Ministry of Water, Land and Air Protection - Lorin Lake Bridge 8200 Road

Lorin Lake Bridge 8200 Road

Objectives

The primary objective of this project was to remove man-made barriers to fish passage allowing migrating fish access to increased habitat. A second objective was to reduce the risk of sediment delivery into the stream.

FRBC Region/ MELP Region/ MoF Region

Cariboo-Chilcotin/Cariboo/Cariboo

Author

Ken MacKenzie

Proponent

Weldwood of Canada Ltd.

100 Mile House Operations

Location:

The crossing is located at 14.5 km on the Bowers Lake Forest Service Road (8200 Road) at an unnamed stream which flows from Lorin Lake into Cougar Creek.

Introduction

Both Lorin Lake and Cougar Lake are popular fishing lakes and receive moderate to high fishing pressure throughout the fishing season. Rainbow trout are the only game fish found in this system.

Assessments and Prescriptions

The Jim-Windy Watershed fish passage – culvert inspection report identified this site as the top priority for restoration in this watershed for a number of reasons. The culvert at the crossing was a complete barrier to fish passage by increasing water velocity (velocity on June 6, 1998 was 1.81 m/s) and because of an outfall drop of 25 cm. The stream has good potential spawning substrate and is the main upstream tributary for Cougar Lake. The culvert was undersized and had the potential to become plugged which may have resulted in a serious road washout and considerable sediment delivery into the stream.

Because of the relatively steep slope of the stream at the crossing site (6.5%), the best option to restore fish passage was deemed to be a clear-span structure. A permanent, concrete decked bridge was prescribed because the Bowers Lake FSR is a well used main haul road.

Rehabilitation Work

To minimize environmental impacts during the culvert replacement work, the following steps were taken:

Flow was blocked into the culvert using rock and filter fabric so that all work was performed in a dry environment.
Water was pumped around the culvert into the plunge pool at the outfall using fire-fighting water pumps during installation.
Water was pumped into barrels to reduce water velocities to prevent scour and sediment generation in the stream.
Sediment traps of hay bales and filter cloth were installed downstream of the pump discharge.
An environmental monitor was on site for all phases of construction

Structure Details

9.1 meter concrete deck composite design (fig. 1-2).
pre-cast concrete footing with 8 inch steel towers.
bridge deck at 3% slope.
reconstructed channel width 2.5 meters.

Cost Summary

Design, supply and install bridge $47,500

Rip rap supply $2,500

Supervision $2,000

TOTAL $52,000

Environmental Benefits

Rainbow trout from Cougar Lake now have unrestricted access to an additional 1.5 km of spawning stream to Lorin Lake in addition to Lorin Lake itself and the small streams that drain into it . This more than doubles the available upstream habitat from Cougar Lake. The trout population in Lorin Lake is no longer isolated from the remainder of the watershed.

For Further Information Contact:

Ken MacKenzie
P.O. Box 97
Weldwood of Canada Ltd.
100 Mile House Operations
100 Mile House, BC
V0K 2E0
Tel. (250)395-8280

Figure 1-1. Channel is constructed to route stream prior to pulling culvert on unnamed creek.

Figure 1-1. Channel is constructed to route stream prior to pulling culvert on unnamed creek.

Figure 1-2. Completed 8200 road bridge installation.

Figure 1-2. Completed 8200 road bridge installation.