to the new Broadway Drain. Sewer profiles were developed by Stantec Consulting for the entire PAR. Preliminary assumptions were made to establish the drainage parameters for the pending plaza drainage that will be detailed by others at a later date. The required drain profile was established by fixing the drain elevation at its upstream limit slightly lower than the lowest sewer invert, and then extending the drain to the Detroit River at a minimum longitudinal slope of 0.1%.

Application of the aforementioned design approach results in the large majority of the new channel invert being below the low water datum of the Detroit River. Our review of historic hydrographic data for the Detroit River revealed that the new channel will be predominantly inundated by backwater from the Detroit River. Even during dry weather periods, when there is no measurable flow occurring in the Broadway Drain, substantial water depths will occur.

Having due consideration for the hydrographic conditions that will persist in the new channel, and the resulting impact on dominant discharge velocities, the decision was made to design the channel more as an outlet canal. Based on hydrologic and hydraulic modeling completed over the course of this assignment, we concluded that a design capacity of 12.5 m3/s would be suitable for the sizing of the drain components.

In summary, we determined that it would be most appropriate to develop the channel improvements based on the following principles:

• Utilize an open, earth-lined trapezoidal channel section wherever practicable;

• Select channel side-slopes that are appropriate for the local soil conditions, in order to mitigate the potential for bank instability;

• Select a channel bottom width that provides sufficient channel capacity, based on the depth and shape of the channel;

• Where land ownership constrains the available width of the channel corridor, utilize an open, steel-lined rectangular section;

• Where necessary, utilize rock slope protection to mitigate the potential for bank recession; and,

• Where space permits, alter the section, alignment and edge treatment of the channel banks, in order to achieve fish habitat enhancement at varying water depths.

  6.7 Recommended Drain Improvements

Based on the information obtained during the site meeting, our examination and analysis of the survey data, and the hydrologic and hydraulic analyses conducted by Stantec and our office, we recommend the following improvements to the Broadway Drain:

• the enclosure of 780 metres of the Drain from Ojibway Parkway westerly to the existing intersection at Sandwich Street;

• the realignment, widening and deepening of 670 metres of the Drain downstream of the enclosed segment to the Detroit River to provide sufficient outlet;