YS-INF-ESCP-02

 WET SEDIMENT BASIN DESIGN

Problem

Design a wet sediment basin for a 3 ha site located nearby Gunung Brinchang, Pahang. The land surface is categorized as bare soil, where the overland flow is 79m in length with the slope of 0.1%. The site runoff potential is found very high with design storm event magnitude of 50mm.

Solution

1. Determine the Horton's roughness based on land surface by referring to Table 2.2, MSMA 2.
2. Calculate overland flow time using equation stated in Table 2.1, MSMA 2.
3. Determine surface area and volume of basin required per ha of land by referring to Table 12.19, MSMA 2.
4. Calculate the actual surface area and volume of basin required.
5. Determine the side slope for basin, complying with requirement as stated in Table 12.17, MSMA 2.
6. Determine the volume of settling zone required, which equals to half of the total basin volume, as per Table 12.17, MSMA 2.
7. Determine the depth of settling zone provided, subject to minimum of 0.6m.
8. Determine the average width and length of basin settling zone, where the resultant length : depth ratio should not be greater than 200 and length : width ratio should not be less than 2 (Table 12.17, MSMA 2).
9. Determine the depth of storage zone so that the volume of storage zone equals to half of the total basin volume, as stated in Table 12.17, MSMA 2.
10. Based on nearby rainfall gauge station (Table 2.B1, MSMA 2) and design ARI of 10 years (Table 12.17, MSMA 2), calculate the runoff discharge (Equation 2.2 & Table 2.5 & Equation 2.3, MSMA 2).
11. Determine the dimension and head of riser, then calculate the flow capacity of riser using Equation 2.6, MSMA 2.
12. Determine the dimension of spillway, then calculate the flow capacity of spillway using Table 2.7 & Equation 2.10, MSMA 2.