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

2. 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)

3. 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

4. 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)

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

6. 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

7. 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

8. Questions?