Westbrook Consulting Ltd. - Re: 231 Heddle Avenue – Site Servicing Concept
Technical memorandum regarding conceptual sanitary sewer, storm drain, and water infrastructure for the development.
January 17, 2018
3214-02
Sterling Plaza Inc. | K.Star Home Improvements c/o Praxis Architects Inc. 401-1245 Esquimalt Road. Victoria, BC V9C 3J2
Attn: Gerry Conrod | John Koren
Re: 231 Heddle Avenue – Site Servicing Concept
Dear Sirs:
Westbrook Consulting Ltd. has prepared a preliminary site servicing concept plan for the development of 231 Heddle Avenue.
Background
The existing site at 231 Heddle Avenue contains one single family home. The site slopes steeply from the center down towards the property boundaries. One single family home with a gravel driveway and parking area has been constructed on the site. The center of the site is cleared and rock has been exposed. Towards the outer edges of the site boundaries there are forest covered slopes that are expected to be retained.
Sanitary Sewer
The site is currently serviced by a 150 mm diameter PVC sanitary sewer main on Island Highway, through a right of way on 321 Island Highway. There is an existing 150 mm diameter PVC sanitary sewer main on Heddle Avenue. The main terminates at 240 Heddle Avenue and will be required to be extended to service the development, as shown in the enclosed Servicing Concept Figure. The existing right of way can then be eliminated.
Storm Drain
The storm water produced by the site currently infiltrates naturally onsite or flows to the existing ditch and drain system on Heddle Avenue. Storm water management will be required to ensure that the additional runoff created by the development is controlled and released at the pre-development flow rate. The storm water management system will consist of a rain garden and a detention gallery that will release the storm water at the pre-development flow rate to the vegetated area fronting the site.
The storm water collected from the building rain water leaders will flow through rock swales to the rain garden. Storm water produced by the driveway will be captured in catch basins and stored in the detention gallery. The driveway area fronting Building 1 will also be constructed out of permeable pavers to reduce the quantity of runoff produced by the development.
The system will have an over flow directly to the storm drain system on Heddle Avenue in the event of a storm that exceeds the system capacity.
Water
The site is currently serviced by a 150 mm diameter PVC water main on Heddle Avenue. Preliminary fire flow calculations have been performed and it has been determined that the existing water main has sufficient flow and pressure to supply water to the proposed development. The calculated velocity under fire flow conditions of 8.29 m/s exceeds the maximum allowable velocity of 3.5 m/s, as per CRD Engineering Specifications. Consultation with the CRD will be required to determine the extent of upgrading required.
We also understand that a backflow prevention chamber will be required at the property line. A preliminary water servicing layout can be seen in the enclosed Servicing Concept Figure.
Summary
The site will be serviced by existing sanitary sewer, storm drain, and water infrastructure on Heddle Avenue. A storm water management system composed of a variety of storm water management techniques will be required to limit the storm water runoff from the site to that of pre-development conditions. The existing sanitary sewer main along Heddle Avenue will require an extension to service the development and a portion of water main on Heddle Avenue from the site to Prince Robert Drive may require upgrading; further consultation with the CRD is required.
If you have any questions please do not hesitate to contact the undersigned.
Yours truly,
WESTBROOK CONSULTING LTD.
Tracey Klatt, EIT Project Engineer
Reviewed by,
Mike Wignall, P.Eng, LEED AP Project Manager
ENCL: SERVICING CONCEPT FIGURE
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