SUBJECT: Eckardt Creek Erosion Control Optimization Study

PREPARED BY: Soran Sito, Senior Environmental Engineer

RECOMMENDATIONS:

That the staff report entitled “Eckardt Creek Erosion Control Optimization Study” dated October 16, 2007, be received;

And that staff be authorized to file the Eckardt Creek Erosion Control Optimization Study Class EA study with the Ministry of the Environment (MOE) for public review;

And that implementation of the retrofitting of the stormwater management pond (Bridal Trail Phases 3 and 4) to increase quality/quantity control be considered as part of the Markham Stormwater Strategy and future capital budget process;

And that Staff be authorized and directed to do all things necessary to give effect to this resolution.

EXECUTIVE SUMMARY:

On July 7, 2003, Markham Council authorized staff to undertake an erosion control optimization study for the Eckardt Creek (formerly called Burndenet Creek). The main objective of the study was to assess existing erosion conditions within the creek and to provide solutions for controlling erosion and improving the health of the Eckardt Creek. The Federation of Canadian Municipalities and the TRCA are assisting in the funding of this study.

The results of the study show urbanization south and north of 16^th Ave. contributing to a number of erosion problems within Eckardt Creek. Increased surface imperviousness and insufficient stormwater runoff controls south of 16^th Avenue have resulted in an increase in the quantity and the duration of the average instream flow in the creek. Three alternative options were investigated using criteria such as cost, feasibility, environmental benefits and social impact. The Town, TRCA, DFO, and the public have had the opportunity to discuss the range of technical issues related to the evaluation of the preferred alternative option.

In general, all parties agreed that restoring the creek naturally by increasing the control of storm runoff at the source was the preferred option. However, because of the

considerable limitations relating to availability and cost of land, retrofitting of the existing stormwater management ponds via increasing quality/quantity control will provide the greatest return on the investment in this project. Based on the results of the public meeting held on November 30, 2006, it was established that retrofitting of the Bridal Trail Phase 3 and Bridal Trail Phase 4 stormwater ponds located west of Eckardt Creek, south of 16^th Avenue (Figure -1) is the preferred option.

FINANCIAL CONSIDERATIONS:

The estimated range of costs to retrofit the Bridal Trail Phases 3 and 4 stormwater management ponds (two ponds) is in the range of $900,000 - $1,000,000. The retrofit work will be financed by development charges and pre-Development Charges Act Engineering Reserves. The retrofit work is to be considered in future capital budgets and as part of the Markham Stormwater Management Strategy program.

PURPOSE:

The purpose of this staff report is to seek Council’s endorsement of the above recommendations to address erosion problems in the Eckardt Creek and obtain authorization to file the Class Environmental Assessment.

BACKGROUND:

Eckardt Creek is located within the central part of the Town of Markham (Figure 1). It is a subwatershed of the Rouge River system. It flows in a southerly direction with 500 ha of total drainage area. Development south of 16^th Avenue was initiated in the 1980’s and completed in the 1990’s. North of 16^th Avenue the lands are currently being developed. A small percentage of the watershed north of Major Mackenzie Drive remains in a rural designation.

On July 7, 2003 Markham Council authorized staff to execute a grant agreement with the Federation of Canadian Municipalities (FCM) to undertake an erosion control optimization study for the Eckardt Creek. The FCM Green Municipal Fund Grant agreement provided $30,555 of funding for this study, with an additional $10,000 in funds from the TRCA. Because the Federal Government, Town of Markham, and the TRCA recognize the importance of maintaining a healthy environment and are also aware of the potential impact development may have on water courses, the Eckardt Creek Erosion Control Optimization Study was initiated.

The study objective may be defined as follows:

· Assess existing erosion conditions in Eckardt Creek and predict future erosion based on a number of different stormwater management scenarios.

· Evaluate the effectiveness of the various stormwater management scenarios and select a preferred scenario.

· Once the preferred scenario has been selected, undertake the detail design, construction supervision and monitoring of effectiveness of the proposed works.

The 5 phases of the Eckardt Creek Erosion Control Optimization Study and the status of each phase are described in Table-1 below:

Table-1: Project Phases & Status

Phase	Description	Status
Phase I	Background review, problem identification, selection and evaluation of alternative stormwater management options	Completed
Phase II	Select the preferred stormwater management option. Complete the Class Environmental Assessment of the preferred option	Completed
Phase III	Detail design and a tender package for the preferred option will be developed, and the proposed works will be constructed	Subject to budget approval
Phase IV	Implement the environmental monitoring program to confirm the long term impact of urbanization	Subject to budget approval
Phase V	A report summarizing the findings from the first four phases will be prepared	Subject to budget approval

Town staff and their consultant have completed Phase I and II of the study. Phases III, IV and V are subject to Council approval of the required funding. The Class EA document for this study will be filed with the Minister of the Environment before the end of 2007.

OPTIONS/DISCUSSION:

Problem Identification

As a result of urbanization, a number of potential problems have been identified within Eckardt Creek. These problems include:

• Excessive sediment loadings to the creek as part of upstream development and construction process
• Loss of in-stream aquatic habitat
• Loss of vegetation (including mature trees) adjacent to the stream
• Loss of channel stability within Eckardt Creek which, as a result of excessive sediment loadings, will adversely impact water quality conditions, fish habitat and potentially private/public property
• Reduction in base flow to the channel.

Establishing Existing Conditions

Existing conditions were established by reviewing existing documents, undertaking a hydrologic analysis and determining the stability of Eckardt Creek via a field program. The above noted activities will also be of assistance for determining the impact of proposed development.

The field program focused on the natural portion of the stream (i.e.: from approximately 500m north of 16th Avenue downstream to the confluence of Eckardt Creek and the Rouge River – refer to Figure 1). Photographs illustrating representative segments of the stream channel were taken. Furthermore, the data which characterized the morphology of the stream (i.e.: channel gradient, pool/riffle structure, channel dimensions, boundary material, vegetation type) was collected.

The objective of the field program was to characterize existing stream conditions and to provide a benchmark for assessing the potential impact of future development as well as the effectiveness of alternative stormwater management strategies.

The results of the field program which was undertaken in 1999, 2003 and 2006 show that Eckardt Creek has been significantly degraded. Furthermore, the stream continues to respond to the impact of development in the upstream reaches.

Establishing Options

In order to address the above noted concerns, 3 stormwater management options were investigated. These stormwater management options were categorized into 4 groups as shown in Table-2 below:

Table-2: SWM Groups & Alternative Options

SWM Groups	Options
Source control measures	Option 1: construction of an underground infiltration facility in a recently constructed park located north of Bur Oak Avenue between the Bridle Walk and Glenbrook Drive. The proposed facility (6,000m^3) would reduce flow volumes entering the stream from approximately 50ha of lands located upstream of this location. The estimated cost for this project is approximately $2 million.
Infiltration measures
Modification to existing stormwater management facilities to improve water quality and/or quantity control	Option 2: retrofitting two existing stormwater management ponds, Bridal Trail Phases 3 and 4 Ponds (identified in the Town of Markham Stormwater Retrofit Study as ponds 88.0 and 88.1). Both facilities are located south of 16^th Avenue, west of Eckardt Creek (Figure 1). Retrofitting of these facilities would reduce the impact of erosion and improve water quality conditions (an initiative that was also identified in the Town of Markham Stormwater Retrofit Study). The estimated cost to retrofit the two facilities is in the range of $900,000 - $1,000,000.
Stream restoration measures	Option 3: restoring approximately 500m of the Eckardt Creek from 16^th Avenue southerly to approximately the green space off Longwater Chase. This section of stream was selected as it is being impacted by, and continue to respond to, upstream and adjacent urbanization which has implications not only for the reach along which it is situated, but also for the destabilization of downstream reaches. The total cost for the channel restoration is approximately $500,000.

Selection of the Preferred Option

In addition to developing a long term approach to protect, enhance and restore Eckardt Creek, selection of the preferred option also involved consideration of land cost, feasibility of implementation, environmental benefits, and social impact.

The environmental benefits and the feasibility of construction of the underground infiltration facilities (option 1) were limited due to:

• significant lack of land availability, as well as cost of land in the area
• soil material within the lands south of 16^th Ave. consists mostly of silty clay with low infiltration capacity
• the location and grading of the available parkland for infiltration would provide only minimum infiltration.

The restoration of 500m of Eckardt Creek south of 16^th Ave. (option 3) was not recommended at this stage of the study because:

• since lands north of 16^th Ave. have recently experienced landuse change (urbanization), more monitoring data is required to clearly understand the causes

of erosion south of 16th Ave. and associated impact from recent development north of 16^th Ave.

• only limited water quantity and quality control can be achieved.

Retrofitting of the Bridal Trail Phase 3 and Bridal Trail Phase 4 ponds (option 2), was selected as the preferred one because option 2:

• is easy to implement
• provides the greatest return on the investment
• provides a long term source control of runoff quality and quantity
• is consistent with the recommendations of the Markham Stormwater Retrofit Study.

Based on the above, option 2 was selected as the preferred option for this study. In addition, as part of phase IV, additional instream monitoring and data collection is required to further understand the impact from recent development north of 16^th Ave. on the section of Eckardt Creek south of 16^th Avenue. The findings from the monitoring program will be used to assist in determining whether instream work is needed to restore the creek. The location and type of work, if necessary, would then be assessed.

Undertaking of Municipal Class EA for the Retrofitting of Bridal Trail Phases 3 and 4 Stormwater Management Facilities

The Environmental Assessment (Phase 2 of the overall project) has been initiated. The study, which is being carried out under Schedule B of the Municipal Class EA process, will define the Preferred Conceptual Design for each of the two facilities. To-date, the Notice of Commencement has been filed and alternatives for each facility have been filed. A Public Open House meeting was also held on November 01, 2006 at the Town of Markham Civic Centre. The Open House included display boards illustrating the problems and alternative solutions together with a questionnaire. Approximately 10 local residents attended the meeting. General questions with respect to aesthetics and West Nile Virus were addressed.

FINANCIAL TEMPLATE:

To be considered under future capital budgets.

ENVIRONMENTAL CONSIDERATIONS:

The implementation of the recommendations provided in this report, with the assistant of the Federation of Canadian Municipalities and the TRCA, should result in improved protection of the Eckardt Creek as a vital water course and a natural heritage system within the Eckardt Creek subwatershed. As such, an overall interest exists within most

government levels in promoting the protection of water courses and enhancing the long-term social and environmental benefits.

ACCESSIBILITY CONSIDERATIONS:

None

ENGAGE 21^ST CONSIDERATIONS:

The findings and recommendations of the Eckardt Creek Erosion Control Optimization Study are aligned with the Environmental Focus goal of the Town’s Engage 21^st Markham Strategic Plan.

BUSINESS UNITS CONSULTED AND AFFECTED:

The Eckardt Creek Erosion Control Optimization Study has been prepared in consultation with the Operations and Asset Management Departments and their comments have been incorporated.

RECOMMENDED BY:

__________________________ __________________________

Alan Brown, C.E.T. Jim Baird, M.C.I.P., R.P.P.

Director of Engineering Commissioner of Development Services

ATTACHMENTS:

Attachment A: Figure 1 - Location map

Q:\Development\Engineering\REPORTS\2007\October\Eckardt Creek Erosion Control Optimization Study 101607.doc