to the Grand Marais Drain. Mr, Krutsch responded that currently there is only one outlet from the Marentette-Mangin Drain to the Grand Marais Drain.
A record of the on-site meeting is provided in Appendix C.
4.0 Field Surveys and Investigations
Due to the quality of available topographic information throughout the watercourse, a limited amount of survey work was needed to complete our examinations and this report.
The existing topography of the drain was acquired from:
LiDAR data obtained from Land Information Ontario. Accordingly, the base mapping for this project contains information licensed under Open Government License - Ontario;
information contained in as-built drawings of the Huron Estates Subdivision (hereafter Huron Estates) prepared by R. Meo and Associates Inc. in 1994; and,
localized topographic surveys by Landmark staff to infill data gaps and confirm the existing channel profile.
For the purpose of ground-proofing the foregoing information and data, and confirming the condition of the existing drain, an inspection of the entire drain was undertaken by Landmark in December 2018.
5.0 Design Considerations
A recent document published by OMAFRA (Publication 852) entitled “A Guide for Engineers working under the Drainage Act in Ontario” is the current reference document used by engineers carrying out works under the Act. That document addresses the application of Drainage Act, 1990 requirements and other regulations, policy and legislative aspects of completing drainage undertakings. The document also provides guidelines on the technical design components of engineering reports.
5.1 Design Event / Level of Service
Historically, the drainage standard that has been applied to most municipal drains in rural Ontario is the 2-year storm, a storm return period that has a 50% chance of occurring each year. In residential and commercial areas, the 5-year and 10-year events are recommended due to the increase risk of flooding or where the location of flooding may result in significant losses. These events have chances of occurring of 20% and 10% respectively. The Act assigns the responsibility for selection of an appropriate design storm / level of service to the appointed engineer. Due to the occurrence of the Huron Estates Subdivision within the watershed, and the need to ensure that an appropriate degree of flood proofing is provided to those lands, the 5-year and 100-year event have been adopted as the design event for the drain.