Question
I wanna know how to calculate the highlighted values on last two pics. Could you plz detail the process of calculation for me? Thank you
A sewer collection design Design a sewer collection system incorporating flow rates, pipe sizes, pipe slopes and depths for the proposed residential development shown in the attached drawing. In your design locate suitable sewer alignments, manhole positions and other sewer appurtenances. The local approving authority accepts sewer alignments that service adjoining properties, i.e a common line that drains two adjacent properties. Salient spot reduced levels are shown in the table below. You may assume that intermediate levels may be derived by interpolation The development consists of residential allotments and a proposed primary school for 300 pupils. The reduced level at the school is 42.60 m. There are 4 equivalent persons (ep) to each residential allotment. The sewer size must be capable of carrying the maximum flow at the appropriate gradient and at depths not greater than three-quarters pipe diameter. Inflow/infiltration (II) may be derived from lengths of contributing pipes or catchment areas as appropriate. The following design data are used. ADWF, L/c.d VI, L/s.ha VI, m'/d.km 275 0.80 28 Primary school, ep/pupil 0.25 Use peaking factors shown in figure 6.7 of the study book and Manning's n of 0.013 Wastewater flow from the development will connect to a proposed sewer main at manhole M/10. The manhole M/10 also accepts upstream future flows from a catchment of 10 hectares and 250 ep, and drains towards M/II. Include calculations for a satisfactory sewer main and gradient between MI0 and M/II. The limiting upstream invert level at manhole MI0 for the upstream fiuture flows is 37.87 m RL. The manhole cover at M/I0 is 41.52 m RL. Show clearly the steps taken in your design with accompanying detail working of your calculations. Present your design in the format shown in table 6.7 of the study book.
Explanation / Answer
1. Let's talk about first two highlighted values 1.6643 and 0.2345. Here calculation is shown for line B/2 - D/2 and it is equal to 0.1141. And then it is written that B/2 - D/2 also accept upstream flow from C/1 - B/2 and B/1 - B/2. So next two values 1.6643 and 0.2345 are the PWWF values for line C/1 - B/2 and B/1 - B/2 respectively and can be calculated by the same process of line B/2 - D/2.
2. Now talk to about next highlighted value of equivalent persons (ep). Since there are 4 equivalent persons to each residential allotment to this is the number of 4* total number of residential allotment given in highlighted area to correspond sewer line.
I hope you will understand it. And if you want more clarification please reply and if you are clear with it please rate it as like. Thank You.
