Conceptual Servicing Report (Attachment 5)

CONCEPTUAL SERVICING REPORT

To: Town of View Royal Engineering Department From: Nathan Dunlop, P.Eng., Project Engineer, McElhanney Ltd. (Victoria office) Re: 339 Island Highway, View Royal, BC Conceptual Servicing Report Date: February 23, 2023

1. INTRODUCTION

The proposed development is located at 339, 341 and 345 Island Highway in the Town of View Royal (TVR), BC. The site is generally south of the Island Highway, east of Prince Robert Drive and west of the View Royal Public Safety Building (333 Island Highway).

This Conceptual Servicing Report is submitted in support of the Rezoning Application. This report will provide information on the existing and proposed storm, sanitary and water infrastructure for the proposed development.

2. EXISTING CONDITIONS

2.1. ISLAND HIGHWAY

The following infrastructure exists within the TVR road right-of-way:

• Storm:
  • 300 millimetre (mm) diameter (dia) main of unknown material
• Sanitary:
  • 900 mm dia Polyvinyl Chloride (PVC) DR41 gravity main
  • 200 mm dia Polyvinyl Chloride (PVC) gravity main
• Water:
  • 900 mm dia Steel (ST) main (CRD Main No. 2)
  • 200 mm dia Asbestos Cement (AC) main

2.2. PRINCE ROBERT DRIVE

• Storm:
  • 150 mm dia PVC gravity main (west side of road)
  • 300 mm dia PVC culvert (east side of road, crossing into private property)
• Sanitary:
  • 200 mm dia PVC gravity main
• Water:
  • 200 mm dia DI main

3. DESIGN CRITERIA AND ASSUMPTIONS

3.1. STORM

• Design Criteria:
  • Subdivision and Development Servicing Bylaw No. 985 – Section 5.21 – On-site Stormwater Management System
  • Provide post-development runoff equal to or less than pre-development runoff, up to a 1 in 10 year rainfall event
  • Flows above the 1 in 10 year rainfall event will flow overland
• Assumptions:
  • Victoria-Gonzales IDF curve used in the calculation of flows

3.2. SANITARY

• Design Criteria:
  • Subdivision and Development Servicing Bylaw No. 985 – Section 5.19 – Sanitary Sewage System
  • Sewage flows will be based on per capita flow rates provided in the Master Municipal Construction Documents (MMCD) Design Guidelines 2014 Section 3.2
    • Average daily dry weather flows (ADWF) for new fully water metered systems = 240 litres per day per capita
  • Peak flow rate is calculated by applying a peaking factor (Harmon) to the ADWF.
• Assumptions:
  • The occupancy load is based on the number of residential units as proposed in the Rezoning documents.

3.3. WATER

• Design Criteria:
  • Fire Flows in accordance with the Fire Underwriters Survey (FUS) with 140 kilo Pascals (kPa) or 20 pounds per square inch (psi) of residual pressure.
  • Domestic Flows: meter sizing will be based on the American Water Works Association (AWWA) M22 calculation.
• Assumptions:
  • The FUS calculation and the AWWA M22 calculations will be based on the building configuration and occupancy load as proposed in the Rezoning Application.

4. PROPOSED FLOWS AND LOADS

4.1. STORM

Storm water from within the development lot will be collected via roof and area drains and connected to the onsite storm water management (SWM) system. The SWM system will consist of onsite conveyance mains, storm water storage (rain gardens) and a flow control manhole. Storm water will be discharged from the site through an orifice-controlled outlet into the existing 300 mm dia storm main along Island Highway. Due to potential conflict with CRD Water Main #2, the storm service for this development may require installation of a new storm main along Island Highway (to be confirmed during detailed design).

4.1.1. Stormwater Calculations:

The Rational Method was used according to Subdivision and Development Servicing Bylaw No. 985 – Supplementary Design Guidelines Section 4.4 (areas under 10 hectares in size). 10-year event storm volumes were calculated to size the on-site storm water storage. 10-year and 100-year peak flow rates were determined to size minor and major systems, respectively, according to Sections 4.3.1 and 4.3.2.

4.1.1.1. Calculation Input Parameters

• IDF Data = Victoria-Gonzales
  • Intensity (24 hour 1:10-year storm event) = 74 mm / day
  • Intensity (24 hour 1:100-year storm event) = 105 mm / day
• Pre- and Post-Development runoff coefficients (C) were determined for the site
  • Pre-Development C = 0.520
  • Post-Development C = 0.760

See attached Appendix B for a detailed breakdown of the model input parameters.

4.1.1.2. Calculation Outputs

The following is a summary of the calculation outputs, detailing the pre-development and post-development flows as well as the required storage for both the 10- and 100-year rainfall events.

Storage Volume to be confirmed at detail design (building permitting)

• 10-year rainfall event:
  • Pre-development runoff = 37.4 L/s
  • Required storage = 22.2 m³
• 100-year rainfall event:
  • Pre-development runoff = 59.3 L/s

On-site storm water storage of 25 cu. m. will be provided via. rain gardens complete with a flow control manhole to limit storm discharge flow up to the 10-year rainfall event to pre-development flows. Refer to the Landscape design for on-site storm water storage configurations. Ultimate location and configuration will be confirmed during detailed design.

See attached Appendix B for a detailed breakdown of the calculation outputs.

It is recommended that the Town of View Royal review the storm calculation and confirm that the existing system has adequate capacity and/or the extent of any required upgrades.

4.2. SANITARY

The proposed flows including residential, peaking factor and infiltration is approximately 7.2 L/s. See attached Appendix C for detailed sanitary calculations.

It is proposed to connect to the existing 200 mm dia sanitary main along the Island Highway with a 200 mm dia sanitary service.

The sanitary flows from this development ultimately discharge to the View Royal Lift Station, owned and operated by View Royal. The View Royal Sanitary Master Plan completed in January 2019 recommends upgrades for sections of the gravity main feeding the View Royal Lift Station. These upgrades may be part of a DCC project for View Royal.

It is recommended that the Town of View Royal review the sanitary calculation and confirm that the existing system has adequate capacity and/or the extent of any required upgrades.

Sanitary sewer main in front of development may be undersized as a result of the development. This main requires upsizing unless future analysis as part of servicing agreement dictates that the development does not impact this section of sewer main.

4.3. WATER

The FUS fire demand is a function of the building construction materials, fire zone areas, separation distances and the use of sprinklers. The required fire flow based on the FUS calculation for the three buildings are as follows (see Appendix D) a) North Building = ~163 L/s b) East Building a. North of proposed vertical firewall = ~201 L/s b. South of proposed vertical firewall = ~223 L/s c) South Building = ~260 L/s

The South Building has the highest required fire-flow. therefore, that building will be used for the following analysis.

To determine whether the water system can provide the required fire flow, two criteria are typically analysed:

1. velocity of water in the system during the fire flow
2. flow available while maintain min. 20 psi in the system

1) Velocity:

The CRD has confirmed that the velocity of flow through a 250 mm main (existing condition) is above acceptable limits (maximum 3.0 m/s) and that a 300 mm dia water main shall be installed as part of the servicing requirements for this site.

2) Available Fire Flow:

The hydrant curve in Appendix E has been provided by the CRD. As noted, the hydrant data for Hydrant #VRFD161 is in excess of 500 L/s at a pressure of 20 pounds per square inch (psi). Based on the information provided by the CRD with a residual pressure of 20 psi, there appears to be adequate capacity in the existing system to satisfy this demand, although, the CRD has dictated upsizing the water main on Island Highway to 300 mm dia to meet maximum velocity requirements.

We recommend the Town of View Royal and CRD Water review the above calculations and confirm the existing systems have adequate capacity and/or the extent of any required upgrades.

This report was completed by McElhanney Ltd.

Nathan Dunlop, P.Eng. Project Manager

Alex Kaspryk, P.Eng. Project Engineer