Tender No.: 7559/07
PART 1
GENERAL
1.1
GENERAL
.1
1.2
Section 02242
Turbidity Barriers
Page 1
The Contractors operations will be subject to the maximum allowable increase in
total suspended solids (Max-TSS) within the watercourse.
DEFINITIONS
.1
“Instream” means those parts of the bed and banks of a water body that are both
with and without terrestrial vegetation.
.2
“Max-TSS” means the maximum allowable increase of total suspended solids in
the watercourse from the levels at the compliance point downstream of the
turbidity control structure from those immediately upstream of the worksite
containment.
.3
“Visually Conspicuous Plume” means a plume of suspended solids that can be
visually observed in the watercourse.
.4
“Normal Construction Activity” means any construction activity that will not cause
elevated turbidity levels, and no visual indications of elevated turbidity levels.
.5
“Scheduled Construction Activity” means any planned activity that can be
expected to result in additional turbidity in the watercourse, including the
installation and removal of cofferdams, silt curtains, placing of riprap in the water,
grading, etc.
.6
“Accidental Occurrence” means any situation, beyond the Contractor’s control,
that results in elevated turbidity levels in excess of the specified compliance
limits, including situations like the unexpected breaching of a cofferdam due to
flood conditions exceeding the design levels.
1.3
SAMPLING AND TESTING (QUALITY CONTROL AND QUALITY ASSURANCE)
.1
Perform all sampling and testing of total suspended solids as specified herein.
.2
Provide copies of the results of all sampling and testing in a daily summary
format. Upon completion of Construction Activities, submit a final report
containing all sampling and testing data.
.3
The Minister will carry out random quality assurance inspection as a means to
monitor the Contractor’s quality control program. Assist and cooperate with the
Minister during the collection of water quality samples.
.4
Prior to the start of construction, carry out sufficient testing to determine the
normally occurring linear relationship between total suspended solids
Section 02242
Turbidity Barriers
Page 2
Tender No.: 7559/07
concentration and turbidity in the watercourse. Pay services of a qualified
laboratory to determine the relationship.
.5
Take at least 15 test samples and establish the linear relationship. Follow the
procedures
outlined
in
www.transportation.alberta.ca,
Environmental
Management.
.6
During construction, perform the following:
1.4
.1
Measure the suspended solids in Nephelometric Turbidity Units (NTU)
accurate to within 2%.
.2
Convert NTU into mg/l using the industry standard method.
.3
Measure upstream and downstream NTU levels within 30 minutes of each
other, unless there is a sediment release (see monitoring frequency
below).
.4
Take one measurement at one-half the depth of the watercourse for
watercourses less than one metre in depth. For watercourses greater than
one metre in depth, take two measurements, one at 20% depth and one at
80% depth of the watercourse.
SAMPLING FREQUENCY
.1
Perform total suspended solid sampling at the following frequency:
Site Condition
Monitoring Frequency
Normal Construction Activities
During instream work, sample twice a day,
at intervals more than eight hours apart,
both at the upstream background site and
all specified downstream compliance sites(1).
Scheduled Construction
Activities and Accidental
Occurrences
During daylight hours, sample as frequently
as possible, and as directed by the Minister,
at the upstream background site and the
specified downstream compliance sites until
total suspended solids (TSS) levels have
returned to acceptable background limits.
Note(1):
With prior approval of the Minister, testing frequency may be
reduced if the Contractor’s environmental controls are determined
to be effective at controlling turbidity to less than 5 mg/l in excess of
normal background levels for a period of five consecutive days.
Section 02242
Turbidity Barriers
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Tender No.: 7559/07
1.5
COMPLIANCE POINT LOCATIONS
.1
Monitor the total suspended solids at the following compliance point locations:
Type of
Watercourse
Downstream
Compliance Point
Distance 1 (1)
Downstream
Compliance Point
Distance 2
Downstream
Compliance Point
Distance 3
Ponded systems such
as lakes, pools,
wetlands and similar
other waterbodies
where velocities are
less than 0.5 m/s
The lesser of 30 m, or
the maximum surface
dimension of the
waterbody. Samples
must be taken 30 m
apart around the
circumference of the
turbidity barrier.
20 m (dependent on
the size of the
waterbody). Samples
must be taken 30 m
apart around the
circumference of the
turbidity barrier.
20 m (dependent on
the size of the
waterbody). Samples
must be taken 30 m
apart around the
circumference of the
turbidity barrier.
Wetted streams less
than 10 m wide
1 stream width
downstream (1)
2 stream widths
downstream (1)
3 stream widths
downstream (1)
Wetted streams
between 10 m and
30 m wide
30 m downstream (1)
60 m downstream (1)
90 m downstream (1)
Wetted streams
greater than 30 m but
less than 60 m wide
60 m downstream (1)
120 m downstream (1)
180 m downstream (1)
Wetted streams
greater than 60 m
wide
90 m downstream (1)
180 m downstream (1)
270 m downstream (1)
Note (1):
If there is a plume then measure total suspended solids at various locations
across the watercourse, in accordance with the following:
1. Take samples from the middle of the plume.
2. Take samples as close to the source of the plume as possible (within safety
limits).
3. If the watercourse is less than 5 m wide then only one measurement is
required across the stream width. Take measurement within the plume.
4. If the watercourse is greater than 5 m wide, measurement must be taken at a
minimum of three locations across the watercourse; within the plume, halfway across the channel, and 2/3 of the channel width measured from the
bank closest to the point where the discharge originated.
Section 02242
Turbidity Barriers
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Tender No.: 7559/07
1.6
MAXIMUM ALLOWABLE INCREASE OF TOTAL SUSPENDED SOLIDS
.1
Visual Limits
.1
.2
In the event that a Visually Conspicuous Plume does exist, cease all
activities which will have the potential to generate sediment in the
watercourse.
Compliance Criteria
.1
Criteria are set by the Canadian Council of Ministers of the Environment
Guidelines.
.2
Utilize equipment, labour and procedures in a manner that ensures the
maximum allowable levels of suspended solids are maintained at or below
the following levels:
Site Conditions
Compliance Criteria – (MAX-TSS
in Excess of Normal Background
Levels)
Contractor Action if TSS
exceeds the Compliance
Criteria
Normal Construction
Activity
5 mg/l in excess of normal background
levels is continuously allowed (2)
Notify the Minister immediately.
Cease all instream work and
immediately initiate remedial works.
If compliance criteria is exceeded
for 2 or more hours, follow the
Contractor Actions for Accidental
Occurrences and/or Scheduled
Construction activities.
Accidental
Occurrences
150 mg/l not exceeding 2 hours in
duration and at no time exceeding 250
mg/l (3)
Notify the Minister immediately.
Cease all in-stream work and
immediately initiate remedial works.
If compliance criteria is exceeded
for 2 or more hours, notify
authorities for Regulatory
Requirements in accordance with
the Environmental Management
System Manual.
Section 02242
Turbidity Barriers
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Tender No.: 7559/07
Scheduled
Construction Activities
When background levels are less than
or below 250 mg/l (2)
1. A maximum increase of 25 mg/l
2. 5 mg/l for a 30 day period
3. 25 mg/l for a 24 hour period
4. At no time are 250 mg/l to be
exceeded
When background levels are above
250 mg/l
1. TSS may be increased by 10%
above background levels for a
24 hour period
2. TSS may be increased by 2%
above background levels for a
30 day period
Note (2):
Note (3):
1.7
Notify the Minister immediately.
Cease all in-stream work and
immediately initiate remedial works.
Complete the Scheduled
Construction activities in an 8 hour
day or cease all instream works until
TSS levels return to acceptable
limits.
If compliance criteria is exceeded
for 2 or more hours, notify
authorities for Regulatory
Requirements in accordance with
the Environmental Management
System Manual.
The Canadian Council of Ministers of the Environment
Suggested guideline for Accidental Occurrences
.3
Notify the Minister at least 48 hours prior to the start of any Scheduled
Construction Activity.
.4
In the event of an Accidental Occurrence that results in a Visually Conspicuous
Plume of sediment, immediately notify the Minister and undertake any mitigative
actions necessary to comply with the specified compliance criteria.
SUBMITTALS
.1
Provide the following submittals:
.2
Shop Drawings of the turbidity barriers detailing the components and the material
specifications of the components, 15 days prior to commencement of the Work.
Provide a turbidity barriers system that has been designed and stamped by a
professional Engineer registered with the Association of Professional Engineers,
Geologists and Geophysicists of Alberta or a specialist in such Work authorized
by the Minister.
.3
Turbidity Control Execution Plan outlining the location of the turbidity barriers, the
method of installation, anchorage details, maintenance and inspection
procedures, the removal and storage procedures and contingency plans in case
of a breach in the turbidity curtain, 15 days prior to commencement of the Work.
.4
Final report referred to in 1.3.2.
Section 02242
Turbidity Barriers
Page 6
Tender No.: 7559/07
PART 2
PRODUCTS – NOT USED
PART 3
EXECUTION
3.1
INSTALLATION
.1
Install provisions for turbidity control at the Travers Inlet site during all
periods of construction that may impact the quality of water in Travers
Reservoir including at least the following:
.1
.2
Initial construction of the cofferdam.
Placement of riprap and bedding material.
.2
Install the temporary turbidity barrier system in accordance with the
turbidity control execution plan.
.3
Remove the turbidity barriers during the periods they are not required.
END OF SECTION