rock creek gold creek risk analysis and prescriptions final · pdf fileadams lake anglemont...

2006 FIA

Gold Creek / Rock Creek Inspections Monitoring, Road Deactivation

and Environmental Road Maintenance Planning Risk Analysis

Prepared for:

Prepared by:

Forsite Consultants Ltd. #330 42nd St SW Salmon Arm, BC

V1E 4R1

Tel: (250) 832 3366 Fax: (250) 832 3811

October 31st, 2006

Adams Lake Lumber FCL File: 1-66 Inspections Monitoring, Road Deactivation and Environmental Road Maintenance Planning Risk Analysis October 2006

S:\1\66\Current\Documents\Reports\Rock Creek Gold Creek Risk Analysis and Prescriptions FINAL.doc

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Table of Contents

TABLE OF CONTENTS ..................................................................................................................................................II

1.0 INTRODUCTION .................................................................................................................................................4

1.1 SCOPE OF ASSESSMENT ........................................................................................................................................4 1.2 CONVENTIONS FOLLOWED ...................................................................................................................................4

2.0 OFFICE AND FIELD REVIEW..........................................................................................................................5

3.0 TERRAIN CHARACTERISTICS AND GEOMORPHOLOGICAL PROCESSES.......................................7

4.0 RISK ANALYSIS PROCEDURE ........................................................................................................................7

5.0 OBSERVATIONS ANALYSIS AND RECOMMENDATIONS .......................................................................8

5.1 GOLD CREEK – SITE A (REACH 0139) ..................................................................................................................8 5.2 GOLD CREEK – SITE B (REACH 2902) ................................................................................................................11 5.3 GOLD CREEK – REACH 0106 ..............................................................................................................................14 5.4 GOLD CREEK – REACH 0134 / 7902 ...................................................................................................................15 5.5 GOLD CREEK – REACH 1901 ..............................................................................................................................18 5.6 GOLD CREEK – REACH 3801 ..............................................................................................................................19 5.7 GOLD CREEK – REACH 4700 / 4601 ...................................................................................................................21 5.8 GOLD CREEK – REACH 6402 ..............................................................................................................................23 5.9 GOLD CREEK – REACH 6207 / 6208 ...................................................................................................................26 5.10 GOLD CREEK – REACH 7001 ..............................................................................................................................28 5.11 GOLD CREEK – REACH 7203 ..............................................................................................................................30 5.12 GOLD CREEK – REACH 7205 ..............................................................................................................................31 5.13 GOLD CREEK – REACH 7604 ..............................................................................................................................32 5.14 GOLD CREEK – SITE 1 ........................................................................................................................................34 5.15 GOLD CREEK – SITE 7 ........................................................................................................................................35 5.16 GOLD CREEK – SITE 8 ........................................................................................................................................37 5.17 GOLD CREEK – SITE 9 / 10..................................................................................................................................39 5.18 ROCK CREEK – SITE 1 ........................................................................................................................................41 5.19 ROCK CREEK – SITE 2 ........................................................................................................................................43 5.20 ROCK CREEK – SITE 3 ........................................................................................................................................45 5.21 ROCK CREEK – SITE 4 ........................................................................................................................................47 5.22 ROCK CREEK – SITE 5 ........................................................................................................................................48 5.23 ROCK CREEK – SITE 6 ........................................................................................................................................50 5.24 ROCK CREEK – SITE 7 ........................................................................................................................................52 5.25 ROCK CREEK – SITE 8 ........................................................................................................................................53 5.26 ROCK CREEK – SITE 9 ........................................................................................................................................54 5.27 ROCK CREEK – SITE 10 ......................................................................................................................................56 5.28 ROCK CREEK – SITE 11 ......................................................................................................................................58 5.29 ROCK CREEK – SITE 12 ......................................................................................................................................63 5.30 ROCK CREEK – SITE 13 ......................................................................................................................................65 5.X ROCK CREEK – SITE 14 ......................................................................................................................................66 5.31 MOSQUITO CREEK (SITE 1) ................................................................................................................................67 5.32 HONEYMOON BAY (SITE 2) ................................................................................................................................71 5.33 MOMICH LAKE SITE 3 ........................................................................................................................................75 5.34 MOMICH LAKE SITE 5 ........................................................................................................................................77

6.0 CLOSURE............................................................................................................................................................78



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LIST OF FIGURES

Figure 1 Location Key Map……………………………………………………………..6

Figure 2 Gold Creek Sites……………...…………………………………….……….…attached

Figure 3 Rock Creek Sites..………………………………………….……….……….…attached

Figure 4 Site 0139 detail……………………………………………..…………………..10

Figure 5 Site R-9, Branch D Road detail………………………………………….……..55

Figure 6 Site R-11, “Branch C” Road detail ……………………..……………….……..62

Figure 7 Mosquito Creek Site 1 detail…………………………………………………...70



1.0 Introduction

Forsite Consultants Ltd. (Forsite) was retained to carry out post work inspections, monitoring and prescriptions

for sites in the Rock Creek, Gold Creek, Mosquito Creek, Marjory Creek and Momich Watersheds. (see figure

1 for a key map).These sites have had previous work and/or inspections completed. The objective of this

report is to address remaining concerns and to establish closure on these sites.

1.1 Scope of Assessment

The purpose of this report is:

• To describe conditions at specific assessment sites and where such conditions may have a specific

impact.

• To provide a Risk Analysis of the potential environmental impacts of the assessment sites

• To recommend site-specific actions to reduce the likelihood of further environmental impacts.

1.2 Conventions Followed

• Soil classifications and landform descriptions use terminology defined in the publication Terrain

Classification System for British Columbia B.C. Ministry of Environment 1997.

• Slope gradient classification follows the convention defined in the publication Terrain Classification

System for British Columbia B.C. Ministry of Environment 1997.

Gentle 5-27%

Moderate 28-49%

Moderately Steep 50-70%

Steep > 70%



2.0 Office and Field Review

Prior to and following the field assessment the following materials were reviewed:

• Stereo air photo coverage of the study area (~1:20,000 scale)

• 1:20,000 digital design file maps

• Geologic Survey of Canada Bedrock Geology Mapping located on Ministry of Energy and Mines

MapPlace webpage http://webmap.em.gov.bc.ca/mapplace/minpot/bcgs.cfm

Gold Creek

• Level 2 Fish Habitat Assessment (Silvatech 1995)

• Level 2 Road Condition Assessment 9silvatech 1996)

• Detailed Proposal – Zone 1 and 2 Works Phase (Silvatech 1996)

• Level 2 Stream Channel Assessment (Silvatech 1998)

• Bioengineering as-builts (Silvatech 1998)

• Watershed Restoration Plan (Silvatech 2001)

• Road Assessment 9Silvatech 2004)

Fieldwork was completed by Peter Weisinger M.Sc. GIT of Forsite on August 14, 15th and 18th-19

th 2006. See

Figure 2 for a map of the study area and location of the assessment sites.

A helicopter over-flight of the Gold Creek sites was completed on August 11th 2006. Attending were Peter

Weisinger M.Sc. GIT and Rod Williams P.Geo of Forsite. The helicopter overflight focussed primarily on

previously identified sites, but observations of general watershed condition and sediment sources and other

potential problem areas were noted.

Rock Creek

• Environmental Maintenance Project Plan (Summit 2003)

• Road Assessment (2004)

• Environmental Maintenance Projects (Mosquito, Honeymoon, Marjory)

Fieldwork was completed by Peter Weisinger M.Sc. GIT of Forsite on August 1-4th, See Figure 3 for a map of

the study area and location of the assessment sites. Additional field review of the Rock Creek site R11 was

conducted on October 20, 2006.



Adams Lake

Anglemont

Annis

Balmoral

Birch Island

Blind Bay

Blucher Hall

Celista Eagle Bay

Lee Creek

Magna Bay

Notch Hill

Scotch Creek

Seymour Arm

Sicamous

Solsqua

Sorrento Squilax

St. Ives

Sun Peaks

Vavenby

Figure 1 – Key Map

Gold Creek Sites (Figure 2)

Rock Creek Sites (Figure 3)

Rock Creek

Honeymoon Bay Momich Lake

Mosquito Creek

Gold Creek



3.0 Terrain Characteristics and Geomorphological Processes

3.1 Rock Creek / North Adams Lake Sites

The sites in the Rock Creek area are generally located either in the valley bottoms, or on mid slopes. Soils

encountered were generally either sandy tills or sandy glaciofluvial and fluvial materials. These soils wee

found to have low cohesion and were easily eroded. The upper portion of Rock Creek is on a wet rolling

plateau, with the creek becoming incised in its lower reaches. Instability in this area was generally limited to

sediment production due to drainage diversions as a result of road construction. In the incised lower draw,

drainage diversions leading to gentle over step types of landslides were found to be of concern.

3.1 Gold Creek Watershed

The sites in Gold Creek are located primarily on the Adams Plateau. Soils encountered ranged from sandy

glaciofluvial materials in draws and in the Gold Creek Draw, to weathered colluvial rubble and tills on the flat

upland areas. The sides of the Gold Creek watershed are steep, with significant relief. Gentle-over-steep types

of failures are associated with a number of these sites, and pose the highest hazard. Concerns were primarily

drainage diversions which had led to instability downslope, or were directly related to minor sediment

production adjacent to streams.

4.0 Risk Analysis Procedure

This report provides a qualitative evaluation of hazards associated with sites previously identified in the study

area, a description of the potential consequences, and recommendations to reduce the hazards and associated

risks. Acceptance of the qualitative consequence values and the subsequent risk analysis is the responsibility

of the licensee or the regulatory authority, as is the determination of acceptable risk and the decision to proceed

with any action based on that risk analysis.

Consequence ratings have been estimated based on standard practice and identification of downslope resources

in the area. The main streams in the study area (Gold Creek and Rock Creek) are fish bearing. Sediment

delivery to a fish stream is considered a moderate to high consequence dependent on the magnitude of the

hazard and location of the identified site in relation to the stream.



5.0 Observations, Analysis and Recommendations

5.1 Gold Creek – Site A (Reach 0139)

Location: Gold Creek Reach 1039,

Map Reference: G-0139

Previously identified issues: The old road location was constructed across a slide with sediment from road surface and fillslope eroding,

depositing material in the stream. (Silvatech 1998)

Restoration undertaken: The road has been relocated and the original road deactivated. The portion of road adjacent the slide area has

been recontoured and grass seeded as per ‘Option A’ in the Silvatech (1998) Report. The remainder of the

road has been deactivated through cross ditching.

Observations: The road section located directly downslope of the slide area is experiencing some streambank erosion (see

photo plates 5.1.1 and 5.1.2.) Although grass seeding has been successful on the open slopes reducing surface

erosion, lateral erosion of the streambank is continuing, with sediment mobilising events likely occurring

during periods of peak flow. The channel appears to be migrating laterally towards the former road location,

being confined by bedrock on the opposite (right) side. Severity of erosion has decreased since remediation

measures have been implemented.

Risk Analysis: There is judged to be a high likelihood of sloughing of road fill materials and ongoing delivery (with peak /

seasonal flows) of sediment to Gold Creek at this site, on the order of 1-2m3 annually. This is considered a

moderate consequence. The risk is therefore high.

Prescription:

• Place large diameter Rip Rap along ravelling cut bank to slow lateral stream erosion

• Revegetate with deciduous species adjacent to stream.

• Plant coniferous species on rehabilitated road surface and on old slide area



Photo 5.1.1 – Aerial view of Reach 0139

Photo 5.1.2 – Eroding streambank Reach 0139



Figure 4 – Site 0139 detail



5.2 Gold Creek – Site B (Reach 2902)

Location: Gold Creek, Reach 2902,


Previously identified issues Fillslope failure and unstable cutslopes in fine grained soils contributing sediment to stream (Silvatech 1998).

Restoration undertaken Road has been relocated, old road pulled back and hydroseeded / bio-engineered.

Observations The road has been bypassed, and the site has been fully recontoured. Grass seeding was partially successful,

having taken on the recontoured road, though not on the upper portion of old cutslopes (Photo plate 5.2.1).

Bio-remediation attempts were unsuccessful (Photo 5.2.3) and the site has not yet revegetated. The former

bridge (log box?) at the stream crossing has been removed, though cribbing was left in place. The stream

appears to be stable. Only minor amounts of sediment from the old road location appears currently to be

entering the stream at high streamflows, where some material may be entrained at the crossing.

Risk Analysis There is judged to be a moderate likelihood of sediment producing events (small surficial slides, rilling) at

this site. This would result in a small amount (< 5m3) of material mobilised at the stream crossing during a

peak flow event and from small erosional events on the unvegetated upper cutslope. This would be considered

a low consequence. The risk is therefore low.

Prescription

• Bioengineering of slopes recommended to further stabilise the area as per (Silvatech 1998) Report.

• Consider planting area with coniferous species

• Hand grass seed the remaining open slopes



Photo 5.2.1 – Deactivated road at reach 2902

Photo 5.2.2 – Wooden cribbing left in place, minor sloughing of old road fill.



Photo 5.2.3 – Evidence of unsuccessful bio-remediation.



5.3 Gold Creek – Reach 0106

Location: Gold Creek, Reach 0106


Previously identified issues Severely aggraded active channel, deposition area/ sediment wedge above bedrock constriction.

Restoration undertaken None reported. Previous prescriptions suggest monitoring and controlling sediment input from upstream.

Observations The stream is heavily aggrading, with multiple channels and significant lateral movement where the channel is

not confined by bedrock. Numerous log jams were noted along this reach. There is no sign of direct

connectivity to the road system. Problems in this area are symptomatic of overall hydrologic conditions in the

watershed.

Risk Analysis No risk analysis was performed at this site. A risk analysis for this reach would be a function of hydrology of

entire watershed, which is beyond the scope of this study.

Prescription

• Continue to monitor drainage issues in the watershed / control sediment sources in previously

developed areas.

Photo 5.3.1 – Aerial view of reach 0106 showing severe aggradation.



5.4 Gold Creek – Reach 0134 / 7902

Location: 523-100 Road [~2.5 km]


Field Identification: ∆206-∆221

Previously identified issues A spur road has diverted flows from upslope leading to slope failures below (Silvatech 1998).

Restoration undertaken Natural drainage patterns have been restored, spur and branch roads deactivated.

Observations The upper spur road has been thoroughly deactivated with numerous cross drains. The natural flow of the

main drainage path has been restored. Large cross ditches effectively prevent further diversion on the upper

spur road. Some intercepted small flows on the upper spur have been diverted to cross drain culverts on the

100 Road. The crossing at the upper road is well armoured, with some very minor sediment input from

ravelling road fills. Some drainage intercepted by lower road and 600CMP at ∆218. There is evidence of

previously large flows in the ditchline on the lower road. The lower stream crossing at ∆220 is eroding some

fill material.

Aerial observations – the slide has partially naturally revegetated. The site is likely still a significant sediment

source as it is adjacent to Gold Creek. Bio-engineering and seeding should be carried out as per the

prescription in Silvatech (1998) report.

Risk Analysis As the natural drainage patterns have been restored, there is judged to be a low likelihood of initiating another

large landslide which could impact Gold Creek at this site. Such a slide would result from drainage diversion

and concentration in a ‘gentle over steep’ type of scenario as happened with the previous slide. This would

result in significant input of sediment to Gold Creek, and result in long-term sediment source production. This

is considered a high consequence. The risk is therefore moderate

There is a moderate to high likelihood of further sediment mobilisation on the old slide path, with sediment

delivery of <25m3 to Gold Creek. This would result in input of a small to moderate (to 25m

3) amount of

sediment to Gold Creek, which would be considered a moderate to high consequence. The risk is therefore

moderate to high.

Prescription

• If the 100 Road is to continue to remain operational, monitor exiting culverts and restoration efforts on

the road to ensure continued functioning. If no future use of the road is anticipated, permanent

deactivation should be considered (i.e. pull all culverts)

• Revegetate slide as per Silvatech (1998) bioremediation prescription.



Photo 5.4.1 – ∆220 Stream crossing



Photo 5.4.2 – Lower portion of slide entering Gold Creek




Location: Tributary 250m upslope of Reach 1901 of Gold Creek


Previously identified issues Collapsed bridge on old road has diverted flows south along road, through forested area and into Gold Creek.

Deposition of materials in forested area.

Restoration undertaken Collapsed culvert has been removed, berm constructed and planted with dogwood.

Observations Observation from helicopter overflight revealed no further disturbance of tributary channel.

Risk Analysis There is judged to be a low likelihood of a future breach of the stream channel as a result of the old road

location, which could result in minor sediment deposition into gold Creek. This is considered a moderate

consequence. The risk is therefore low.

Prescription

• None required




Location: Gold Creek Reach 3801,


Field Identification: ∆203

Previously identified issues Large log jam/pile at bottom of slide, perched fills at deactivated road crossing (∆203).

Restoration undertaken Road crossing has been deactivated. Upper road at initiation point of failure has been deactivated.

Observations Crossing at lower road still has some minor perched fills present, though the crossing has been sloped back and

rehabilitated. Current flow is crossing over old road surface in a ‘self-armoured’ channel – no sign of recent

disturbance. Road surface is revegetating (grass seeding effective). Some perched fills are still present but

most material appears to have been pulled back in critical areas. Sediment mobilisation is not likely to be a

catastrophic failure but rather a progressive erosion of fill materials.

Risk Analysis There is judged to be a moderate likelihood of a mobilisation of

road fill materials, resulting in transport of

fine sediment (<5m3) to the tributary of Gold Creek. This is considered a low consequence. The risk is

therefore low.

Prescription

� No further work required / continue to monitor



Photo 5.6.1 – Stream crossing old road.




Location: Road upslope of Reach 4700, and bridge crossing of Reach 4601

Map Reference: G-4700 / G-4601


Previously identified issues Creek diverted by old skid trail and mainline. Failure 300m below mainline and channelized debris flow into

Gold Creek.

Restoration undertaken Natural drainage was restored on mainline, 500mm culvert installed. Failure was grass seeded.

Observations The slide headwall and main portion of the slide is revegatating and appears to be stabilising – some sidewall

failures are taking place on the channelized portion of the slide. Some coniferous vegetation is starting to re-

establish. Material had been scoured to bedrock in track of the slide, and remobilisation is unlikely. On the

eastern side of the headwall, there is significant flow emanating at the base, with soil materials perched

upslope. There remains the possibility that further headward erosion will continue. The area upslope of the

slide (∆121) and to the south of the main slide have a number of old revegetated slide scarps present.

At ∆122, the road cuts through a rock outcrop, and as a result the ditchline is very shallow and prone to

overflowing onto the road. Evidence of water flow downslope suggests that this may be a point at which some

water had previously been diverted to the slide. The drainage diversions identified in the Silvatech 1998 report

have been restored.

Risk Analysis Drainage diversions upslope have been repaired, however natural drainage is seeping from the headwall of the

scarp. There is judged to be a low to moderate likelihood of further sliding of material at the landslide site,

resulting in delivery of <25m3 of material to the reach and a moderate likelihood of delivery to Gold Creek.

This is considered a moderate consequence. The risk is therefore low to moderate.

Prescription

• Monitor and maintain ditchline on road / Improve ditchline through ∆117

• Allow slide area to revegetate naturally.



Photo 5.7.1 – View up headwall of slide

Photo 5.7.2 – View down slide path




Location: Spur in Block 81-1


Field Identification: ∆124-128

Previously identified issues Stream diverted by skid trail.

Restoration undertaken Stream restored to original channel. Roads and trails deactivated.

Observations The point of diversion by the old skid trail has been restored and the stream is now flowing in what appears to

be the original channel. The diversion has been blocked by a vegetated berm, however water is seeping

through this berm and still flowing down the skid trail. There is a low to moderate likelihood that a large

streamflow could ovetop the structure and again be diverted by the skid trail. In some areas the skid trail is at a

lower elevation than the natural stream draw. ∆128 is a low point on the trail.

Some seepage is emanating on the road at ∆124. This appears to be an area where some of the stream flow is

diverted, primarily as subsurface flows, to the road. There is no cross drain structure here, and water flows

down the ditch to pond on the high side of the road at the junction of the deactivated road downslope, resulting

in wet road conditions. There is a 400mm CMP which takes the flow at ∆126 across the mainline.

Risk Analysis There is judged to be a low to moderate likelihood of a stream avulsion at the previous point of diversion,

resulting in flows being diverted down the skid trail, entrainment of fine materials at the road crossing and

subsequent delivery to the stream system to the north. This would also result in the loss of a small amount of

productive area. This is considered a low to moderate consequence. The risk is therefore low to moderate.

Prescription

• Upgrade berm by hand, increasing height by ~0.3m, and width by about 1m, with locally available

rock.

• Monitor berm on skid trail for future avulsions.

• Improve ditchline to ∆126 (400mm CMP), clean sump.



Photo 5.8.1 – Aerial view of site

Photo 5.8.2 – ∆124 seepage onto road

Diverted stream flow along skid trail and ditchline

Natural stream channel



Photo 5.8.3 – ∆127 There is still some minor drainage along the old skid trail (left).

(photo taken from top of berm.)




Location: Block 81-1

Map Reference: G-6207 / G-6208


Previously identified issues: (6207) Stream diverted by skid trail, no riparian buffer maintained through block.

(6208)Stream diverted by skid trail causing ‘twin channels’. Poorly defined channel at mainline crossing, some

flows follow ditch south.

Restoration undertaken (6207) Stream restored to original channel, roads and trails deactivated.

(6208) Culvert entrance and ditch grading improved, channel definition improved near culvert

Observations Streams have been restored to original flows. Skid trail that had been an issue on 6207 is revegetating.

Culvert functioning well.

Risk Analysis There is judged to be a low to negligible likelihood of further diversions at these two sites.

Prescription

• No further works required

Photo 5.9.1 – Culvert 6208



Photo 5.9.2 – Reach 6208




Location: Reach 7001



Previously identified issues Creek was temporarily diverted by skid trail, deposition at culvert inlet.

Restoration undertaken Creek restored to natural channel, inlet cleaned.

Observations The point of diversion was repaired, the stream appears to currently be taking about 90% of the flow. There is

still some minor diversion taking place along the old skid trail. Diverted flow returns to channel downstream.

Risk Analysis There is judged to be a low likelihood of recurrence of a stream avulsion at this site. This would resulting in

streamflow being diverted by the skid trail with some minor sediment entrainment. Sediment is not likely to

reach a fish bearing stream. This is considered a low consequence. The risk is therefore low.

Prescription Potential disturbance by machine likely to be more disruptive than leaving the site undisturbed. Restoration

(cross-ditching) could be conducted by hand, however the majority of the flow is likely to stay in the natural

channel.

• Cross drain flow on trail back to stream draw by hand.

• Install wide shallow swale (culvert backup) at stream crossing ∆130.



Photo 5.10.1– Stream looking towards road. Direction of diversion along old skid trail indicated.




Location: Road in Block 509-2



Previously identified issues Streams had been diverted by skid trails in the block, culverts washed out, deposition downstream.

Restoration undertaken Diversions have been restored by hand, road deactivated.

Observations Streams at road crossing have stabilised, and are well incised. Swales at stream crossing are revegetating.

There is some minor lateral erosion of road fill materials at crossings, but this is expected to decrease as

riparian vegetation re-establishes.

Risk Analysis There is judged to be a low to negligible likelihood of mobilising sufficient sediment to impact a fish bearing

reach of the Gold Creek from this site.

Prescription

• No works required

Photo 5.11.1 – Stream crossing reach 7203




Location: Reach 7205 at road crossing


Previously identified issues Creek diverted by skid trails, hazard of diversion along mainline.

Restoration undertaken Channel restored, culvert improved.

Observations Deflector berm and culvert have been upgraded – no issues at crossing.

Risk Analysis There is judged to be a low to negligible likelihood of mobilising sufficient sediment to impact a fish bearing

stream from this site.

Prescription

• No further works required.

Photo 5.12.1 – Reach 7205 at road crossing




Location: Reach 604 in Block 523-2



Previously identified issues No riparian buffer in block, slash in streams, blocked and damaged culvert.

Restoration undertaken None

Observations 600mm CMP in place, functioning. There is evidence of significant flows in this draw. Riparian area well

vegetated and regrowing. Soils in this area are rocky and free draining. No immediate concerns as long as

culvert remains functional.

Risk Analysis Given the past history of plugging, and evidence of significant seasonal flows in this stream, there is a

moderate likelihood that this culvert will become plugged or fail, leading to a washout of the road and

subsequent sediment delivery to the stream system. There is a moderate likelihood of material being delivered

downstream to Gold Creek. This would be considered a moderate consequence. The risk is therefore

moderate.

Prescription

• Pull culvert / construct broad armoured swale with planned road deactivation, or install failsafe cross

ditch as per Silvatech (1998) prescription.

Photo 5.13.1 – Crossing at Reach 7604



Photo 5.13.2 – 600 mm CMP at Reach 7604 crossing



5.14 Gold Creek – Site 1


Map Reference: G-1


Previously identified issues Damaged and blocked 300mm culvert, road requires deactivation. (Silvatech 2004)


Observations Crushed and mangled culvert still in place. There is evidence of significant ditch flow in the past (foreground

in photo). The culvert is at a low point in the road, with ponding water on the high side.

Risk Analysis This site is on flat to gently sloping plateau. There is judged to be a low to negligible likelihood that

significant drainage diversion could take place at this site.

Prescription

• Remove culvert and install cross ditch. This can be done with deactivation on the remainder of the

road.

Photo 5.14.1 – Crushed culvert.





Map Reference: G-7


Previously identified issues Deck material rotting, but crib wall and stringers look in good shape. (Silvatech 2004)


Observations Deck on the bridge is rotting out. There has been a small slide to the northwest of the bridge in the road cut

(see photo 5.15.1). No significant amount of debris has entered the stream as a result, however several trees

have been uprooted and are threatening to fall onto the bridge deck / upstream of the bridge which may result

in a temporary blockage.

The cribbing on the downstream side of the town side approach is beginning to erode. The stream gradient

downslope is 80% for about 7m immediately after the crossing. A blockage / collapse of the structure may lead

to alteration of flow and/or significant erosion of the stream bed and / or mobilisation of debris downslope.

The bridge could likely be left in place for some time before significant problems arise, however a high flow

event or mass movement event in the channel may accelerate deterioration and lead to significant sediment

input.

Note: Reach 4700 is located upslope of this bridge. There is no evidence of the debris flow reaching this

location.

Risk Analysis There is judged to be a low likelihood of a structural failure on this bride (cribbing collapse / creek blockage)

within the next 20 years that could result in significant sediment delivery to Gold Creek. This is considered a

high consequence. The risk is therefore moderate.

Prescription

• Bridge superstructure and cribbing should be removed, and approaches sloped back and revegetated.

• Pull back all materials adjacent the creek to create a broad swale, and armour stream crossing with

coarse rock

• Remove material slumping into creek at road cut

• Supervision of deactivation works by a qualified registered professional is recommended.



Photo 5.15.1 – Log Bridge, ∆201 (Silvatech 1998 “Site 7”)

Photo 5.15.2 – Log Bridge, ∆201 (Silvatech 1998 “Site 7”) SE corner of Cribbing starting to collapse.




Location: Bridge at crossing between blocks 522-2 and 522-3

Map Reference: G-8


Previously identified issues Bridge, “Site 8”. No significant issues identified – guardrails were beginning to rot. Silvatech (1998)


Observations Bridge is showing significant rot, but no sign of imminent collapse. Bridge will likely remain intact for a

number of years, but continued degradation will compromise load bearing capacity.

Risk Analysis There is judged to be a low likelihood of a structural failure on this bridge that would result in delivery of a

small to moderate amount of sediment to the stream, considered a low to moderate consequence. The risk is

therefore low.

Note: This bridge will continue to deteriorate, holes have formed in the deck and the structure may become

unsafe to use in the next 20 years. The bridge may not be safe for vehicular traffic. If this bridge is to remain,

a load rating should be performed.

Prescription

This bridge will not support machinery. Works planned for site 7 require removal of this bridge for access.

• Bridge superstructure and cribbing should be removed.

• Pull back all materials adjacent the creek to create a broad swale, and armour stream crossing with

coarse rock

• Supervision of deactivation works by a qualified registered professional is recommended.



Photo 5.16.1 – Bridge at ∆202, (“Site 8” in Silvatech 1998 report)



5.17 Gold Creek – Site 9 / 10

Location: Block 502-3 Road

Map Reference: G-9, G-10

Field Identification: ∆113, ∆114

Previously identified issues (9) Failed 400mm CMP, water running along road surface, then back into natural channel.

(10) Infilled ditch is causing creek to flow down the road.


Observations A number of diversions of natural drainage paths along the road system were observed. This road system

should be deactivated and have natural drainage patterns restored.

These sites are not part of the Gold Creek watershed and drain to the watershed to the west. This road system

has not been deactivated, and though no significant issues were identified at the specific sites addressed in this

report, ( 9 and 10) the entire road system accessing Blocks 502 1-6 should be assessed in detail and

deactivated. These roads and blocks are located on the plateau, with drainage to the west into a deeply incised

creek draw. The draw is mapped as terrain class IV and V (potentially unstable and unstable).

Risk Analysis There is judged to be a moderate likelihood that improper drainage management in this entire road system

(including sites 9 and 10) could lead to drainage diversions which would result in landslides in the class IV and

V terrain in the watershed downslope (to the east). This could result in significant disturbances in the

watershed and subsequent downstream effects on Adams Lake. This is considered a high consequence. The

risk is therefore high.

Prescription

• At stations ∆113, ∆114 and ∆115 (corresponding to the area of Silvatech (2004) sites 9 and 10),

culverts should be removed and cross ditched.

• This entire road system associated with Blocks 502 (1-6) should have a deactivation prescription

prepared as it presents a possible gentle-over-steep hazard. (note: Preparation of deactivation

prescriptions for this area are planned for Summer of 2007)



Photo 5.17.1 – Blocked culvert causing ponding in ditchline with seasonal runoff over road.

Photo 5.17.2 – Damaged culvert at “Site 9” (∆114)



5.18 Rock Creek – Site 1

Location: Forest Service Rec. Site (“Silviculture Camp”) at Tsikwustum (Rock) Creek.

Map Reference: R-1


Previously identified issues Considerable bank erosion along right bank adjacent to rec site.

Potential to loose rec. site land, sediment delivery to creek and lake.

Restoration undertaken Unstable bank material was excavated back, and separated boulders placed as armour at the toe of the bank and

the area was grass seeded.

Observations The forest recreation site is located on the right bank of Tsikwustum (Rock) Creek, at the mouth of the river on

Adams Lake. This recreation site is built on an active fan, and as such is subject to large debris flood events,

and large annual high flow events.

There is a 1-4m high bank along the edge of the site (see composite photo 5.18.1) that had been sloped back

and armoured in 2004. The bank is being eroded and there is undercut portion of this bank adjacent to the

recreation site. Toe protection on the bank appears inadequate, as further erosion has taken place (compared to

2004 photos). Erosion is being accelerated by human activities; there is evidence in this area of disturbance by

campers (walking access, digging). A large open grassy area (grass seeded in 2004) is located adjacent to the

bank, as well as an access route to one of the lower camp sites.

Note: A large flood event could significantly impact the camp site. This assessment addresses only on the

possibility of sediment delivery to the creek as a function of normal (annual) high flows at the site indicated in

the Silvatech (2004) report. No evaluation of risk to the site infrastructure or human life is made with respect

to large, low return period flood events. Such an assessment is likely warranted, and should be carried out

separately.

Risk Analysis There is judged to be a moderate to high likelihood of further erosion along this slope, resulting in delivery of

sandy material to Rock Creek. This is likely to occur during flood / high water events, and would be

significantly diluted. This is therefore considered a low to moderate consequence. The risk is therefore

moderate to high

Prescription

• Slope back steep section (blue arrows in photo 5.18.1) where overhang and exposed roots threaten to

collapse.

• Place large rip rap (~2m diameter) at the base of the section ∆52 to ∆53, slope back top of the bank and

grass seed.

• Restrict vehicle access at the top of the bank by placing a row of large boulders ~ 5m back from the top

of the break in slope

• Consider restricting access with a fence along the top bank leaving a well marked path to the river to

limit bank disturbance.

• Continue to monitor site, inspect after high flow events.



Photo 5.18.1 – Photo composite – Eroding bank of Rock Creek adjacent to Silviculture Camp Forest Rec. Site.

Photo 5.18.2 – Detail of eroding bank.

∆∆∆∆52

∆∆∆∆53




Location: Tributary to Rock Creek

Map Reference: R-2


Previously identified issues 1800 mm CMP plugged with woody debris. Cutslope to the east (bush side of crossing) is delivering fine

sediment

Restoration undertaken Culvert has been cleared

Observations Culvert log jam has been cleared, and is now unobstructed. Given the size of this creek, there is a moderate to

high likelihood that future jams will take place. The recommendations in the Silvatech (2003) report to inspect

the culvert frequently (twice per year); this should be done prior to and following freshet. A large jam could

cause a significant blockage and subsequent debris flow at this site that would impact the S3 reach of Rock

Creek downstream.

The large cutslope to the east of the site continues to ravel and has infilled the ditchline, causing ditch flows to

flow across the road and onto the fillslopes on the bush side of the crossing (see photo 5.19.1 ; blue arrow

indicates flow). This is leading to erosion of the fillslope and deposition of sediment into the stream. If this

condition persists, it could lead to more significant erosion and / or fillslope failures.

Risk Analysis There is judged to be a moderate likelihood of a significant washout of the road, resulting in significant

sediment delivery and possibly a debris flow in the creek. This is considered a high consequence. The risk is

therefore high

Prescription

• Inspect culvert regularly (twice per year; prior to and following freshet)

• Clean and widen ditchline, carry flow to crossing (red arrow in Figure 5.19.1)

• Grass seed ditch and cutslope by hand or optionally hydroseed slope if feasible as per Silvatech (2003)

.



Photo 5.19.1 – Rock Creek tributary (Site 2 Silvatech 2003) ∆51 in field

Photo 5.19.2 – Rock Creek tributary culvert inlet




Location: Slide S-19 downslope of Rock Creek road near bridge crossing

Map Reference: R-3


Previously identified issues Surface soils in slide susceptible to surface erosion, sediment delivery potential to creek is high.

Restoration undertaken Has been hand grass seeded several times.

Observations The slide location is at a low point on the road, there is a long ditch run to this point, and water likely had

saturated the road prism / run over the edge at the slide site. Perched fill materials are still present and are

prone to ravelling. The slide is partially revegetating, some grass seeding has taken on the lower portions, but

the steep upper portion is likely to continue to be a sediment source. Rock Creek (S2) is located directly

downslope.

Risk Analysis The site is a permanent sediment source because slopes at the top are too steep to revegetate. There is judged

to be a moderate likelihood of a small slide initiating on oversteepened materials at the headscarp of the slide

with resulting minor sediment delivery (<5m3) to the S-2 creek downslope. This is considered a moderate

consequence. The risk is therefore moderate.

Prescription

• Carefully pull back top of slide area to 1.5V:1H (66%) maximum slope for the top portion of the slide.

• Hand-grass seed the slope.

• Upgrade ditchline along road this site.



Photo 5.20.1 - ∆50, slide S-19 looking down at exposed soils.




Location: Non-status road near reach break 5/6

Map Reference: R-4


Previously identified issues Erosion along 9m length of left bank of road poses a risk to the road and is a minor sediment source to the

creek.

Restoration undertaken Done as per Silvatech (2003) report

Observations This is a broad low gradient reach, with significant coarse woody debris in creek. Comparison of pictures of

previous site suggests low debris movement. Stream is classed as S2. Site has been restored, and remaining

ravelling is expected to be very minor. Site is revegetating, road surface erosion has ceased.

Risk Analysis There is judged to be a low to negligible likelihood of delivery of significant sediment to Rock Creek at this

site.

Prescription

• None / continue to monitor site.




Location: Non status road (Tsikwustum Lake Road) near junction with

Branch “C” Block C-206.

Map Reference: R-5


Previously identified issues Erosion of road surface near 450mm CMP due to plugged inlet – 50% function only.

Restoration undertaken None (Pre work indicated done)

Observations The ditch block at the 450mm culvert has failed, and flow has eroded ditchline. Drainage flows through

1000mm CMP downstream. There is significant flow coming down the ditchline that has eroded the

ditchblocks of the culverts upstream, and has resulted in significant sediment mobilisation (photo 5.22.1) in the

ditch and subsequent deposition (photo 5.22.2) in the ditch at lower gradient areas. Sediment is being

transported downstream, with significant aggradation in the channel and fines washing into Rock Creek.

Restoration at this site should be done in conjunction with remainder of the road to the east (Sites 6 and 7).

The culvert is experiencing severe piping because of excessive flows at this site, and material is eroding at the

outlet.

Risk Analysis There is judged to be a high likelihood that the culvert at this site will continue to fail and erode sediment

form the outlet and road surface. This will result in significant fine sediment transport downstream to Rock

Creek. This is considered a high consequence. The risk is therefore high

Prescription

• Repair (re-install) culvert (600mm CMP minimum) and armour sump.

• Ensure drainage measures in ditch upstream are addressed.

• Repair in conjunction with Site 11 (R-11) deactivation.



Photo 5.22.1 Erosion of ditchline

Photo 5.22.2 - Significant deposition at low point before culvert.




Location: Non status road (Tsikwustum Lake Road)

Map Reference: R-6


Previously identified issues Non functioning culvert is filly suspended above ditch, which has downcut ~0.4m in sandy materials.

Restoration undertaken None (Pre work indicated done, but comparison to Silvatech report photos reveals site has not been repaired)

Observations Culvert is still fully suspended and ditchblock has not been repaired. This is resulting in severe ditch runs

downstream, scouring ditchline and transporting sediment to Site 5, and subsequently to Rock Creek.

Risk Analysis There is judged to be a high likelihood that the non-functioing of this culvert will will result in significant

runoff and subsequent fine sediment transport downstream to Site 5 and then Rock Creek. This is considered a

high consequence. The risk is therefore high

Prescription

• Install large ditch block, constructed out of large rock.

• Install broad failsafe cross ditch to prevent further breaches of the ditch block.




Photo 5.23.1 – Eroded ditchblock at ∆42 (R6)

Photo 5.23.2 – Perched Culvert at ∆42 (R6)





Map Reference: R-7


Previously identified issues Piping of fine-textured soils at a 1400mm culvert has caused slumping of road surface.

Restoration undertaken Road repaired

Observations The culvert at this site is functional and in good condition. The ditch block and sump may have been

overtopped, at some point in the past resulting in increased flow down the ditch line.

Risk Analysis There is judged to be a low likelihood that the ditch block will be overtopped and eroded and result in further

significant runoff and subsequent fine sediment transport downstream to Sites 5 and 6 and subsequently to

Rock Creek downstream. This is considered a high consequence. The risk is therefore moderate.

Prescription

• Improve ditch block with large rip-rap


Photo 5.24.1 culvert inlet and ditchblock





Map Reference: R-8


Previously identified issues Inlet slumping, piping of fine textured materials.

Restoration undertaken Repaired road and armoured inlet.

Observations 1000mm CMP. Site has been repaired using coarse materials. No recent significant sediment production was

noted. Note that this stream is connected to the streams diverted at site 11. this site should be monitored after

restoration, to ensure flow capacities and sediment mobilisation changes are noted.

Risk Analysis There is judged to be a low likelihood of significant sediment production at this site. Further deterioration and

piping of fines would transport sediment to a fish bearing portion of the reach immediately downslope, with a

high to moderate likelihood of deposition of materials into Tsikwustum Lake. This is considered a high

consequence. The risk is therefore moderate.

Prescription

• Continue to monitor site

• Ensure site 11 restoration (R-11) does not divert excessive flows to this stream




Location: Branch “D”

Map Reference: R-9

Field Identification: ∆14 (∆9-∆16)

Previously identified issues Waterbars and cross-ditches between Tsikwustum Lake Road and the first junction off branch road “D” are

filling with sand and losing functionality.

Restoration undertaken Reported as done as per Silvatech (2003)

Observations Waterbars have been improved but problems of road surface erosion still present. Sandy soils highly prone to

erosion. Additionally, ditchlines experiencing significant erosion. Culvert ditch block at ∆9 could fail,

diverting significant drainage to lower ditch. Waterbar at ∆13 infilling. This road system is intercepting and

diverting significant flows. Full deactivation should likely be considered for the future.

Risk Analysis There is judged to be a moderate to high likelihood of road surface degradation and sediment production on

this road section, however there is no direct connectivity to Rock Creek. Road surface degradation is

considered a low consequence. The risk is therefore low.

Prescription

• ∆9 – Improve failsafe cross ditch. Riprap ditchblock.

• ∆10 – Improve waterbar

• ∆12 – Install failsafe cross ditch

• ∆13 – Clean / improve backup cross ditch



Figure 5 – (Site R-9), Branch D Road

Photo 5.25.1 – ∆9 existing 600mm CMP

Branch D

Rock Creek Main




Location: Branch “D” crossing on Tributary #1

Map Reference: R-10


Previously identified issues A section of approximately 500m of road is at risk of erosion by tributary #1 had breached a ditch block at a

1400mm CMP resulting in streamflows being routed along the ditch, and had washed out a block of a 600mm

ditch block downslope.

Restoration undertaken Work done by Interfor as per instructions provided by Silvatech in September 2002

Observations Large ditchblocks put in place at 1400mm culvert and at 600mm downslope. Ditchblocks functioning.

1400mm ditch block is adequate, but contains a high proportion of fines and rock of smaller diameter and may

be washed out in the event of an extreme flow. Ditchblock construction at 600mm culvert is very good. There

are no failsafe cross ditches in place.

Risk Analysis There is judged to be a moderate likelihood of the ditchblock at the 1400mm pipe to be breached, resulting in

another stream avulsion and subsequent ditch erosion and sediment production. The area downstream of the

two culverts is flat and marshy, and any sediment entrained is likely to settle out before entering Rock Creek.

This is considered a low consequence. The risk is therefore low.

Prescription

• Improve ditch block at 1400mm culvert with large diameter rock

• Install broad failsafe cross ditches at both culvert locations



Photo 5.27.1 – 1400mm culvert with ditchblock

Photo 5.27.2 – Ditch block at 600mm Culvert




Location: Branch “C”

Map Reference: R-11

Field Identification: ∆19-∆40, ∆131-133

Previously identified issues Severe ditch erosion along 75m of road has resulted in a deep ditch in sandy tills. Sediment delivery to stream

network moderate.

Site R11 was examined as part of the current study. It was determined from this initial investigation that

additional issues with drainage diversions in the road network upslope of the site were contributing to the

problems identified at site R11. It was decided that a second, more detailed investigation should be carried

out. This separate investigation was done on October 20 2006 by the author, and has been included in this

final revision of the report.

Restoration undertaken None evident.

Observations

The original study and the follow-up detailed study focused on the two road systems, Branch “C” and the

associated spur to the south (See Figure 6).

Soils in this area consist of a veneer to blanket of sandy tills and bouldery glacio-fluvial materials over

relatively impermeable gneissic bedrock. There is significant shallow groundwater flow which has been

intercepted by road construction and exacerbated by harvesting in this area. As a result, ditch flows are

significant, and diversions have led to washouts in culverts downslope, notably at assessment Sites 5, 6 and 7.

At site R11, the ditch and road surface have been severely eroded and a significant amount of sediment has

been mobilised in the ditchline and where the ditch flow has washed out the road. The ditchline had eroded to

a significant depth, and original crossdrains / culverts have been perched

The upper portion of Branch C has been deactivated from ∆1 to ∆18. This portion of the road is not

contributing to the drainage issues identified in the previous studies, and only minor remediation, if any, is

required

It appears that interception of subsurface groundwater and subsequent diversion by roads and trails in the area

of the branch to the south of (Waypoints 104-138) have contributed to the excessive ditch flows on Branch C.

The spur road has been deactivated, with frequent cross ditches dispersing drainage, and natural stream

channels have been restored to satisfaction at waypoints ∆100 and ∆131. The road surface in this area is

revegetating, and sediment production is minimal in this area. The lower portion of the spur, from ∆131 to

the POC with Branch C has also been deactivated, however the deactivation has been in large part

unsuccessful, and significant water is intercepted and channelled along the road surface and ditch to Branch C.

Waterbars in this area need to be extended as cross ditches from stations ∆131-∆133.

Risk Analysis Due to drainage interception/diversion and concentration, there is judged to be a high likelihood of further



sediment production at these sites, with a moderate likelihood of sediment delivery to the stream system (S5

stream through R7 and the S6 stream through R6) and subsequently to Rock Creek (S2). This is considered a

high consequence. The risk is therefore high

Prescription

The following prescription is meant to disperse ground water flows as much as possible where such flows have

been intercepted and concentrated as ditch flows, as well as to restore stream flows to natural channels where

these may have been diverted by road construction.

Note: all cross ditches on this road section should be deep enough to intercept all ditch drainage, and should

be broad, with gentle approaches. Armour all cross ditches with large rock. Install ditch blocks constructed

with coarse rock and boulders.

Branch C Road

• ∆1 existing cross drain - no action required

• ∆2 existing 500 CMP at low point in road with functioning failsafe cross ditch - no action

required

• ∆3 500 CMP, perched inlet. Low risk - no action required

• ∆4 500 CMP, good ditchblock in place Low risk - no action required

Stations ∆6, ∆7, ∆9, ∆10, ∆11, ∆13, ∆14, ∆16, ∆17 are all existing cross ditches, functioning well, low risk. -

no further action required

• 17B POC of several spurs upslope, start of deepened ditchline - no action required

• ∆18 500CMP, ponding upslope - Pull culvert and install broad armoured cross ditch. and ditch

block

• ∆20 Existing waterbar – install broad armoured cross ditch and ditch block

• ∆20A Install broad armoured cross ditch and ditch block. Extend cross ditch south to ribbon, to

intercept surface flows on old trail on south side of ditch.

• ∆21 S5 Stream, ditch block has been overtopped leading to significant diversion. - Install broad

armoured cross ditch and ditch block.

• ∆21A Existing culvert, significant seepage from old spur upslope. - Pull culvert and install broad

armoured cross ditch. and ditch block

• ∆22 Existing culvert - Pull culvert and install broad armoured cross ditch

• ∆23 Existing culvert - Pull culvert and install broad armoured cross ditch, install ditch block on

bush side



• ∆25 Install broad armoured cross ditch and ditch block

• ∆26 500 CMP with good ditch block - Pull culvert and install broad armoured cross ditch. and

ditch block



• ∆29 S6 channel - Install broad armoured cross ditch and ditch block, restore natural stream

channel.

• ∆30 - ∆31 Construct a large armoured cross ditch from station ∆30 to ∆31 across the POC of the spur

road to the south, and across Branch C. The intent of this ditch is to channel runoff from the spur to the

S6 which crosses at ∆29. Ditch should have a gradient of 2-3%. Install a large ditch block in the

existing ditch.

• ∆32 Exisiting cross ditch is perched. - Install broad armoured cross ditch and ditch block


• ∆34 Exisitng 500 CMP – Pull culvert Install broad armoured cross ditch and ditch block



• ∆39 Low gradient portion of road. - Install broad armoured cross ditch and ditch block – angle

ditch across as indicated by ribbons.

Spur Road

• ∆131, ∆132, ∆133 Existing waterbars do not intercept the ditchline, leading to significant ditch

flows. – cross ditch waterbars to ditch line (drain ditch flow across road to disperse drainage)



Photo 5.28.1 – severe ditch erosion.



Figure 6 – (Site R-11), “Branch C” Road detail




Location: Non-Status Road (Tsikwustum Lake Road) – north end of Tsikwustum Lake

Map Reference: R-12


Previously identified issues 400mm culvert draining a small pond plugged with woody debris. Evidence of flooding on road surface.

Restoration undertaken None evident

Observations Culvert inlet obscured by woody debris, but pond has drained. Inlet of culvert completely blocked by coarse

woody debris. Road shows signs of being overtopped by seasonal flows resulting in road surface erosion.

Culvert is located in large road fill, removal would likely result in road being impassable. Creek is classed as

S3, but fish passage is not possible upstream of this location. A fish passage assessment should be performed

at this site.

Risk Analysis There is judged to be a moderate likelihood of a road washout in this location, resulting in delivery of

sediment to the S3 class stream and subsequently to Tsikwustum Lake, and loss of use of the road. This is

considered a moderate consequence. The risk is therefore moderate.

Prescription

Depending on management objectives:

• Pull culvert and pull back fill material and armour crossing with rock

OR

• Install failsafe cross ditch and continue to monitor site and clean out as necessary.

• A fish passage assessment should be performed at this site.



Photo 5.29.1 – ∆45 “Site 12” Ponding upstream of culvert.




Location: Permitted Road (Tsikwustum Lake Road) – Near Branch “E” Junction

Map Reference: R-13


Previously identified issues Surface erosion at a 600mm CMP possibly due to undersized culvert.

Restoration undertaken Replaced with 1000mm CMP

Observations 1000mm CMP on S4 class creek, functioning normally. Minor sediment production on cutslopes.

Risk Analysis There is judged to be a low to negligible likelihood of further sediment production at this site.

Prescription

• No further work required

Photo 5.30.1 – 1000mm CMP ∆48, “Site 12”




Location: Tsikwustum Lake Road (North Rock Creek Road)

Map Reference: R-14

Previously identified issues Road fill erosion and slumping at 400mm CMP. Sediment source with a high potential to enter stream

network.

Restoration undertaken Culvert replaced, works completed as per Silvatech (2003) report.

Observations Culvert replaced with 800 mm CMP – functioning. No apparent issues since replacement. Connectivity to S2

immediately downstream.

Risk Analysis There is judged to be a low to negligible likelihood of further sediment production at this site.

Prescription




5.32 Mosquito Creek (Site 1)

Location: Mosquito Creek

Map Reference: M-1


Previously identified issues Stream diversions

Restoration undertaken Works as prescribed by Silvatech (2004) report completed by October 29, 2004.

Observations Works completed as described in Silvatech (2004) report were reviewed. This report recommended grass

seeding, which appears to have been completed to satisfaction. Cross drain structures and culverts have been

put in place. Flow appears to have been redirected back to the original stream locations satisfactorily. There is

some evidence of minor road surface runoff taking place – the road has been rutted by vehicle traffic, and

minor runoff is eroding the road surface. This road surface flow is intercepted by waterbars and cross ditches,

and is only a minor concern. The road is still accessible by truck; consider limiting vehicle access to ATVs

only.

Concerns on the upper rehabbed portion of road are generally with shallow cross drain structures which could

fail and divert drainage down the road, and lack of failsafe cross ditches at culvert locations, where a blockage

would send water down ditchlines, altering natural drainage patterns.

∆55-∆56 – a portion of the cross drained flow runs down the ditch and partly down the road surface. Although

it is intercepted by the cross ditch at station 56. At ∆58 – creek crossing – cross ditch is not sufficiently deep,

large flows could run down the road. The ditchline from ∆62 back is taking substantial flows. Base mapping

provided indicates that this flow comes from a stream which has been diverted along the ditch line, and had

been ditched across the new road at the switchback (∆66). There is an armoured cross ditch at ∆63, which puts

this stream back into what appears to be a the natural channel again. This stream then joins the S5 stream,

crossing the road at ∆67 in a 1200mm culvert. The 600mm culvert at ∆66 (previous diverted flow path) is now

experiencing only minimal flows. There is a failing box culvert at ∆69, which is only about 30% effective and

will soon fail.

Risk Analysis There is judged to be a moderate likelihood of ditch flows and cross drained flows running over or down the

road surface due to shallow / non-existent waterbars / failsafe cross ditching. This would result in road surface

erosion and drainage diversions on the access road and sediment delivery to S-6 and S5 classed streams. This

is considered a moderate consequence. The risk is therefore moderate.

Prescription

• ∆55-56 Install waterbars to remove road surface diversions

• ∆58 Deepen cross ditch.

• ∆61 Install failsafe cross ditch

• ∆67 Install broad shallow failsafe cross ditch – large flow potential, and overflow could run down



road.

• ∆66-71 Significant sediment production in ditchline, seepage all along this ditch. Grass seed.

• ∆69 Replace failing box culvert with 800mm CMP.

• ∆70 600 CMP Install broad backup cross ditch.

• ∆71 500 CPP Install broad backup cross ditch.

Consider restricting the deactivated portion of the road to ATV traffic only to minimise sediment

production from rutting.

Note: The road back of ∆71 to the road junction is cut into poorly consolidated weathered schistose bedrock

and tills. Ditchlines are slumping and infilling. This road will require inspection and significant maintenance

measures (beyond the scope of this assessment)

Photo 5.32.1 – ∆59 Road surface drainage being intercepted by Cross Ditch, grass seeding effective.



Photo 5.32.2 – ∆69, Failing wood culvert



Figure 7 – Mosquito Creek Site 1 Detail



5.33 Honeymoon Bay (Site 2)

Location: Honeymoon Bay recreation site.

Map Reference: H-2

Previously identified issues Grass seeding may be required in areas of previous restoration works.

Restoration undertaken • Ditch line cleanout

• Half-waterbars allowing trailer access to rec. site.

• Construction of rock weirs in ditching and settlement ponds at the lower end adjacent to the lake

• Minor grading of road surface

• CMP cleanout, armour ditch in areas of past erosion / concentrated flows

Observations

Works as described in Silvatech (2004) report have been completed. Ditchline clean and functioning, some

grass and shrub vegetation establishing naturally. Road cut materials exposed and some ravelling into ditchline

taking place.

Shallow waterbars are located on the upper portion of the road, and are effectively draining road surface runoff

into the ditchline. These are starting to wear / infill due to traffic with some washboarding taking place.

The sumps for the two 300 mm pipes appear to have been very recently cleaned out (Spring 2006?) The

material removed has been piled directly adjacent to the sumps and is slumping back in. Drainage laden with

fine sediment is discharging into the lake directly below (See photos 5.33.1a-5.33.1c). Culverts are undersized

and have a high likelihood of becoming plugged.

Risk Analysis There is judged to be a high likelihood of continuous delivery of a small amount of fine sediment via the

ditchline and inadequate sumps at the culvert inlets to Adams Lake. This is considered a low consequence.

The risk is therefore moderate.

Prescription

• Remove slumping material adjacent to culvert sumps, establish broad shallow armoured sumps and

grass seed.

• Grass seed ditchline and cut slopes as prescribed in Silvatech (2004).

• Monitor and maintain waterbars on upper portion of access road.



Photo 5.33.1a– Honeymoon Bay – 300mm pipe at end of ditch above lake.

Photo 5.33.1b – Honeymoon Bay. Sump at end of road, appears recently cleaned out.



Photo 5.33.1c – Honeymoon Bay. Culvert discharge directly into lake.

Photo 5..33.2 – ∆76 – Berm deflecting creek drainage down ditchline.



Photo 5.33.3– Improved ditchline on Honeymoon Bay recreation site road.



5.34 Momich Lake Site 3

Location: South of Momich Lake

Map Reference: M-3

Previously identified issues Old log box culvert – holes have developed in the road, with water passing beneath the road. Road has

existing deactivation.(Silvatech 2004)

Restoration undertaken This site is located near the end of a road which has been deactivated (primarily cross ditched) and is

revegetating.

Observations

The road has been deactivated with frequent cross ditches and is revegetating with alder and immature

coniferous species. The site in question is an old log box culvert which is conveying water under the road

surface. Holes have formed in several places. Immediately downslope of this site, the outlet of this cross

drainage is armoured with very large boulders (>1.5m diameter). The site is in a broad shallow draw. Slopes

below are planar at about 40-45%. There is a failsafe cross ditch in place. The road prism is unlikely to fail

catastrophically, and blockage of the current flow would be conveyed across the road surface in the failsafe

back into the natural channel.

Risk Analysis Because of the existence of a backup cross ditch and heavy armouring of the outlet, There is judged to be a low

to negligible likelihood that this failing log box will significantly in a slope failure.

Prescription

Removal of this structure will not result in a significant reduction in risk, and bringing equipment up this

already deactivated road is likely to result in excessive disturbance.




Photo 5.34.1 – Site 3 Momich Lake area.



5.35 Momich Lake Site 5

Location: South of Gannet Lake

Map Reference: M-5


Previously identified issues Ravelling has blocked a culvert.


Observations Culvert inlet almost entirely blocked by boulders but still partially functioning. Cross drain culvert taking

about 5% of the flow. Significant stream upslope could lead to large washout if not repaired.

Risk Analysis There is judged to be a high likelihood of the culvert completely failing and causing a washout resulting in

sediment delivery to the S5 stream downslope, with a moderate likelihood of sediment delivery to the S3 reach

of the same stream. This is considered a moderate consequence. The risk is therefore high.

Prescription

• Clean out or replace culvert

OR

• Pull culvert and re-establish natural stream course.

Photo 5.35.1 – Site 5 Gannet Lake area.



6.0 Closure

This assessment focussed primarily on previously identified sites, but observations of general watershed

condition and sediment sources and other potential problem areas were noted.

Several natural sediment producing sites were noted during the Gold Creek helicopter overflight, but no

additional areas with significant issues related to forest harvesting or road construction, other than those

identified in this report, were observed.

This risk analysis has been carried out in accordance with generally accepted engineering and geoscientific

practice for the area. Conclusions and recommendations presented herein are based on air photo interpretation

and visual site inspections of selected areas in each watershed. Further, assessments of soils and slope stability

are based on interpretation of surface features and limited sub-surface investigation; actual ground conditions

may vary from those inferred.

This report provides a qualitative evaluation of hazards associated with sites previously identified in the study

area, a description of the potential consequences, and recommendations to reduce the hazards and associated

risks. Acceptance of the qualitative consequence values and the subsequent risk analysis is the responsibility

of the licensee or the regulatory authority, as is the determination of acceptable risk and the decision to proceed

with any action based on that risk analysis.

We trust that this report satisfies your present requirements. Should you have any questions or comments,

please contact our office at your convenience.

Sincerely,

Forsite Consultants Ltd.

Prepared by: Reviewed By:

Peter Weisinger, M.Sc. G.I.T. Rod Williams, P.Geo

Project Geoscientist Project Geoscientist