Water Drainage System Harris County, TX Hydro point llc. (Team 1) – landon allen, chadi kanan, Catherine Lundberg, Michael rauschuber, Fernando torres

Introduction and Problem Design Pipes Junctions (two inlets per junction) Gravity System Water Drainage System Construct a storm sewer design Accommodate 2 year, 3 hour storm design Prevent impacts downstream Area Crosby, Texas (Harris County) Gum Gully Creek (Outfall)

Project Area Land Area: 48.85 acres, north west of Gum Gulley Creek Enclosed by Jolly Boat Dr., Broken Back Dr., and Golf Club Dr. Elevations ranging from: 14’ (water surface of Gum Gulley) to 48’ (north west corner of area) above mean sea level. Soil CH-fat clay, hydrologic soil group D – clays that are highly impermeable (Web Soil Survey) Water shed Undeveloped grassland with trees that is used for agriculture or as a natural habitat Large portions are undeveloped and unfarmed forest Outfall at Gum Gulley Creek

Hydraulics Curb on grade inlets (15’ and 20’) Capacity and area that matches capacity Prevent erosion No detention basin needed Meet velocity requirements (3-8 fps) Outfall elevation EPA SWMM 5 Junction Placement Rain Gage – 2 year design storm, 3 hour SCS Type III hyetograph Backfill – Alter outlet offset to lower velocities and maintain at least minimum slopes Examine area through 18:30 to examine all flow *Since a detention basin is not suggested bc little difference in volume between pre and post development hydrographs. Make the outfall elevation similar to the creek’s water surface elevation (14’ with land elevation [bank?] at 19’) *Junctions placed according to inlet capacity size (area of 4 acres for 20 ft curb on grade inlets [12], and then 2.4 acres for 15 ft curb on grade inlets [2]) – two inlets per junction and then added more to keep pipes inside public road ROWs *Rain gage – make 24 SCS type III empirical hyetograph and pick largest 3 hours (11:00-14:00)

Hydraulics Velocity: Maximum at Conduit 31 (7.72 fps) Minimum at Conduit 26 (3.11 fps) Slope: Minimum at Conduit 13 of 0.0016 (0.0013 required) Backfill Maximum at Junction 24 of 10.5ft Minimum at Junction 1 of 3ft 21 junctions 21 conduits

Cost Clearing/ Grubbing of land is roughly 25% of total cost Materials are most substantial part of cost Materials include concrete piping, grade inlets, manholes, and junction boxes Grade inlets consist of 5’ (Type C-1) & 10’ inlets (Type C-2A) combined to reach optimal length needed Engineering -15% Contingency -15% - Based on current bid prices

Summary and Conclusion Purpose: Safely carry storm water from all areas of the subdivision to the proposed outfall at Gum Gulley Creek (southeast of the area) while preventing erosion at the outfall or downstream. 7 drainage areas contributing to 7 junctions (2 inlets per junction) 12-20ft inlets (drainage areas equal to ~ 4.0 acres); 2-15ft inlets (drainage areas equal to or slightly greater than 2.4 acres) Safe velocities, slopes, and backfill due to Harris County requirements (3-8ft/s, 0.13%, 3ft) Pipe size increases based on flow capacity coming through inlets 18” – 2881 linear feet 24” – 1265 linear feet 30” – 847 linear feet Table 1. Alloted Drainage Area per Inlet Capacity  Inlet Size (ft) Inlet Capacity Q (cfs) C i (in/hr) tc (min) A (acres) Q (cfs) 10 3.5 0.4 6.76 1.29 15 6.5 2.40 20 11 4.07

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