Stormwater detention structures are normally designed for the 50 or 100-year, 24-hour storm event; however, the modeled high water level for the 24-hour storm events were lowerthan the 2-hour event and during this planning level study the most conservative hydraulicconditions are used in the hydraulic analysis. Traditional storm sewer design tends to design forthe 10-year flow event, which is the target design flow for most of the presented sewerimprovement alternatives. When the additional flooding along the West Washington Streetcorridor is considered in the sewer design, a complex storm water drainage problem emerges witha multiple phase solution the most practical method to implement recommended solutions.Based on the watershed land use and existing sewer configuration, localized flooding throughoutthe watershed for the 100-year, 2-hour event is practically unavoidable. The proposed solutionsmodels were developed to simulate conveyance paths for events up to the 100-year, 2-hour eventso that each alternative could approximate the resultant flood routing for these large events. Atable summarizing each alternative can be found in Appendix B.6.3.1 Stormwater DetentionThe West Washington Street watershed is a fully developed watershed that lacks anyofficial stormwater detention structures. These structures are designed to limit the sewersurcharging, reduce local flooding, lower discharge rates to the receiving waterways andimprove the hydraulic conditions throughout the storm sewer system. Stormwaterdetention structures are typically required in new developments, when drainage plans canidentify flooding areas and natural low spots that would be better used for stormwatermanagement rather than buildings or roadways. In many instances, constructingstormwater detention structures within older neighborhoods can still provide local reliefto flooding and sewer issues, while improving the flow conditions in the receivingwaterway.September 20096-2Clark Dietz, Inc.
Draft ReportWest Washington Street Watershed Master PlanFigure 6-1Detention PondsThe following sections will present the stormwater detention alternatives developed forthe West Washington Street watershed. The blue areas shown in Figure 6-1 display thepotential detention pond locations that will be discussed in this section. This section willbe subdivided into five categories:• West Washington Street Trunk Sewer Stormwater Detention Ponds• North McKinley Avenue Trunk Sewer Stormwater Detention Ponds• North Edwin Street Trunk Sewer Stormwater Detention Ponds• Regional Stormwater Detention Ponds• Other Stormwater Detention OptionsEach potential pond site will be presented with a figure containing the approximatefootprint of the pond, a table with basic design information, and a short discussion. Thebasic design parameters were used for modeling purposes and are not intended for use ina final design. The maximum detention volume assumes a vertical side wall design, withthe effective pond volume determined by assuming 3:1 side slopes and at least a foot offreeboard to maximize capacity and safety.The hydraulics of the ponds was modeled so that both the inlet and outlet sewers will actas inlet sewers initially and once the storm has subsided, both sewers act as the outlet byallowing flow out of the pond. It is possible to alter this operation through flap gates andother flow restrictions that would be best determined during design.September 20096-3Clark Dietz, Inc.
Page 1 and 2: West Washington StreetWatershed Mas
Page 10 and 11: Draft ReportWest Washington Street
Page 15: Draft ReportWest Washington Street
Page 42 and 43: PondSize(acres)PondDepth(feet)Table
Page 49 and 50: PondSize(acres)PondDepth(feet)Table
Page 53: Draft ReportWest Washington Street
Page 72 and 73: 6.3.5.5 Alloy Casting Ponds and Chu
Page 80 and 81: Table 7-2Combination Alternative Co

Washington Street West watershed - City of Champaign

Create successful ePaper yourself

Delete template?

Save as template?