Terms of Reference
Retrofit of the Conroy Road Snow Disposal Facility
1.0 Project Overview
The City of Ottawa wishes to obtain construction services in order to restore functionality to
the Conroy Road Snow Disposal Facility as per MOE ECA 3-0705-92-006; specifically:
·
Repair of the riser outlet structure;
·
Sediment removal from the existing forebay and first 15 meters of the main cell;
·
Re-establishing the east-west drainage ditch:
·
Erosion pad for the existing north-south drainage ditch; and,
·
Approximately 150 meters drainage ditch to connect with the existing north-south
drainage ditch.
·
Return of the facility to service.
2.0 Background
The Conroy Road Snow Disposal Facility (facility) was constructed in 1992 and is one of four
snow melt-water facilities located within the City of Ottawa (City). The facility is located west of
Conroy Road and south of St. Laurent Boulevard with GPS coordinates of Lat. 45.376564 by
Long. -75.628233. The facility is designed to control suspended solids of the snow melt-water
facility to less than 80 mg/l at a snow melt design of 140 l/s and to discharge the settled snow
melt-water through an overflow outlet structure located at the east end of the facility to a 600
mm diameter storm sewer. As detailed in the MOE ECA, the facility’s design consists of:
·
A horse-shoe shape snow melt-water management pond with a surface area of 0.32
hectare and a maximum water depth of 1.7 meters;
·
An approximately 54 meters long by 5 meter wide swale with a slope of 0.5%;
·
An outlet structure consisting of a Hickenbottom riser, filter cloth and clear stone;
and,
·
A head wall and bypass gate.
The City of Ottawa Stormwater Management Unit is responsible for the operations, maintenance
and inspections of the City’s stormwater facilities. Annual inspections of the Conroy Road
Snow Disposal Facility have revealed that the facility is not operating as designed and is in need
repairs, specifically that:
·
The clear stone filter at the outlet riser has become impregnated with clay;
·
The existing sediment forebay has become loaded with clay sedimentation;
·
The existing forebay is not sized properly for optimum performance,
·
The first 15 meters of the main cell has become sedimented;
·
The north east section of the snow melt-water facility is not draining to the facility;
·
The east-west drainage ditch has been dug out during an on-site flooding incident where
the rip-rap and geotextile erosion protection was removed/damaged; and
·
The existing north-south drainage ditch has no erosion pad;
3.0 Anticipated Scope of Work
·
Removal of the 25 mm clear stone and filter cloth at the riser and replace with clean 25
mm clear stone and replace the filter cloth with a size appropriate (for the 25 mm stone)
stainless steel mesh;
·
Removal of approximately 50 cubic meters of sediment from the main cell;
·
Removal of approximately 50 cubic meters of sediment from the sediment forebay;
·
The sediment will be managed on-site;
·
Enlargement of the sediment forebay to approximately 15 meters wide by 30 meters long
and lined with Amoco 4547 or equivalent and rip-rap as per OPSD 810.02 Type B, 300
mm thick (blue lines on Aerial photo);
·
Realign approximately 63 meters of the east-west drainage ditch to the expanded forebay
with the slopes of the banks no steeper than 4:1. The ditch will be lined with Amoco 4547
or equivalent and rip-rap as per OPSD 810.02 Type B, 300 mm thick (red line on Aerial
photo);
·
Construction of an erosion pad for the north-south ditch outlet consisting of Amoco 4547
or equivalent geotextile and 100-300 mm blast rock, 500 mm thick (red line on the Aerial
photo);
·
Reinstatement of approximately 150 meters of drainage ditch on the north-east corner of
the facility and connecting to the existing north-south drainage ditch. The dimensions of
the new ditch will be the same as the existing north-south ditch. The ditch will be seeded
with all purpose seed (green line on Aerial photo);
·
Realignment or construction of berms if/as required; and,
·
Contouring of the immediate area to promote positive drainage.
4.0 Summary of Deliverables
1. Obtain locates and all applicable permits and approvals as required.
2. Implement an appropriate sedimentation plan for the identified work.
3. Conduct the repairs to the facility that is summarized in 2.0 Background and 3.0 Scope of
Work.
4. Reinstate the landscaping as required.
5.0 Supporting Documents
·
Drawing C1.1from project CM-09-146
·
Aerial view detailing the location of the identified works.