11. SAWMILL CREEK EROSION PROTECTION
WORKS – ENVIRONMENTAL ASSESSMENT RECOMMENDATIONS RECOMMANDATIONS
DE L’ÉVALUATION ENVIRONNEMENTALE DE PORTÉE GÉNÉRALE CONCERNANT LES TRAVAUX DE
PRÉVENTION DE L’ÉROSION DU RUISSEAU SAWMILL |
Committee recommendationS
That
Council:
1. Confirm the preferred solutions identified in the Sawmill Creek Erosion Protection Works Class Environmental Assessment, as shown in Document 6.
2. Direct staff to finalize the Sawmill Creek Erosion Protection Works Class Environmental Assessment and proceed with the 30-day public review period, in accordance with the Ontario Environmental Assessment Act.
3. Approve the proposed pilot project (Project 1) to implement and monitor a series of "submerged stream barbs," for which the Federation of Canadian Municipalities’ Green Municipal Fund has approved 50 per cent funding of a total project budget of $132, 000.
RecommandationS du Comité
Que le Conseil:
1. confirme
les solutions privilégiées dans le cadre de l’évaluation environnementale de
portée générale concernant les travaux de prévention de l’érosion du ruisseau
Sawmill, qui sont illustrées dans le document 6.
2. demande au personnel de finaliser l’évaluation
environnementale de portée générale concernant les travaux de prévention de
l’érosion du ruisseau Sawmill et de lancer la période d’examen public de 30
jours, conformément à la Loi sur les évaluations environnementales de l’Ontario.
3. approuve le projet pilote proposé (projet 1),
qui vise à mettre en place et à surveiller une série de barbelures immergées,
étant donné que la Fédération canadienne des municipalités a accepté de
financer 50 p. 100 du coût total du projet, qui s’élève à 132 000 $,
par le biais de son Fonds municipal vert.
Documentation
1.
Deputy
City Manager's report Planning, Transit
and the Environment dated 25 April 2008 (ACS2008-PTE-PLA-0102).
2. Extract of Draft Minutes, 13 May 2008.
Report to/Rapport au :
Planning and
Environment Committee
Comité de l'urbanisme et de l'environnement
25 April 2008 / le 25 avril 2008
Submitted by/Soumis par : Nancy Schepers, Deputy City Manager
Directrice municipale adjointe
Planning, Transit and the
Environment
Urbanisme, Transport en commun et
Environnement
Contact Person/Personne ressource : Vivi Chi, Manager,
Transportation
and Infrastructure Planning
Planning
Branch/Direction de l'urbanisme
(613)
580-2424, ext. 21877 Vivi.Chi@Ottawa.ca
Carol
Christensen, Manager, Environmental Sustainability
Economic
and Environmental Sustainability Branch
(613)
580-2424, ext. 21610 Carol.Christensen@Ottawa.ca
REPORT RECOMMENDATION
That Planning and
Environment Committee recommend Council:
1. Confirm the preferred solutions identified in the Sawmill Creek Erosion Protection Works Class Environmental Assessment, as shown in Document 6.
2. Direct staff to finalize the Sawmill Creek Erosion Protection Works Class Environmental Assessment and proceed with the 30-day public review period, in accordance with the Ontario Environmental Assessment Act.
3. Approve the proposed pilot project (Project 1) to implement and monitor a series of "submerged stream barbs," for which the Federation of Canadian Municipalities’ Green Municipal Fund has approved 50 per cent funding of a total project budget of $132, 000.
RECOMMANDATION DU RAPPORT
Que le Comité de l’urbanisme et de
l’environnement recommande au Conseil :
1. de
confirmer les solutions privilégiées dans le cadre de l’évaluation
environnementale de portée générale concernant les travaux de prévention de
l’érosion du ruisseau Sawmill, qui sont illustrées dans le document 6.
2. de
demander au personnel de finaliser l’évaluation environnementale de portée
générale concernant les travaux de prévention de l’érosion du ruisseau Sawmill
et de lancer la période d’examen public de 30 jours, conformément à la Loi
sur les évaluations environnementales de
l’Ontario.
3. d’approuver
le projet pilote proposé (projet 1), qui vise à mettre en place et à surveiller
une série de barbelures immergées, étant donné que la Fédération canadienne des
municipalités a accepté de financer 50 p. 100 du coût total du projet, qui
s’élève à 132 000 $, par le biais de son Fonds municipal vert.
BACKGROUND
The Sawmill Creek Subwatershed Study Update adopted by Council in 2003 (http://ottawa.ca/calendar/ottawa/citycouncil/esc/2003/09-09/ACS2003-DEV-POL-0034.htm) identified erosion concerns on reaches of the creek between Heron Road and Bank Street. Based upon subsequent investigations, two sites were identified for remedial works:
i) Project 1: North of Heron Road (adjacent to Clover Street);
ii) Project 2: North of Heron Road (adjacent to Lasalle Street).
The locations of both projects are identified on Document 1 and a brief description of each project follows.
Project 1:
This project is a partnership between the City and the University of Ottawa. In August 2005, the City was approached by Dr. Colin Rennie, an engineering professor at the University of Ottawa, to partner on a grant proposal to the Federation of Canadian Municipalities’ Green Municipal Fund (GMF) for the field testing of a series “submerged stream barbs.” Stream barbs are linear rock structures installed along the eroding outer bank of a stream bend. Their purpose is to redirect flow away from the eroding bank which, in this case, will prevent undermining of the valley slope of Sawmill Creek.
Given that the City has numerous urban streams subject to on-going erosion, it was decided that this would be a good opportunity to test this relatively low-cost, “fish-friendly” approach to erosion protection. The site adjacent to Heron Park (Project 1 location) is a steep valley wall subject to undermining.
Although there is no imminent threat to infrastructure or the park property, continued erosion will increase the risk of slope failure with time. Therefore the site will benefit from the installation of stream barbs, but the current risk is low, making this a more suitable site for a pilot project.
Based upon what is learned from this pilot, the use of stream barbs to address erosion concerns at other suitable sites will be able to be applied with greater confidence.
The City's application to the GMF was successful and in March of 2007, the GMF approved 50 per cent funding of the total project cost. The project budget is approximately $132,000 which includes design (by the University), construction (to be tendered) and monitoring (City staff and the University) as well as the preparation of a design guideline to promote broader application of this method (the University).
Project 2:
This project is located just downstream of the Project 1 site. Subsequent to the Sawmill Creek Subwatershed Study Update (2003), a follow-up fluvial geomorphology assessment of the creek was completed in 2005 and one high priority site was identified for remedial works. This site is characterized by a steep bank where the natural bend in the creek was encroached upon to provide room for construction of the Transitway. Active erosion is occurring at the site increasing the risk of slope failure which, with time, will threaten infrastructure. The proposed solution is to adjust the alignment of the creek away from the toe of slope. The project budget is approximately $270,000.
DISCUSSION
Erosion protection works fall under Schedule "B" of the Municipal Class Environmental Assessment (Class EA), requiring the completion of Phases 1 and 2 of the Class EA Planning and Design Process. The scope of this process includes:
i) Defining the Problem;
ii) Documenting Existing Conditions;
iii) Identifying, Evaluating and Selecting the Recommended Solutions; and
iv) Publishing a Notice of Completion.
Defining the Problem:
Active erosion is occurring at two sites on Sawmill Creek, threatening adjacent property and infrastructure.
Documenting Existing Conditions:
Sawmill Creek flows through a heavily developed section of the subwatershed, however, there is good riparian cover along most of the creek corridor due to a deep, well-defined valley. The creek is in a transitional state, with some unstable areas due to active erosion and deposition processes. This reflects a flow regime that is heavily influenced by urban drainage. The creek is also constrained by the Transitway and the Airport Parkway.
Water quality along this reach has periodic high levels of bacteria, phosphorus and suspended solids. The fish community is characterized by warm water fish although the average water temperature is below 20°C. Straight sections of channel, urban runoff and beaver dams contribute to the lack of fish diversity in the system.
The soils in the area are generally clays and clayey silts (marine sediments).
Detailed fisheries monitoring of the two project sites is also being completed by City staff this spring to allow for a pre- and post-construction comparison of the fish community.
Identifying, Evaluating and Selecting the Recommended Solutions:
A qualitative evaluation of three alternative solutions for each project site was undertaken and is summarized in Document 2.
For Project 1, the three alternatives considered included:
1. "Do nothing;"
2. Toe protection (riprap): placing rock riprap at the toe of the slope to prevent further local erosion; and
3. Submerged stream barbs: linear rock structures located along the eroding bank that deflects flows away from the bank toward the center of the creek.
Concepts for each of the three alternatives are provided in Document 3.
Alternative 1 (“Do nothing”) is not a feasible option as continued erosion will ultimately impact the park. Alternatives 2 and 3 (toe protection and submerged stream barbs, respectively) would have similar impacts on the park during the construction period, for example, machinery accessing the valley, storage of construction materials, etc. Alternative 3 (stream barbs) is less expensive than Alternative 2 (toe protection), has greater potential for enhancing existing fish habitat, and allows for increased riparian vegetation that will contribute to greater slope stability. Based on this qualitative evaluation, Alternative 3 (submerged stream barbs) is selected as the preferred solution.
For Project 2, the three alternatives considered included:
1. "Do nothing;"
2. Toe protection (riprap): placing rock riprap at the toe of the slope to prevent further local erosion; and
3. Channel realignment: creating a new channel located further away from the eroding slope by cutting off the meander bend.
Concepts for each of the three alternatives are provided in Document 4.
Alternative 1 (“Do nothing”) is not an option as continued erosion will eventually threaten existing infrastructure (the Transitway). Alternatives 2 (toe protection) and 3 (channel realignment) would have similar impacts during the construction period, for example, machinery accessing the valley, storage of construction materials, etc.
The construction cost of Alternative 3 (realignment) is greater than Alternative 2 (toe protection) however, this cost does not consider the long-term maintenance cost of the riprap to protect the slope. Because of the long term maintenance associated with Alternative 2, Alternative 3 would provide greater long-term protection since the creek would be relocated away from the slope. Alternative 3 (realignment) also has greater potential for enhancing existing fish habitat. Based on this qualitative evaluation, Alternative 3 (realignment) is selected as the preferred solution.
Publishing a Notice of Completion:
Subject to Council adoption of the Class EA recommendations, a notice of completion will be published to initiate the 30-day public review period.
ENVIRONMENTAL IMPLICATIONS
The preferred solutions will have some negative impacts on the existing valley during the construction period as a result of the need for machinery to gain access, some vegetation removal and disturbance to the low flow channel to install the works. However, these impacts will be minimized to the extent possible through construction methods, proper sediment and erosion control, and re-planting of disturbed areas. Environmental benefits anticipated include improved fish habitat, reduced harmful erosion, and increased slope stability.
CONSULTATION
Public consultation for these projects has included the following:
i. Technical Advisory Committee: This Committee (TAC) reviewed and commented on the Class EA and preferred solution for each site. The TAC is comprised of representatives from the Ministry of the Environment, the Rideau Valley Conservation Authority, the National Capital Commission, and City staff.
ii. A Notice of Study Commencement and Open House was advertised in the Citizen and Le Droit on March 21 and March 28, 2008.
iii. Open House: An Open House was held on April 1, 2008 to present the projects to the public and request their comments. A total of seven people attended the Open House. Document 5 provides a summary of the comments provided along with staff responses.
iv. Website: A project website went live in March 2008 and will be updated regularly.
FINANCIAL IMPLICATIONS
Funding for the detailed design and construction of Project 1 (submerged stream barbs) is available in capital accounts 900985 - Stormwater Master Plan and 902203 - Stream Restoration Projects. Upon completion of Project 1, the City will be reimbursed for 50 per cent of the total project cost by the Green Municipal Fund.
A funding request for Project 2 (channel realignment) will be brought forward for consideration in the 2009 budget.
SUPPORTING DOCUMENTATION
Document 1 - Location Plan
Document 2 - Evaluation of Alternative Solutions
Document 3 - Project 1 Alternative Solutions
Document 4 - Project 2 Alternative Solutions
Document 5 - Comments from Open House
Document 6 - Preferred Solutions
DISPOSITION
Planning, Transit and the Environment Department staff will finalize the Sawmill Creek Erosion Protection Works Class Environmental Assessment and file the Notice of Completion to initiate the 30-day public review period.
Once the Class EA is approved under the Environmental Assessment Act, staff will coordinate the detailed design, approval and construction of the erosion protection works.
LOCATION MAP
DOCUMENT
1
EVALUATION OF ALTERNATIVE SOLUTIONS DOCUMENT 2
PROJECT 1 ALTERNATIVE SOLUTIONS
DOCUMENT
3
Project 1 - Alternative 1: “Do
Nothing”
Project 1 – Alternative 2: Toe Protection (Riprap)
Project 1 – Alternative 3: Submerged
Stream Barbs
PROJECT 2 ALTERNATIVE SOLUTIONS DOCUMENT 4
Project 2 - Alternative 1: “Do Nothing”
Project 2 –
Alternative 2: Toe Protection (Riprap)
Project 2 – Alternative 3: Channel Realignment
COMMENTS FROM OPEN HOUSE DOCUMENT
5
PREFERRED SOLUTIONS DOCUMENT
6
Project 1 Preferred Solution: Submerged Stream Barbs
Project 2 Preferred
Solution: Channel Realignment
