Agenda - Council - 06/26/2012 - Laserfiche WebLink

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peak flows is estimated. Typically flow variation between average and peak flows are between 2.5 for major trunk facilities and 4.0 for local lateral lines. Flow variation factors used in this study, as in past studies, were calculated using the empirical formula contained within the current edition of the 10-State "Standards for Wastewater Facilities". The flow variation formula is based on population. As the population increases, the flow variation factor decreases. This comprehensive plan is based on current land use planning. The plan continues the format of the 1991 plan by breaking down, in general, each 40-acre parcel in the City into developable and non -developable acres. To the extent possible the estimated number of units on undeveloped property comes directly from the 1991 plan. However, City staff has reviewed all of the development density assumptions used in this report to verify that they are consistent with current land use planning. Residential flow in previous plans was calculated based on 3.0 people per unit and 75 gallons per capita per day. This equates to 225 gallons per unit. Based on Chapter 4 of the City's 2030 Comprehensive Plan, the household size is expected to decrease to 2.87 people per house for years 2012 to 2020 and to 2.7 people per house for years 2020 to 2030. Sanitary sewer facilities will be sized to accommodate service areas at full post 2030 development and therefore a household size of 2.7 will be used for planning. This equates to 202.5 gallons per household unit per day. Commercial, industrial, office and mixed use land use flows are calculated based on 20 people per acre, which equates to 1,500 gallons per acre per day. Public designated land use flows are estimated at 750 gallons per acre per day and special flows are taken directly from the 2005 study. This report recommends that sewer sizing within the City of Ramsey continue to be based on ultimate flow projections. Previous Comprehensive Sanitary Sewer Studies anticipated that sewer treatment for the area north of Trott Brook would be treated at a future regional facility located within the North Trott Brook Service Area and also that all areas south of Trott Brook would ultimately develop to urban densities. The 2030 Comprehensive Plan shows the 2030 MUSA extending north of Trott Brook in the north central portion of the City. This expansion anticipates that significant areas south of Trott Brook would remain rural residential with no City of Ramsey Page 2-2 Comprehensive Sanitary Sewer Plan - 2012 Prepared by Bolton & Menk, Inc.