162 | Page PEAK FACTOR CURVE FOR ESTIMATING PEAK FLOWS IN DESIGN OF SEWER NETWORKS: A CASE STUDY OF GADCHIROLI CITY Anushree A. Chandragade 1 and Rajesh Gupta 2 ¹Asst.Professor,Department of Civil Engineering, D.Y Patil College of Engineering Akurdi, (India) ² Professor, Department of Civil Engineering, Visvesvaraya National Institute of Technology, Nagpur (India) ABSTRACT Ratio of maximum to average flows, defined as a peak factor (PF), is observed to be dependent on contributory population. The Central Public Health and Environmental Engineering Organization (CPHEEO) recommended consideration of peak factors based on population range (CPHEEO Manual 1993). This type of consideration results in sudden reduction in PF as contributing population changes from one range to other. The sudden reduction in PF reduces the outgoing flows at a manhole and flow continuity at a manhole gets imbalanced. To overcome this problem of sudden reduction in PF, a new methodology is suggested in which peak factors are applied node wise to contributory population added at the manhole based on the total contributory population at outgoing sewer of that manhole. In the proposed methodology, thus the effective PF reduces continuously as the contributing population increases. The effective peak factors are compared with the PFs obtained by using both Babbitt’s as well as Harmon’s formula and observed to provide PFs on little higher side for lower flows. However, this difference diminishes as contributing population increases. Therefore, size and slope of sewers may not be much affected. Further, it is proposed to consider higher PFs than 3.0 as recommended by Haws (2013) for contributing population below 10000. The PFs of 4, 5 and 6 have been suggested for contributing population in range of 1000-10000, 300-1000, and below 300, respectively. This will avoid laying of sewer unnecessarily at higher gradient, or to make unnecessary arrangements of flushing when sewers are not laid at required gradient to achieve minimum velocity of 0.6 m/s at present peak flows. The proposed methodology of adopting PFs suits well to software SEWER 3.0 which allows consideration of PF node wise. The proposed methodology is applied to design the underground sewer network of the Gadchiroli Town. Salient features of the case study are presented. I INTRODUCTION Water after its domestic and industrial use converts to waste water. This waste water is required to be collected and treated before disposing safely to maintain hygiene and safeguard the health of citizen. A sewer network is to be designed to collect waste water from different locations in the city and transport it to the treatment plant. The Central Public Health and Environmental Engineering Organisation (CPHEEO) provides guidelines to