`		COMMITTEE OF THE WHOLE
	TO:	Mayor and Members of Council
	FROM:	Peter Loukes, Director, Operations
	PREPARED BY:	same as above
	DATE OF MEETING:	November 29^th, 2005
	SUBJECT:	August 19, 2005 Storm Review

RECOMMENDATION:

THAT the report entitled “August 19, 2005 Storm Review” be received;

AND THAT Staff be directed to continue to monitor the damage caused by the storm and to report back to Council regularly on the status.

PURPOSE:

Staff has prepared this report to affirm the details of the August 19^th storm event that have been presented to Council in verbal presentations on August 29^th, September 1^st and 27^th.

The purpose of this report is to provide Council with information on;

• The performance of the Towns sanitary and storm drainage systems
• The events of the day and staff’s response, and;
• The assessment of the damages to public infrastructure

BACKGROUND:

The following provides a background of the events and activities on August 19, 2005.

Thunderstorm Warnings issued for Markham and major storm grates inspected

Operations Staff continually monitor weather conditions throughout the year, utilizing Environment Canada’s observation station at Buttonville Municipal Airport and when storm advisories are issued, they are monitored directly by the Supervisors. On August 19, 2005, rain and thunderstorms were forecast for the morning with further thunderstorms were identified for the afternoon period. In response, staff had conducted site inspections at the major storm grates to ensure that they were clear to handle the run-off from the anticipated storms.

The storm on August 19^th formed from severe weather in Southern Ontario

According to our research on the events of that day, severe weather was being forecast for Southern Ontario and at 1:00 p.m. on August 19^th, Environment Canada upgraded their previous severe thunderstorm watch to a tornado watch for the Fergus Ontario area. It would be later determined that by 2:00p.m. a strong tornado had touched down in that area. Though that tornado did dissipate, the storm that generated it continued to move east and a narrow band of intense rain fell through Brampton, Vaughan, Markham, the north end of Toronto, and then on to Pickering, Ajax, Whitby, and Oshawa.

Storm Drainage Systems

Like all municipalities in Ontario, the Town of Markham follows the guidelines for both sanitary and storm drainage systems established by the Ontario Ministry of Environment. Rainfall events and subsequent surface drainage are not factors consider in sanitary drainage system design. The storm drainage system design includes the design of a minor system (storm sewers) and a major system (overland flow routes, storm water management ponds, etc.). Rainfall events are measured by the average frequency of occurrence of events having a given volume and duration. For example: a 2 year; 10 year; or 100 year storm.

Generally storm sewers are designed to accommodate a 5 year design storm which would operate without surcharge during a 100 year storm event. Inlet control devices are utilized to control the flow of water into the storm sewer system to prevent surcharging during major storm events. Major storm systems are designed to accommodate a 100 year design storm that convey overland flows to storm water management ponds and/or natural or manmade conveyance systems without threat of flooding to private property.

Intense rainfall in some areas of Markham exceeded the 100 year storm levels

There are several rain gauges located around the Town and monitored and maintained by different agencies. Here are the results of the rainfalls on August 19^th from those gauges.

Location	Operated by	Rainfall Observed	Period
Leslie Street Pumping Station	Region of York	105mm (4.13 in)	3 hours
Armadale CC	Town of Markham	98 mm (3.85 in)	2 hours
Civic Centre	Town of Markham	75mm (2.95 in)	2 hours
Buttonville Airport	Environment Canada	54mm (2.13 in)	All day
Royal Orchard & Bayview	Private	133mm (5.24)	2 hours
Yonge & Steeles	Private	175mm (6.89)	All day

Based on the Town’s storm design criteria the rainfall expected from a 100 year return storm would be estimated at 68mm (or 2.68 inches) in 2 hours and 73mm (or 2.87 inches) in 3 hours. For all rain stations south of Buttonville Airport, these thresholds were exceeded – illustrating that roughly the Thornhill and Milliken areas of Markham, in whole or in part, received rainfalls in excess of the 100 year storm level. Considering the severe intensity of this storm, a storm drainage system designed in accordance with the Ministry of Environment guidelines could not possibly control the runoff from this storm through either the minor or major systems.

DISCUSSION:

Widespread Damage

The majority of the damage to the infrastructure was restricted to the area south of Highway 407, with localized areas throughout the Town. Thornhill received the bulk of the damage, which consisted of flooded roads, watercourses, stormwater management ponds, basements, trees blown down, or eroded to the extent that they fell.

Immediate action taken by Operations staff

On the evening of August 19^th, Operations staff responded to a great number of flooding calls; streets flooding, basements flooded, manhole covers displaced, culverts blocked, storm grates covered with debris, shoulders/driveways eroded and trees down. Once the rain and flooding subsided, work crews cleared felled trees and branches from roads, cleaned storm and catch basin grates to remove any restrictions and replaced manhole lids.

Where staff either found or were informed by residents of potential hazardous conditions where roads, bridges, and pathways were washed out, they undertook to place barricades, and signage identifying lane closures, and or unsafe conditions. These locations were monitored throughout the weekend to ensure barriers remained in-place.

Upgraded Standby Workforce put in place

On the evening of the storm, nineteen Operations staff remained on duty and kept the Operations phone line open to assist the Contact Centre and Information Markham with overflow calls and respond to emergencies.

The staff was coordinated to respond to the storm throughout the evening of August 19, 2005. Many of the staff were on duty until mid-night, and then returned the following morning to further investigate known damaged areas, and investigate additional queries.

Contractors who provide various equipment and services were put on notice that they may be required that evening or throughout the weekend. On the evening of the storm loaders and backhoes were mobilized to clear the major storm grates of debris and to assist with drainage

Emergency Operations Centre Activated

The Town Emergency Plan was activated and through consultation with the Mayor, a selected portion of the Markham Control Group (MCG) was put on alert and asked to assemble at the Emergency Operations Centre on Saturday, August 20^th. The MCG, chaired by Commissioner Sales, co-ordinated the ongoing response, identified damaged areas and additional resources required to reinstate our infrastructure. Additional meetings were held the following week and the chair has been updating Council and senior staff on a regular basis.

Follow up and ongoing repairs to infrastructure

To date the Operations Department has completed numerous repairs to address road base failures and damaged asphalt surfaces throughout sections of the Town located between Steeles Avenue and Highway 407. In addition, Operations staff has undertaken repairs to washed out areas of Parks pathways and rural road gravel shoulders throughout the Town.

Waterworks staff have completed sewer flushing and visual inspection of sanitary systems in the hardest hit areas.

Long Range Action Plan

The Operations Department has several locations where the effects of the storm have caused severe damage to watercourses, pedestrian bridges and pathways. The Operations and Asset Management group will continue to work with external agencies including the Toronto and Region Conservation Authority, Ministry of Natural Resources, and Department of Fisheries and Oceans to coordinate the detailed design and obtain the necessary permits to undertake the required repairs and restoration.

Peter Loukes, P.Eng Director, Operations

Jim Sales, Commissioner, Community and Fire Services

Q:\Commission Share\Operations and Asset Management\Reports\2005\Peter Loukes\August 19.Storm Report for Peter.doc