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Water Quality

WATER MANAGEMENT BRANCH
ENVIRONMENT AND RESOURCE DIVISION
MINISTRY OF ENVIRONMENT, LANDS AND PARKS

AMBIENT WATER QUALITY
ASSESSMENT AND OBJECTIVES FOR
THE COWICHAN AND KOKSILAH RIVERS
VANCOUVER ISLAND
OVERVIEW REPORT
Prepared pursuant to Section 2(e) of the
Environment Management Act, 1981
Original signed by Richard Dalon
Assistant Deputy Minister
Environment and Lands HQ Division
February 27, 1989.

Canadian Cataloguing in Publication Data

McKean, Colin J. P. (Colin John Pearce), 1955-
Cowichan-Koksilah Rivers water quality assessment and objectives

[Vol. 2] constitutes technical appendix.
Includes bibliographic references.
ISBN 0-7726-1606-x

1.  Water quality - British Columbia - Cowichan River.
2.  Water quality - British Columbia - Koksilah River).
I.  BC Environment.  Water Management Division. II.  Title.


TD227.B7M334 1992    363.73'942'097112    C92-092267-8

TABLE OF CONTENTS


SUMMARY

This report assesses the water quality of the Cowichan and Koksilah rivers located on the south-eastern side of Vancouver Island, and sets water quality objectives to protect their uses for drinking, irrigation, industrial consumption, water contact recreation and aquatic life.

The Cowichan River, which originates at the south end of Cowichan Lake, is the most important river on Vancouver Island for recreational fisheries (steelhead, cutthroat, rainbow, brown trout and kokanee) and commercail fisheries (coho, chinook and chum). The river is also important for water contact recreation such as kayaking, canoing, etc. and as a source of water for domestic, irrigation and industrial uses (BC Forest Products Crofton Pulp Mill). The Village of Lake Cowichan obtains its water supply from Cowichan Lake while the City of Duncan obtains its water from wells adjacent to the Cowichan River downstream from the Island Highway.

The Koksilah River is also important for recreational and commercial fish species as well as recreational activities and domestic, irrigation and industrial water supplies. However, since the river does not have a large lake within its watershed to provide water storage, summer stream flows are approximately 95% lower than flows in the Cowichan River. Consequently, the value of the above uses in the Koksilah River are reduced relative to the Cowichan River.

There are three permitted discharges on the Cowichan River. The sewage discharge from the Village of Lake Cowichan and the discharge of ground water used in a Ministry of Environment fish hatchery have little of no impact on the water quality of the Cowichan River. The third permitted discharge is sewage from the Duncan/North Cowichan treatment plant. The effluent is not adequately diluted in the Cowichan River during the summer low flow period. High concentrations of nitrogen and phosphorus cause excessive periphyton growth for several kilometers downstream from the discharge.

Water quality objectives are set in the Cowichan River for a number of possible contaminants. These originate from a sawmill located at Youbou, a small abandoned base metal mine adjacent ot Cowichan Lake, future base metal mining in the upper Cowichan watershed, public wharves near the outlet of the lake and the sewage discharges to the river.

Water quality objectives are set in the Koksilah River to protect water uses from two sources of contantamination: potential bacterial contamination from dairy farms near Dougan Lake and contaminants from the Cowivchan Valley Regional Distruict incinerator/landfill and gravel washing operations near Duncan.

Water quality objectives are set to protect the most sensitive water uses in both rivers. The objectives and a monitoring program for the Cowichan and Koksilah rivers are summarized in Table 1, Table 2, Table 3 and Table 4.

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Figure 1. Cowichan/Koksilah Basin Location Map
cowichan/koksilah basin location map
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PREFACE

Purpose of Water Quality Objectives

Water quality objectives are prepared for specific bodies of fresh, estuarine and coastal marine surface waters of British Columbia as part of the Ministry of Environment, Lands and Parks' mandate to manage water quality. Objectives are prepared only for those waterbodies and water quality characteristics that may be affected by human activity now or in the near future.

How Objectives Are Determined

Water quality objectives are based the BC approved and working criteria as well as national water quality guidelines. Water quality criteria and guidelines are safe limits of the physical, chemical, or biological characteristics of water, biota (plant and animal life) or sediment which protect water use. Objectives are established in British Columbia for waterbodies on a site-specific basis. They are derived from the criteria by considering local water quality, water uses, water movement, waste discharges, and socio-economic factors.

Water quality objectives are set to protect the most sensitive designated water use at a specific location. A designated water use is one that is protected in a given location and is one of the following:

Each objective for a location may be based on the protection of a different water use, depending on the uses that are most sensitive to the physical, chemical or biological characteristics affecting that waterbody.

How Objectives Are Used

Water quality objectives routinely provide policy direction for resource managers for the protection of water uses in specific waterbodies. Objectives guide the evaluation of water quality, the issuing of permits, licences and orders, and the management of fisheries and the province's land base. They also provide a reference against which the state of water quality in a particular waterbody can be checked, and help to determine whether basin-wide water quality studies should be initiated.

Water quality objectives are also a standard for assessing the Ministry's performance in protecting water uses. While water quality objectives have no legal standing and are not directly enforced, these objectives become legally enforceable when included as a requirement of a permit, licence, order, or regulation, such as the Forest Practices Code Act, Water Act regulations or Waste Management Act regulations.

Objectives and Monitoring

Water quality objectives are established to protect all uses which may take place in a waterbody. Monitoring (sometimes called sampling) is undertaken to determine if all the designated water uses are being protected. The monitoring usually takes place at a critical time when a water quality specialist has determined that the water quality objectives may not be met. It is assumed that if all designated water uses are protected at the critical time, then they also will be protected at other times when the threat is less.

The monitoring usually takes place during a five week period, which allows the specialists to measure the worst, as well as the average condition in the water.

For some waterbodies, the monitoring period and frequency may vary, depending upon the nature of the problem, severity of threats to designated water uses, and the way the objectives are expressed (i.e., mean value, maximum value).

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INTRODUCTION

This study assess the water quality of the Cowichan and Koksilah rivers which are located on south-eastern Vancouver Island (Figure 1). Three permitted discharges to the Cowichan River, a small abandoned base metal mine, public wharves near the outlet of the lake and an operational sawmill upstream from the Cowichan River, are potential sources of contaminants to the Cowichan River. Nonpoint nutrient and bacteriological loading from farms, and runoff from gravel washing operations near Duncan, are the potential sources of pollution in the Koksilah watershed.

This report discusses the water quality of the two rivers, interprets the impact of the non[point and point discharges and develops water quality objectives to protect the major uses of the rivers.

A detailed Technical Appendix was prepared by the author and forms the basis for the conclusions presented.

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HYDROLOGY

The Cowichan River begins at the outlet of Cowichan Lake. Like most coastal stream with little snow pack, maximum stream flows occur in the winter while low flows occur in the late summer and early fall. The summer flow of the Cowichan River is controlled by a weir at the outlet of Cowichan Lake. The weir is controlled by BC Forest Products in conjunction with a water storage licence for 62000 dam3 on Cowichan Lake. A rule curve specifies a minimum release of 7.08 m3/s from June 1 to October 15. The 7-day average low flow with a return period of 2 years (1-in-2-year, 7-day average low flow) of the Cowichan River at the outlet of Cowichan Lake is 6.87 m3/s which is slightly lower than specified by the rule curve. The BC Forest Products pulp mill at Crofton withdraws water from the Cowichan River near Duncan causing the lower Cowichan River to have a 1-in-2-year, 7-day average low flow of 5.25 m3/s.

The Koksilah River has very low stream flows during the summer (0.3 m3/s) principally because the river does not have a large headwater lake with water storage to augment summer low flows.

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WATER USES

In 1986 the mainstem of the Cowichan River had the following licences: 15 domestic, 3 waterworks (14230 m3/d), 3 irrigation (4.6 dam3/yr) and 1 industrial (BCFP, 244500 m3/d). The Koksilah River has 11 domestic licences, 16 irrigation licences (565 dam3/yr) and 4 industrial licences (5250 m3/d). Two of the industrial licences are used for gravel washing while the remaining two are for lean watering and fish culture.

The Village of Lake Cowichan anfd the City of Duncan do not obtain their domestic water from the Cowichan River. The Village of Lake Cowichan has water intakes at the east end of Cowichan Lake while the City of Duncan has wells located adjacent to the Cowichan River approximately 1 km downstream from the highway bridge.

The fisheries rersource of the Cowichan/Koksilah system has been estimated at 2 million dollars per year for sports fish (coho, chinook, steelhead, resident and anadromous trout), 2.5 million dollars per year in commercial fish (coho, chinook, chum) and 650 thousand dollars per year in angler-day value (cost of sport fishing). The Cowichan River contributes the bulk of the sport and commercial value ( approximately 80 to 90 percent).

Water based recreation is well represented along the Cowichan and Koksilah rivers. There are five provincial parks and other regional, municipal and community parks adjacent to the rivers. Kyaking and hiking trails are also important recreational uses of the watershed. Although no estimates of the recreational value are available, the Cowichan and Koksilah are considered to be recreationally important rivers.

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WASTE DISCHARGES

There are three permitted direct discharges into the Cowichan River. The Village of Lake Cowichan is permitted (PE 247) to discharge 1728 m3/day of treated (secondary) sewage that has been chlorinated and dechlorinated. The discharge is located about 3.5 km downstream from the outlet of Cowichan Lake.

The City of Duncan and the Municipality of North Saanich jointly operate a similar sewage treatment facility near the City of Duncan. The permit (PE 1497) allows the direct discharge of 13600 m3/d of effluent 1.5 km downstream from the highway bridge near the mouth of the river. The maximum discharge to date has been 7859 m3/day which is 57 percent of the maximum permitted discharge.

The third permitted discharge into the Cowichan River is ground water used for fish culture by a Ministry of Environment fish hatchery. The permit (PE 6603) allows for a maximum discharge of 5077 m3/day. The location of the discharge is 1 km upstream from the Duncan/North Cowichan sewage discharge.

The dilution of these discharges by the Cowichan River is important in determining their impact on water quality. Based on the Pollution Control Objectives for Municipal Waste Discharges, the preferred dilution of the sewage effluent is greater than 200:1. The theoretical minimum dilution ratios for the sewage discharges were calculated using the 1-in-2-year, 7-day average low flow for the Cowichan River and the average effluent discharges recorded in the low flow month (e.g., August or September). Using the above flow and discharge rates, the dilution ratios of the Village of Lake Cowichan and the Duncan/North Cowichan effluents are 330:1 and 68:1, respectively. Assuming the maximum permitted discharge of PE 1497 (13000 m3/day) the dilution ratio for the Duncan/North Cowichan effluent would be 33:1.

There are public wharves, a small abandoned mine and an operational sawmill upstream from the Cowichan River which may also impact the water quality of the river. Cowichan Copper (also known as Blue Grouse) was a base metal mine within the Cowichan Lake watershed. The mine site is not a source of metals to the system at this time. The public wharves are a potential source of copper from anti-fouling paints. Microbiological contamination is possible from boats without septic holding tanks. The sawmill operated by BC Forest Products at Youbou may discharge anti-sapstain compounds which are potentially toxic to fish. Water quality objectives are set at the outlet of Cowichan Lake to protect the water uses of the Cowichan River from contaminants produced from these sources.

The Koksilah River does not have any permitted discharges; however, nonpoint nutrient and bacteriological contamination from dairy farms adjacent to Dougan Lake and runoff from the Cowichan Valley Regional District incinerator/landfill and gravel washing operations near Duncan, are potential sources of contaminants to the Koksilah River.

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WATER QUALITY

The general water quality of the Cowichan River is typical of rivers on Vancouver Island. High precipitation in the watershed causes very soft water that is low in colour and nutrients. In the upper reaches of the Cowichan River the water is low in turbidity and suspended residues. The lower reaches of the Cowichan River can have elevated turbidity during high river flow due to the erosion of till deposits adjacent to the river. The Koksilah River is similar to the Cowichan River in general water quality; however, turbidity levels may be higher due to the absence of a large headwater lake to act as a sediment trap.

Coliform bacteria are frequently detected at the outlet of Cowichan Lake and in the Koksilah River at the highway. The source of the fecal coliform contamination has not been determined.

Metals data have been collected on the Cowichan and Koksilah rivers for several years. Total copper, lead and, to a lesser extent, mercury and zinc are frequently detected in the Cowichan River near Riverbottom Road and the highway bridge, and in the Koksilah River at the highway. The concentrations of the above metals are generally low, with higher concentrations occurring during the winter months when stream flows are higher.

The impact of permitted discharges on the water quality of the Cowichan River is variable. The impact of the discharge from the Ministry of Environment fish hatchery is minimal throughout the year because of the low concentrations of nitrogen and phosphorus in the effluent. The impact of the effluent from the Village of Lake Cowichan is considered minor because of the high degree of dilution during the critical summer low flow period.

The discharge from the Duncan/North Cowichan sewage treatment facility has a detectable impact on the water quality of the Cowichan River. Fecal coliform concentrations remain low downstream from the discharge because of the adequate chlkorination and dilution. However, the low dilution ratio in the summer can cause minor increases in turbidity and suspended residues and significant increases in ammonia-nitrogen and dissolved phosphorus. The high nutrient loading causes excessive periphyton growth for several kilometers downstream from the discharge. The excessive periphyton growth can ionterfere with spawning salmonids, increase intra-gravel biological oxygen demand or decrease intragravel oxygen concentration thereby affecting incubating fish eggs or the benthic community. High ammonia nitrogen concentrations can cause an avoidance reaction or be toxic to fish.

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WATER QUALITY OBJECTIVES

Water quality objectives are established to protect the most sensitive water uses of the Cowichan and Koksilah rivers and are summarized in Table 1, Table 3 and Table 4.

The objectives are based on working criteria for water quality and on available data on ambient water quality, waste discharges, water uses and limnological characteristics. Some objectives will be provisional until the water quality monitoring programs provide adequate data and the Ministry has established approved water quality criteria for the characteristics of concern.

Water quality objectives have no legal standing and are not directly enforced. The objectives should be considered as policy guidelines for resource managers to protect water uses in specified water bodies. They will guide the evaluation of water quality, the issuing of permits, licences and orders and the management of the fisheries and the Province's land base. They will also provide a reference against which the state of water quality in a particular water body can be checked and serve in making decisions on whether to initiate basin-wide water quality studies.

Depending on the circumstances, water quality objectives may already be met in a water body, or may describe water quality conditions which can be met in the future. To limit the scope of the work. objectives are only being prepared for waterbodies and for water quality characteristics which may be affected by man's activity, now and in the future.

It is proposed that the following uses, not necessarily in order of importance, be adopted as the designated water uses to be protected in the rivers:

The water quality objectives outlined below are set to protect the most sensitive use. If the objectives are met for the most sensitive use, then all of the other uses of the rivers will be protected.

FECAL CONTAMINATION

Cowichan River
Bacteriological objectives are set for the Cowichan River based on the water use in a given reach. Above the Island Highway bridge the Cowichan River is used as a source of domestic water and primary-contact recreation (fishing and kayaking). The most sensitive use for this section of the river is domestic water use. For any point in this reach, outside initial dilution zones of effluents, the following bacteriological objectives shall apply:
the fecal coliform and Escherichia coli densities shall not exceed 10 cells/100 mL, and the enterococci density shall not exceed 3 cells/100 mL in 90% of at least 5 weekly samples taken at any point within a 30-day period. The objective is based on the Ministry of Health guidelines for drinking water supplies (that require only chlorination or equivalent) and on the Ministry of Environment water quality criteria for microbiological indicators.
Within the Cowichan Band Indian Reserve there are no domestic water users; however, the Cowichan Band uses the river to catch fish. This use is considered equivalent to secondary-contact recreation. The bacteriological objectives for this reach of the Cowichan River (from the Island Highway bridge to the mouth outside initial dilution zones are:
the fecal coliform and Escherichia coli densities shall not exceed geometric means of 100 and 385 cells/100 mL, respectively, calculated from at least 5 weekly samples taken during a 30-day period. The objectives for this reach are based the Ministry of Environment water quality criteria for microbiological indicators.
Koksilah River
The Koksilah River has several domestic water intakes. There is potential bacterial contamination from septic tanks and nonpoint loading from dairy farms adjacent to Dougan Lake and Patrolas Creek. Consequently, a fecal coliform objective based on the Ministry of Health guidelines for water supplies that require only chlorination (or equivalent) shall apply. The objectives for the Koksilah River are:
the fecal coliform and Escherichia coli densities shall not exceed 10 cells/100 mL, and the enterococci density shall not exceed 3 cells/100 mL in 90% of at least 5 samples taken at any point within a 30-day period.

DISSOLVED OXYGEN

Adequate dissolved oxygen concentrations are essential to minimize the stress on the adult and juvenile salmonid populations in the Cowichan and Koksilah rivers. The water quality objectives for dissolved oxygen apply to any point in the rivers excluding the initial dilution zones of effluents; however, monitoring (as outlined in Table 2) should be concentrated above and below the sewage discharges on the Cowichan River. The objectives are:
  1. A minimum of 11.2 mg/L from October to May for the protection of "eyed" or hatched salmonid eggs,
  2. A minimum of 8 mg/L during the remainder of the year for the protection of alevins and juvenile salmonids.

SUSPENDED RESIDUES

The suspended residue concentrations in the Cowichan and Koksilah rivers are generally low (average of 1.5 and 2.5 mg/L, respectively). The permitted sewage discharges into the Cowichan River would theoretically increase the suspended residue concentrations by 0.5 mg/L immediately outside the initial dilution zones during low flow.

The impact of the gravel washing operations adjacent to the Koksilah River near Duncan is not known, but they are potential sources of suspended residues to the Koksilah River.

The suspended residue objective for the Cowichan and Koksilah rivers outside initial dilution zones is:

not more than a 10 mg/L increase if background concentrations are less than 100 mg/L, or not more than a 10 percent increase if background concentrations are greater than 100 mg/L.

TURBIDITY

Turbidity is an important aesthetic characteristic for drinking water. For aquatic life, turbidity can limit light penetration and primary productivity. The turbidity objedtive is set due to possible impacts from the sewage discharges, the gravel washing operations or any other anthropogenic disturbances.

The turbidity objective for any point outside an initial dilution zone of a permitted discharge is:

if background turbidity levels are less than or equal to 50 NTU, the maximum increase should be less than or equal to 5 NTU; however, if background turbidity levels are greater than 50 NTU, the maximum increase should be less than or equal to 10% of background.

AMMONIA-NITROGEN

The un-ionized fraction of ammonia is the most toxic form of nitrogen to aquatic life. The amount of un-ionized ammonia is calculated from the total ammonia concentration, temperature and pH. The theoretical concentration of total ammonia outside the initial dilution zone of the Duncan/North Cowichan sewage discharge during the 1-in-2-year, 7-day low flow can approach 0.600 mg/L. Although the pH and temperature of the Cowichan River during low flow vary from point to point and year to year, the theoretical total ammonia concentration is very close to the average 30-day criterion for the protection of aquatic life, as determined in Table 3. Because the toxicity of ammonia increases with increasing pH and temperature, the maximum and 30-day average ammonia objectives for the Cowichan River outside the Duncan/North Cowichan initial dilution zone will vary. Average and maximum ammonia objectives are outlined in Table 3 and Table 4.

CHLOROPHYLL-a

Excessive periphyton growth can occur several kilometers downstream from a sewage treatment plant discharge because of the high concentration of nitrogen and phosphorus in the effluent. High levels of periphyton can be aesthetically displeasing and can impair fish reproduction through the reduction of intragravel water flow and dissolved oxygen. Chlorophyll-a measurements are frequently used to measure periphyon biomass.

The Cowichan River downstream from the Duncan/North Cowichan sewage treatment discharge is used by the Cowichan Indian Band for salmon fishing. This activity is considered to require the same protection as secondary-contact recreation; consequently, a chlorophyll-a objective of 50 mg/m2 for aesthetics is used for the Cowichan River downstream from the Village of Lake Cowichan and the Duncan/North Cowichan sewage discharges beyond the initial dilution zones.

TOTAL RESIDUAL CHLORINE

Chlorine is commonly used to disinfect effluents from sewage treatment plants. After such disinfection, a family of reactive chemicals called 'total residual chlorine' is produced. Since this 'total residual chlorine' is highly toxic to aquatic life even at concentrations below those measurable by present-day technology, these chemicals must be removed from effluents being discharged to particularly sensitive environments. Trout and salmon are recognized as being especially sensitive to 'total residual chlorine'. Removal of these chemicals is referred to as dechlorination, and is usually accomplished through reaction of the 'total residual chlorine' with a reducinf agent such as sulphur dioxide. Dechlorination is required at both the Village of Lake Cowichan and the Duncan/North Cowichan sewage treatment plants because of the importance of the salmonid fishery within the Cowichan River.

A 'total residual chlorine' objective of 2 micrograms/L is set on the Cowichan River outside the initial dilution zones for the protection of aquatic life.

METALS

Detectable concentrations of total copper, total lead and total zinc have been measured consistently since 1986 in the Cowichan River and near the mouth of the Koksilah River. Since the sources of the metals may be anthropogenic in nature (i.e., old mine site, gravel washing operations, landfill, etc.), the following objectives will apply outside initial dilution zones for the protection of aquatic life:
dissolved metals 30-day average (mg/L) maximum concentration (mg/L)
copper 0.002 0.004
lead 0.003 0.008
zinc 0.030 0.180
The 30-day average is calculated from a minimum of 5 weekly samples collected in 30-days.
If background metal concentrations upstream from known sources exceed the above objectives, then anthropogenic impacts should not be allowed to elevate the ambient metal concentrations outside initial dilution zones by more than 20 percent above background concentrations.

The objectives are expressed as the dissolved fraction to avoid confusion with metals associated with suspended residues which frequently increase down the length of the rivers.

COPPER-8-QUINOLINOLATE

In the past, chlorophenols have been used as an antisapstain wood preservative by the BCFP sawmill at Youbou. Presently, the mill uses a new product: copper-8-quinolinolate (Cu-8). Because of the potential for this compound to enter Cowichan Lake and ultimately the Cowichan River, water quality objectives are required to protect the future fisheries resources of the Cowichan River. The water quality objective for Cu-8 at the headwaters of the Cowichan River is a maximum concentration of 0.0005 mg/L. The objective for Cu-8 must be regarded as provisional because of the limited data on environmental impact and toxicity.
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MONITORING RECOMMENDATIONS

A summary of the recommended water quality monitoring is given in Table 2. Monitoring is required to determine whether water quality objectives are being achieved and to provide ambient data to fill important data gaps.
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TABLES

Table 1. Ambient Water Quality Objectives for the Cowichan and Koksilah Rivers
Characteristics Cowichan River Koksilah River
Lake to Highway Highway to Mouth
Designated uses drinking, aquatic life, irrigation, industry, primary-contact recreation aquatic life, irrigation, secondary-contact recreation drinking, aquatic life, irrigation, industry, primary-contact recreation
fecal coliforms less than 10/100 mL
90 th percentile
not applicable less than 10/100 mL
90 th percentile
Escherichia coli less than 10/100 mL
90 th percentile
less than 385/100 mL
geometric mean
less than 10/100 mL
90 th percentile
enterococci less than 3/100 mL
90 th percentile
less than 100/100 mL
geometric mean
less than 3/100 mL
90 th percentile
turbidity -less than or equal to 5 NTU increase when background is less than or equal to 50 NTU
-less than or equal to 10% NTU increase when background is greater than 50 NTU
suspended residues -less than or equal to 10 mg/L increase when background is less than or equal to 100 mg/L
-less than or equal to 10% increase when background is greater than 100 mg/L
ammonia nitrogen AMMONIA TABLES not applicable
chlorophyll-a 50 mg/m2 maximum not applicable
total chlorine residual 0.002 mg/L maximum not applicable
dissolved oxygen -11.2 mg/L minimum from October to May
-8.0 mg/L minimum from June to September
dissolved copper -2 micrograms/L average
-4 micrograms/L maximum
-or 20% increase over background, whichever is greater
dissolved lead -3 micrograms/L average
-8 micrograms/L maximum
-or 20% increase over background, whichever is greater
dissolved zinc -30 micrograms/L average
-180 micrograms/L maximum
-or 20% increase over background, whichever is greater
copper-8-quinolinolate 0.5 micrograms/L maximum not applicable
Note: Objectives apply to discrete samples from all parts of the waterbody except from initial dilution zones of effluents. These excluded dilution zones are defined as extending 100 m downstream from the discharge point and no more than 50 percent across the width of the stream, from the surface to the bottom.
1. The fecal coliform, enterococci and Escherichia coli geometric means and 90th percentiles are calculated from at least 5 weekly samples taken in a period of 30-days. All bacteriological objectives apply on a year-round basis.
2. Since the chlorine residual objective is less than the minimum detectable concentration, it may be necessary to estimate the receiving water concentration using effluent loading and streamflow.
3. The ammonia nitrogen objective is an average of at least 5 weekly samples taken in a period of 30 days during low river flow.
4. The copper-8-quinolinolate is a provisional objective to be finalized when additional analysis by the Ministry of Environment has been completed.
5. The copper, lead, zinc, turbidity and suspended residues increase is over levels measured at a site upstream from a discharge or series of discharges and as close to them as possible, and applies to downstream levels.
6. The chlorophyll-a objective is based on the average from 5 to 10 individual samples collected on the same day outside the initial dilution zones. Natural substrates are to be used and, if the periphyon distribution is clumped, the percent cover of the community sampled must be noted.
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Table 2. Monitoring Schedule for the Cowichan and Koksilah Rivers
Sites Frequency and Timing Characteristics to be Measured
Cowichan River
E206108, 0120808, E206107, 0120801, 0120802, E206106
Koksilah River
E207425, E206976, 0123981
5 weekly samples over 30 days during low flow (generally August) and high flow (generally January) fecal coliforms, enterococci, Escherichia coli, (MF)
Cowichan River
0120808, E206107, 0120802, E206106
Koksilah River
E206976, 0123981
turbididty, suspended residues
Cowichan Lake (outlet)
0130180
Cowichan River
E206108
Koksilah River
0123981
dissolved copper, lead and zinc
Cowichan River
E206108
copper-8-quinolinolate
Cowichan River
0120808, E206107, 0120802, E206106
5 weekly samples over 30 days during low flow (generally August) dissolved oxygen, temperature
Cowichan River
E206107, E206106
ammonia nitrogen, field pH, temperature
5 to 10 individual samples collected on the same day during low flow (generally August) chlorophyll-a, phaeophytin, biomass, taxonomy sample
Duncan/North Cowichan sewage treatment facilities after dechlorination 5 weekly samples over 30 days during low flow (generally August) plus monthly samples total residual chlorine, discharge volume, stream flow
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Colin J. McKean, M. Sc., R.P.Bio.
Water Quality Branch
Environmental Protection Department
Ministry of Environment, Lands and Parks

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