Underground Systems: Hydraulic Design CONCRETE APPLICATIONS II CIMT 305 Underground Systems: Hydraulic Design 1. Drainage Structures Sanitary Structures Storm Sewers Culverts 2. Manning Equation Nomograph Roughness Coefficient, n 3.Hydrological Principles Precipitation Runoff Climatic Topographic C. Rational Method

1. Drainage Structures Sanitary Sewers The pipes in a sanitary sewer system must be Strong and durable to resist the abrasive and Corrosive properties of the wastewater. They must also be able to withstand stresses Caused by soil backfill material Reinforced Concrete Pipe (RCP) are suitable For larger sewer systems RCP is available in diameters up to about 20 ft. (6m) and in lengths up to 25 ft. (8m) RCP can suffer from crown corrosion due to hydrogen sulfide gas

1. Drainage Structures Sanitary Sewers Manholes are located over the pipe centerline under the following circumstances: When there is a change in pipe diameter Change in pipe slope Change in direction of pipe At all intersections At intervals not exceeding 400 ft. (150 m) Crown Corrosion H2S Septic Sewage Invert Concrete Pipe

1. Drainage Structures Sanitary Sewer Design 1. Slope of the sewer should follow the slope of the grade 2. Mannings Nomograph is used to determine the smallest standard pipe diameter that will carry the design flow. 3. For that diameter and slope, the velocity is checked. 4.Once the pipe diameter and slopes have been established , the invert elevations of the pipe can be determined and the proposed sewer can be drawn on the profile

1. Drainage Structures Sanitary Sewer A 120 –m reach of sewer is to be designed with a flow capacity of 100 L/s. The street elevation at the upper manhole is 90.00m and and at the lower manhole is 87.60 m, as shown. Determine an appropriate pipe diameter and slope for this reach, and establish the pipe invert elevations at the upper and lower manholes. Assume a minimum earth cover of 2m above the crown of the pipe. Ground

Chapter 3 -Hydrology 1. Rainfall Volume - acre-ft., hectares(ha) (V=Area x depth) Rainfall intensity - rate at which rain falls (in/hr. , mm/hr.) Recurrence Interval (N) years - the average time span between identical storms over a long period of time (i.e. 5 year storm- same as return period) Probability of occurence (1/N) - is the statistic of occurence in a single year

Chapter 3 -Hydrology 2. Surface Water A. Water Sheds Drainage Basin - Land which contributes runoff to a river or stream Confluence - the point at which two streams converge Tributary - streams that feed into a first-order stream Subbasin Tributary Drainage Basin Outlet