1.0 PURPOSE

To: Community Services Committee

Stan Bertoia Commissioner

The purpose of this report is to update Council following the engineering stormwater modeling study and wildlife expert assessment of the beavers management issue at the Goodman Creek Stormwater Management Pond.

2.0 RECOMMENDATION

Item:

CS-10-145

File:

It is recommended to City Council:

Date of Report:

June 22,2010

Date of Meeting:

June 25,2010

Subject: Goodman Creek Stormwater Management Pond and Beaver Management Update

That report CS-10-145 dated June 22, 2010 titled "Goodman Creed Stormwater Management Pond and Beaver Management Update" be received for information.

Ward(s): 2 8 4

3.0 EXECUTIVE SUMMARY

N/A

4.0 INPUT FROM OTHER SOURCES

4.1 General

9 Engineering Services

9 Parks and ~nvironmental Services

9 Municipal Law Enforcement and Licensing

4.2 Auditor General

> The Auditor General has no comments.

Report to the Community Item: CS-10-145 Services Committee (Continued) - 2 - Meeting Date: June 25,2010

5.0 ANALYSIS

5.1 Background

9 In 1991 City Of Oshawa designed and built the Goodman Creek Stormwater Detention Pond to protect the downstream residential areas from flood hazards from the creek and from increased runoff from future urban growth. A map of the area is appended as Attachment #I

9 The area along Goodman Creek, south of King Street has experienced flooding in the past. See attachment #2

5.2 Beaver Management

9 In 2009, routine inspections of storm sewer outfalls conducted by Road Operations staff discovered higher than normal water levels in the Goodman Creek Stormwater Pond.

9 Further investigations revealed that beavers have constructed a dam, north of the earth embankment which is designed to store flood water, north of King Street causing a significant increase in water levels.

9 The increased water elevations resulted in an increased surface area in the detention pond and standing water in the storm sewer outfall from a nearby residential street.

9 Staff contracted a Ministry of Natural Resources (MNR) licensed trapper to remove the beavers before removing the dam and lowering the water.

9 Following public concerns and questions from Council, staff discontinued trapping and advised Council that additional professional assistance would be obtained to determine what further action was recommended.

5.3 Engineering and Wildlife Expert Recommendations

9 Staff engaged Water Resources and Environmental Engineer, Greck and Associates, and Wildlife Consultants, Beacon Environmental, both with specific expertise.in this area to assess the situation and provide professional advice and recommendations.

9 Greck and Associates conducted their review and provided a report including their conclusions and recommendations which are'appended as Attachment #3

9 The key conclusions and recommendations from the Greck report are:

Conclusions:

Report to the Community Item: CS-10-145 Services Committee (Continued) - 3 - Meeting Date: June 25,2010

a. The existence of the current beaver dam during a major storm event would increase peak storm flows, increase downstream flood elevations and reduce storage and discharge capacities

b. The risk of sudden failure of the beaver dam could worsen downstream flood hazards during a stom? event while potentially reducing downstream channel capacity causing flooding and erosion

c. Failure to remove the beaver dam could result in increase flood risks due to higher peak flows caused by the surge of water or the complete obstruction of the stormwater pond outlet

d. It is not likely that the existing earth berm can withstand the impacts of a permanent pool of water. If not adequately designed, seepage from a permanent pool could compromise the structural integrity of the berm over time

Recommendations:

a. The City should continue to operate and manage the Goodman Creek Stormwater Management Pond, as for the intended function of runoff quantity and quality control.

b. The existing beaver dam should be removed at the Goodman Creek pond for the following reasons:

i. To maintain the intended flood control functions of the Goodman Creek Stormwater pond, and

ii. To ensure reliable flood control functions and prevent unexpected peak flows due to blockage of the outlet or by the sudden failure of the beaver dam, and

iii. Manage the transport of excess debris to the downstream channel system

9 Beacon Environmental met with staff and assessed the site with respect to beaver management and other wildlife issues and provided a report with conclusions and recommendations appended as Attachment #4.

9 The key conclusions and recommendations of the Beacon report are:

> Should the City deem it necessary to remove the beaver dam for engineering reasons:

Conclusions':

a. The most opportune time to lower the pond water is within the CLOCA cold water timing window for in-water construction (July 1 to Sept 15).

Report to the Community Item: CS-10-145 Sewices Committee (Continued) - 4 - Meeting Date: June 25,2010

b. The dam should not be removed until after the breeding bird season as this could bring the City in contravention of the Migratory Birds Convention Act. This year and for the type of habitat involved, the'timing would be after July 30.

c. Removal of the dam without removal of the beavers is likely to be unsuccessful as they will likely immediately rebuild the dam.

Three options for beaver management were considered and evaluated as to which is the most humane or effective way to remove the beavers. .

a. Live trap and relocate over one km away.

b. Lethal trap at the dam.

c. Continuously break the dam and have the beavers try to rebuild until they finally give up and move up or downstream (which will pose problems in the new area).

= Recommendation:

It is recommended that the most ecological and also the most humane way to address the beavers was lethal trapping.

5.4 Next Steps

9 Based on the recommendations from the consultants, the City should be removing the beaver dam and restoring water levels to maintain the integrity of the stormwater management pond.

P Staff will retain a MNR licensed trapper to begin trapping the beavers in advance of July 31.

9 Respecting the recommended period for bird breeding, after July 31 staff will gradually dismantle the dam to lower the water level to minimize the impact to wildlife and the creek downstream, prior to the September 15 CLOCA deadline

6.0 FINANCIAL IMPLICATIONS

9 The cost to carry of the next steps outlined in this plan is estimated to be $5,000 and can be accommodated in the Community Services 2010 operating budget.

Report to the Community Item: CS-10-145 Sewices Committee (Continued) - 5 - Meeting Date: June 25,2010

7.0 RESPONSE TO THE COMMUNITY STRATEGIC PLAN

9 This report supports Goal C3 -Taking Action and Ensuring Accountability

Community services Department

LEBEND Q FLOODlN(3 AREA 0 BERM AREA - FLOODWE - CLOCA - . - - D ~ I M A G E - CLOGA CITY OF ~ ~ ~ W ! A -STORMSNVU~ DEPAR- OF CO-TY SERWGES

LEGEND - O&gW 64 8wndan

--- w d Flocd Une ~~ Flwd VuhsraMe Ana --- $00 Yesr Fl& Us

FIGURE 1: FLOOD VULNERABLE AREA DOWNSTREAM OF THE GOODMAN CREEK STORMWATER MANAGEMENT POND

City of Oshawa Goodman Creekstormwater Management Pond Beaver Dam Impact Assessment Study Page: 17

The following recommendations have be& prepared based on the findings of this study. The recommendations are based primarily on managing the flood risks associated with the intended

operation of the Goodman Creek Stormwater Management Pond and local storm sewer system

on Waverly Street North.

1. The City should continue to operate and manage the Goodman Creek Stormwater

Management Pond, as well as all other stormwater management facilities within the City for their intend functions of runoff quantity and quality control. The existing beaver

dam should be removed at the Goodman Creek pond for the following reasons:

a. To maintain the intended flood control functions of the Goodman Creek

Stormwater pond, and

b. To ensure reliable flood control functions and prevent unexpected peak flows

due to blockage of the outlet or by the sudden failure of the beaver dam.

c. Manage the transport of excess debris to the downstream channel system.

2. Notwithstanding Recommendation 1, there is an acceptable amount of risk to allow the

beaver dam to remain for the winter months. The City should maintain the permanent water elevation within the stormwater management pond resulting from the presence

of the existing beaver dam at an elevation of 105.5m, or less, based on a beaver dam

height of no more than 1.3 m relative to the upstream invert of the pond outlet pipe. This depth is approximately 0.23 m lower than the pond water elevation provided from

survey information used in this report. The minimal change in the water elevation will

help to reduce potential short term impacts to the natural environment within the pond

over the coming winter months.

3. The City should remove the two smaller beaver dams downstream of the pond outlet

structure to restore the original downstream flow capacity. The debris should be

removed off site or to a location where it will not be reintroduced into the channel

system.

4. Many existing and new stormwater management facilities are located throughout the

City which may experience similar impacts by beavers and similar concerns by local

residents. Therefore, the City of Oshawa should develop a plan or policy for the

GRECK AND ASSOCIATES LIMITED

City of Oshawa Goodman Creekstormwater Management Pond Beaver Dam ImpaRArsessment Study Page: 18

management of beavers including design features which may be used to discourage the

construction of beaver dams (e.g. beaver baffles or submerged outlets), the monitoring

of their ponds, and public education.

5. The pond depth in Recommendation 2 does not take into consideration the City's

requirements to manage stormwater management ponds for public safety during winter

months. The City has an existing policy to lower standing water levels in i t s stormwater

management ponds for public safety. Requirements related to public safety should take presentence over the presence of the beaver dam.

6. The City should conduct routine inspection of the pond and storm sewer outlet to

ensure it is free of debris and ice during the coming winter months.

7. This study has shown that downstream flood hazards are not significantly altered with a

minor reduction in flood storage and there is the potential to slightly lower downstream

flood risks with a reduced outlet opening. The use of a beaver dam to provide these benefits however is both unreliable and unstable in the long term. None the less the City of Oshawa should consider using the finding of this study and those reported in an

earlier study completed by Greck and Associates Limited (Greck 2002) to retrofit the

existing Goodman Creek Stormwater Management pond. This retrofit assessment may consider the creation of some form of permanent pond within the Goodman Creek

Stormwater Management facility to enhance and/or maintain some of the existing

environmental and social benefits which have evolved within this facility.

GRECK AND ASSOCIATES LIMITED

Item: CS-10-I& Attachment 4

b BEACON GUIDING SOLUTIONS IN THE NATURAL ENVIRONMENT

E N V I R O N M E N T A L

To: Craig Kelly, Bill Slute, Kevin Feagan, Phil Lyon, Patrick Lee, Gary Carroll, City of Oshawa

From: Brian Henshaw, Kim Baker, Beacon Environmental

Date: June 22,2010

Ref: 21 0047

Re: Beaver Activities at Goodman Pond, City of Oshawa

Over at least the past six years, activity by American Beaver (Castor canadensis) in the Goodman Pond, an on-line flood management facility in the City of Oshawa, has increased to a point where now the outflow has been dammed, raising the water levels in the basin.

As a result, a large pond has been created. This has converted the habitat from a seasonally flooded meadow marsh with cattails (Typha) and Reed Canary Grass (Phalaris arundinacea) and mostly a well-defined channel to a pond with open water, that in places is over 1 m deep (Photograph 1).

Temporary pond features, such as beaver ponds, tend to be very productive habitats. In urban areas this is especially true, as nutrients are also readily available. This allows a wide-range of flora and fauna to occupy these somewhat ephemeral wetlands. In urban areas, some urban-sensitive wildlife will be absent. However, many species will use urban beaver ponds, especially those located on watercourse systems, such as IS the case with Goodman Pond. The watercourse acts as movement corridor allowing access by a range of mammals, fish, amphibians and reptiles.

rnorograpn I : uooaman rona Apru ZUIU (nore Ganoe in OacKgrouna)

1 4 4 M a i n S t . N o r t h , S u i t e 2 0 6 , M a r k h a m , O n t a r i o , C a n a d a L 3 P 5 T 3 T e l : ( 9 0 5 ) 2 0 1 7 6 2 2 4. F a x : ( 905 ) 2 0 1 0 6 3 9

a BEACON June 22,2010

lNYIRONHIHi l l memorandum

Kev Biological Attributes of the Current Pond

Based on Beacon's experience with the location, observations made at the Goodman's Pond and habitat conditions, the key ecological attributes can be described as follows.

Fish habitat for a range of warmwater species Fish have been observed in many parts of the marsh. The area is therefore considered to be fish habitat under the federal Fisheries Act. It is also regulated by the Central Lake Ontario conservation Authority, both because it is a wetland and a watercourse. However, from an ecological perspective, the conservation authority is unlikely to be enthusiastic in supporting the maintenance of the pond as it represents a barrier to upstream fish movements and warms water, which could be detrimental to aquatic life downstream (if such sensitivities exist downstream, which they may not).

Waterfowl nesting opportunities This includes the nuisance Canada Goose (Branta canadensis) which nested at a high density in 2010 and Mallard (Anas platyrhynchos), a species that can use urban environments (Photograph 2). It is possible that other less tolerant species such as Blue-winged Teal will also nest in 2010.

Photograph 2: Nesting Mallard Atop a Large Muskrat House, Goodman Pond April 2010

s$ BEACON June 22,2010 E I V 1 R O N M E N T I I memorandum

Other Breeding Birds A wide range of other common wetland and edge habitat species are present in and around the marsh. it is possible that some less common wetland species may also be found. Some will be reliant on the existing water level. Dead and dying trees provide nesting opportunities for cavity nesters including Downy Woodpecker, White-breasted Nuthatch (Sitta carolinensis) and possibly Wood Duck (Aix sponsa) .

Foraging opportunities for other bird species Those requiring open water marsh, such as Belted Kingfisher (Ceryle alcyon) and Great Blue Heron (Ardea herodias) have been observed feeding. Interesting migrant waterfowl were also observed in 2010 including Hooded Mergansers and Green-winged Teal. This use is unusual and attests to the size and relatively undisturbed nature of the marsh, protected by woody vegetation and the size of the area, with limited public access.

Breeding habitat for amphibians and reptiles Species such as Green Frog (Rana clamitans), Leopard Frog (Rana pipiens) and American Toad (Bufo americanus) are breeding in the pond and will overwinter in deeper areas. The same applies to Midland Painted Turtle.

Mammals In addition to the single large beaver lodge and the dam, there is habitat for other wetland-dependent species such as Muskrat (Ondatra zibethicus). There were more Muskrat houses here in the spring of 2010 than in the entire area of Oshawa Second Marsh. It is possible that food resources will be depleted for this species. However, a predator of the Muskrat, the Mink is also now resident at the pond. Other species also occur in the area such as Red Fox (Vulpes vupes).

In summary the Goodman Pond is providing a boost to local biodiversity, one that is likely to be limited in time. Often conservation organisations manipulate water levels over cycles of five or seven years to replicate this effect that is typical ofbeaver activity. The ecological attributes of the pond do not the reach the test of,provincial importance, but at the local scale it does support unusually high biological diversity (for an urban area) at least until the beavers exhaust the local food supply. This is occurring in' an area where residents of Oshawa can enjoy the wildlife and it is likely that they will have an opinion on future management options. Some of the ecological negatives, such as increasind Canada Goose nesting opportunities can be managed by the City.

O~tions for Beaver Manaaement

Without considering issues of human safety, there are three options for managing the beavers at Goodman Pond. These are discussed in the following paragraphs.

1. Beaver Baffle The installation of a beaver baffle would enable the water levels to be managed, such that they could be set at the upper operational limit for the pond, as determined by City staff. The baffle works by regulating the water level by dispersing the excess water through a pipe or pipes

Page 3

@ BEACON I I I V I R O N U I N T A L

June 22,2010

memorandum

installed on an angle through the dam and held in place by stakes driven into the ground. The upper end of the pipe in the pond should be covered with screening so the pipe does not get plugged with vegetation. Using metal mesh fencing, enclose the outlet so that beavers cannot get at the outflow. This will require regular maintenance as the beavers are adept at solving baffles of almost all kinds.

The baffle should be installed during the early fall to minimize d~sturbance to the beavers and other wildlife. The water level should remain a minimum of 1 - 1.2 metres deep in the autumn and winter to ensure enough depth to prevent freezing to the bottom of the pond. Even then there will be some risk of freezing out the beavers in a hard winter. Water levels should not be substantively reduced prior to August 10 to ensure that breeding birds are protected. The disturbance of nesting birds is not permitted under the Migratory Birds Convention Act. Fines under the federal Act are substantive. Although seldom enforced, this Act protects birds, their nests and eggs from disturbance, harassment, killing etc.

2. Dam Removal The beaver dam could be removed from the pond to allow the water level to return to the pre- beaver activity level. Prior to removing the dam, the beavers should be live-trapped or lethal trapped from the pond and (if live-trapped) relocated elsewhere. Professional trappers in Durham Region could be retained to provide these services. Note that there are probably five or six beavers present and that live-trapping is a difficult and expensive exercise and needs to be conducted in summer if animals are to be relocated. If lethal trapping is used this could be accomplished later in the fall, but priorto freeze-up to facilitate dam removal.

Wpile live trapping is an option it is expensive, difficult to undertake and can fail. The large heavy. traps are around $500 and easily stolen or interfered with; in most cases they need constant surveillance; they are heavy they could injure a child or pet. Trappers sometimes do not like to attempt live trapping. With a large beaver inside it may take two persons to carry the trap. In particular, the beavers become very wary once one has been trapped and removed and there may be as many as six to trap. Beavers would also have to be relocated outside the watershed or they may return. In their new location, they may have trouble establishing a lodge and winter stores.

To minimize the impact of removing the beavers and to other wildlife using the pond, the beavers would be trapped in late summer (or fall if lethally trapped) and the dam removed immediately thereafter. In any event the dam should not be removed prior to August 10 to ensure that breeding birds have finished using the wetland, or after early October to avoid killing hibernating animals. The residual dam removal period is August 10 to October 10. The conservation authority should be consulted prior to dam removal. If the animals are removed, for other wildlife species like amphibians and reptiles we would favour a more gradual lowering of the water level, but this would only work once the beavers have been removed.

Removal of the dam without removal of the beavers is likely to be unsuccessful as they will likely immediately rebuild the dam. We have not seen a successful incremental lowering of a dam until the beavers simply give up and move on. In addition this might be less humane than either relocation or lethal control.

BEACON June 22,2010 E N V I R O W M I N T A I memorandum

3. Do Nothing If no action was taken and the beavers were left alone, the pond and its htgh water levels would be maintained (presumably, the City would still seek to establish an upper operating level). On-going beaver activity would likely result in the loss of many of the trees within the pond area. Over time, there could be an increase in the amount and diversity of wildlife using the pond for breeding and foraging (and possibly resting during migration) followed by a decline in productivity.

However, the beaver activity would likely continue only for two to three years until they run out of food supply. As there is a finite amount of trees within the pond area, they have a limited amount of food, with poplars and willow being their preferred items. There is little to no opportunity. for the beavers to expand their feeding range beyond the pond. There may be future complaints from residences as beavers seek food supplies in yards.

Most likely a combination of food supply limitations andlor'a hard freeze during the winter, will result in the beavers vacating the pond within the next three years.

Next S t e ~ s

The City of Oshawa should weigh the risk factors related to.flooding and human safety against the ecological and social benefits that the beavers have created. As with all safety issues risk management will be a key determinant, as many activities thai humans undertake are Inherently unsafe (flying for example).

If the City determines that the beavers must be removed then lethal trapping is the most effective and possibly also the most humane way to address the beavers. Given that thousands are lethally trapped every year in Canada, this would be the preferred method. It should be carried out only by a licensed trapper who has experience in removing urban beavers and is sensitive to the situation.

The City might also consider developing a standard approach to beaver management, and incorporating other urban wildlife management areas such as goose management, in such a document.

Brian E. Henshaw Principal