Chapter 3.2 Water Quality and Stream Health
Relevant Port Phillip & Westernport Regional Catchment Objectives:RCS-WO4: Improve water quality in waterways, aquifers, wetlands, estuaries, bays and seas. Relevant Regional Targets:RCS-WT8: Improve water quality in rivers and streams so that: RCS-WT21: Improve water quality in estuaries, bays and seas so that all monitoring sites attain SEPP objectives or regional targets by 2030 RCS-WT22: Reduce the average annual nitrogen levels entering Port Phillip Bay by 1000 tonnes by 2006 RCS-WT24: Reduce the amount of litter and other gross pollutants entering Port Phillip Bay and Western Port by 70% by 2015 Relevant Regional Actions:RCS-WA10: Meet best practice standards in urban stormwater discharges in new urban areas RCS-WA17: Review and implement a surface and ground water quality monitoring system to ensure adequate and coordinated coverage across the region, including reservoirs, high discharge areas, bays and seas, high rainfall events and nutrient loads. RCS-WA44: Implement the Port Phillip Bay Environmental Management Plan to reduce the average annual nitrogen input into Port Phillip Bay by 1000 tonnes, and review and extend the plan to address additional risks to the Bay. RCS-WA47: Refine and implement key actions in municipal Stormwater Management Plans to reduce inputs of nutrients, toxicants and litter to the bays. |
Background
Legislation and Policy
The National Water Quality Management Strategy is implemented in Victoria through the Victorian River Health Strategy (VRHS) (Government of Victoria 2002) and the State Environment Protection Policy (SEPP) (Waters of Victoria) (WoV).
The Victorian River Health Strategy[223]provides a state-wide policy framework for managing the health of Victorias rivers.
State Environment Protection Policies (SEPPs) are the state-wide policy instrument for the protection of beneficial uses of water environments in Victoria. Beneficial uses are defined as the uses and values of the water environment that the community and Government want to protect.
Many factors affecting run-off quality and the health of waterways and the bays are not directly under Melbourne Waters control and require cooperative endeavours with Councils and landholders.
Stormwater quality is managed through a memorandum of understanding between Melbourne Water, EPA and the Municipal Association of Victoria. The agreement focuses on sharing accountabilities and costs for stormwater quality management between Melbourne Water and councils. Council stormwater management plans support the intent of the Urban Stormwater Best Practice Environmental Management Guidelines (CSIRO 1999). Meeting these Guidelines is now a statutory requirement for residential subdivisions under Clause 56 of state planning policy.
At a regional level, the Port Phillip and Westernport Regional Catchment Strategy (RCS) sets natural resource objectives, targets and programs, and identifies priorities for investment across land and water within the region. The Regional River Health Strategy is a strategy under the RCS that details river health objectives, targets and programs in the region. Targets include meeting the SEPP objectives for aquatic life. Overall River Health is assessed using the Index of River Condition (see below)
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INDEX OF RIVER CONDITION (IRC) The index of river condition is an integrated measure of environmental condition based on five sub-indices:
Assessments for each sub-index are based on one or more characteristics. Each sub-index is rated on a scale from 0-10. These ratings are then combined to produce the IRC which has a maximum value of 50. River condition is then identified on 1 -5 scale ranging from very poor to excellent. |
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Map 15 - SEPP Schedule F7 segments |
State Environment Protection Policy (SEPP) objectives for the Merri
The SEPP of relevance to the Merri is State Environment Protection Policy (Waters of Victoria), and in particular Schedule F7 Waters of the Yarra Catchment. This states the objectives required to protect beneficial uses of the Merri waterways. It has provisions binding on all individuals and organisations, government departments and agencies.
The SEPP identifies the upper Merri Catchment as belonging to the Rural Western Waterways segment and the lower catchment area as being part of the Urban Waterways segment.
The beneficial uses to be protected for each segment are at present identical. They are:
· maintenance of aquatic ecosystems and associated wildlife within modified ecosystems[224];
· passage of indigenous fish;
· maintenance of indigenous riparian vegetation;
· recreation (conditional primary contact e.g. swimming, secondary contact e.g. boating and fishing, and passive recreation);
· production of edible fish and crustacea;
· agricultural (and parks and gardens); and
· other commercial purposes (industrial water).
Schedule 7 to the SEPP establishes water quality objectives for each segment using various indicators.
Physico-chemical indicators of environmental quality include temperature, pH (acidity/ alkalinity), salinity, dissolved oxygen, turbidity, suspended solids, toxicants[225], taints, E. coli organisms, coprostanol (a faecal sterol which can distinguish faecal contamination of human origin from other sources) and nutrients (phosphorus and nitrogen).
Ecological indicators of environmental quality include the macroinvertebrate community (using the SIGNAL index score and other measures) and fish, based on presence of certain native fish species.
The SEPP objectives are based on the earlier version of SIGNAL (see Box). Use of SIGNAL 2 could provide more meaningful monitoring results for the Merri waterways although Pettigrove & Hoffman (2003b) have stated that SIGNAL is not suited for assessing the effects of toxicants on urban aquatic ecosystems. As discussed later, toxicants are a major problem in the Merri.
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SIGNAL INDEX The SIGNAL index (Stream Index Grade Number Average Level) for biological assessment of water quality allocates pollution sensitivity grades (scores 1 -10) to common Family level groups of macroinvertebrates (water bugs) found in streams. The score is calculated by summing the grades and dividing the total by the number of Families. The condition of a stream site is assessed according to ratings and placed in one of four categories ranging from clean water to probable severe pollution. A recent development of the SIGNAL index (SIGNAL 2) has produced a more versatile and reliable version of SIGNAL (Chessman 2003) which can respond to a range of forms of stream degradation. |
In addition Schedule 7 specifies that there must not be any litter, anthropogenic floatable materials, foams or scums, materials causing objectionable colours or odours, or visible films of oils, greases and petrochemical products or odours from such products.
The objectives for the urban segment are less stringent than the rural segment.
Also of relevance to the Merri waterways is the State Environment Protection Policy (Waters of Victoria) - Schedule F6 Waters of Port Phillip Bay which identifies nitrogen reduction objectives for the waterways entering the Bay. These objectives are specified in the Port Phillip Bay Environmental Management Plan and are based on the findings of the CSIRO Port Phillip Bay Environmental Study. This study found that the greatest threat to the health of the ecological process in the bay was increasing nitrogen, particularly from urbanisation of the catchment. Annual Bay Action Reports outline progress to meet these objectives and reduction in nitrogen loads to the Bay is a critical focus for the Better Bays and Waterways Water Quality Plan.
River Health Objectives for Merri waterways
The Regional River Health Strategy bases its assessment of river health and targets for future improvement on the Index of River Condition (IRC). IRC assessments were conducted for a total of 15 reaches in the Merri catchment - nine reaches on the Merri, one on Kalkallo Creek, one on Malcolm Creek, one on Aitken Creek, two on Edgars Creek and one on Central Creek[226].
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The objectives in the Regional River Health Strategy for the Merri are: For rural sections: Prevent further damage in the condition of rural sections, i.e. maintain at current overall condition of poor. IRC ratings for sub-indices are:
For urban sections: Within 5 years[227] improve the overall condition of urban sections from very poor to poor. Targets for IRC sub-indices are:
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Regional Water Quality Improvement Plan
A Regional Water Quality Improvement Plan, Better Bays & Waterways, is due to be completed by the end of 2008. It will identify and address risks to environmental values of Port Phillip and Westernport Bays and waterways and provide direction for investment in water quality improvement.
Waterways Water Quality Strategy
Melbourne Waters Waterways Water Quality Strategy (2008) is specifically for waterways. It sets the following ten year resource condition targets:
· Significantly counteract the effects of growth in greater Melbourne and achieve a net reduction in pollutant loads for the Port Phillip & Western Port region from 2001 levels;
· 80 per cent of monitoring sites meeting SEPP objectives or regional targets established through the Better Bays and Waterways Plan of action;
· Achieve a net reduction in effective imperviousness[228] from 2007 levels;
· Achieve specific water quality targets for rivers and creeks set out in the RRHS and the Victorian Ten Year River Health Plan.
Water Quality and Stream Health Studies of Merri waterways
In the wider Port Phillip and Western Port catchment urban areas contribute disproportionately to poor water quality. For example urban areas occupy about 27 per cent of the regional catchment yet account for 73 per cent of the nitrogen load. For example urban areas occupy 19% of the Port Phillip Catchment, but they contribute 42% of the catchment's nitrogen load (Melbourne Water: Better Bays and Waterways 2009).
The Merri catchment is no different. Changes in water quality along Merri Creek tend to be related to changes in land use.
Rural sections of the Merri Creek are generally healthier than the industrial and urban sections, although they still suffer from a range of problems most notably high nutrient levels and water quality is rated poor (see Box above).
Industrial areas generate high levels of heavy metal pollution and other toxicants. Problems in urban areas are primarily the result of the poor quality of stormwater which, except in newer residential areas, receives no treatment before discharge into the waterways. Water quality in urban sections is rated very poor (see Box above).
Studies of the water quality of Merri waterways have been reviewed and summarised by Amenta (2003), Condina (2003), McGuckin (2002) and Miller (2003). There is general agreement that water quality problems in the Merri system include:
· high levels of heavy metals in the sediments of both Merri and Edgars Creeks as a result of contaminated stormwater from industrial areas; leachates from tip and former tip sites probably also contribute to this problem;
· high concentrations of nutrients throughout Merri Creek, with the Craigieburn Sewage Treatment Plant (STP) a major single source; stormwater runoff, both urban and rural, is also a significant source of nutrients;
· organic pollution still affects parts of Merri and Edgars Creeks;
· salinity levels in parts of the Merri Creek often exceed the SEPP objectives, particularly in rural areas. It is not known if this is a natural feature of the catchment or a result of induced salinity. Stormwater inflows and the STP effluent dilute the salinity in urban areas;
· turbidity and suspended solids periodically exceed SEPP objectives after storm events;
· low levels of dissolved oxygen are a problem at times in rural sections, with lack of stream flow contributing to this problem;
· Edwardes Lake, on Edgars Creek, acts as a sink, trapping pollutants such as nutrients, heavy metals, sediments and toxicants, as well as rubbish;
· Litter has a marked impact on environmental values and aesthetic amenity of urban reaches of the Merri waterways.
Examination of water quality records over the past twenty five years suggest there has been some improvement in water quality in Merri Creek, particularly a reduction in organic pollution, most likely due to the sewering of outer urban areas. Some reduction in total phosphorus levels appears to have also occurred (McGuckin 2002).
However a study in 2000 found there had been no discernable improvement in conditions for aquatic life over the previous ten years (see below).
In-stream biological health
The earliest biological sampling of the Merri Creek took place in 1974 (Public Interest Research Group [PIRG], 1975). It showed a marked deterioration in macroinvertebrate species abundance and diversity downstream of Mahoneys Road, Fawkner.
More recent studies have drawn similar conclusions. In 1990 Mitchell and Clark conducted a comprehensive macroinvertebrate study. They showed a major decline in macroinvertebrate condition beginning downstream of OHerns Road Somerton with a sharp decline beyond Barry Road, Campbellfield.
A study by AWT (2000) ten years later found there had been few changes to the macroinvertebrate fauna assemblage since the 1990 study and could find no discernable improvement in aquatic life. SIGNAL scores were below SEPP guidelines for all sites monitored.
AWT found the downstream decline in macroinvertebrates correlated closely with declining water quality, especially increases in heavy metal pollution within the water column and sediments.
A study by Ecowise (2005) in 2003-04 identified the same sharp decline in macroinvertebrate health at site slightly downstream of the Ainslie Rd drain compared to sites upstream of Cooper Street.
Elegant field-based experiments by Pettigrove and Hoffman (2005) have demonstrated that this decline in macroinvertebrate diversity and abundance is caused by the toxicity of sediments of the Merri Creek (rather than simply being associational).
Heavy metals and other contaminants
A 2000-2001 study of nine drains in the Merri Catchment identified drains receiving runoff from small to medium sized industries as contributing the highest levels of heavy metals (Pettigrove & Hoffman 2003c). For example, medium concentrations of zinc were from 10 to 100-fold higher in drains from industrial sub-catchments compared to drains from residential sub-catchment.
The vast majority of samples collected in the study exceeded guidelines[229] for one or more metals. For many of the drains, average concentrations of heavy metals were consistently higher on workdays than Sundays, suggesting poor work practices are a key reason for heavy metal contamination.
Samples from the Barry Road Drain in Campbellfield showed the poorest compliance (100% of samples exceeded Zinc and Copper guidelines; 95% exceeded Nickel, 58% exceeded Lead, and 47% exceeded Chromium). Samples from the Ainslie Rd Drain, also in Campbellfield, showed a similar lack of compliance. Both these drains outfall to Merri Creek.
Samples from the Merrilands Drain in Reservoir and the Thomastown Drain, both on Edgars Creek, had between 80-100% of samples fail to comply with Zinc and Copper guidelines.
The Pettigrove and Hoffman (op.cit.) study also investigated the longitudinal profiles of heavy metal concentrations in creek sediments. Substantial increases in sediment concentrations of Zinc and Copper were found in Merri Creek downstream of the Ainslie Rd and Barry Rd drains, corresponding well with the dry weather discharges from these drains.
Of considerable relevance to the Merri is the finding by Pettigrove and Hoffman (2003) that heavy metals tend to reach levels of concern at lower levels of urbanisation (as indicated by percent catchment imperviousness) in streams with soils derived from basaltic rather than sedimentary materials. They suggest this may be related to the different characteristics of water chemistry and sediment size in basalt streams and conclude that &a greater emphasis should be placed on heavy metal management in basalt rather than in sedimentary streams.
In a separate study, Pettigrove and Hoffman (2005) found that high-molecular weight hydrocarbons derived from crude oil (gasoline, kerosene, fuel oil, mineral oil and asphalt) are a significant pollutant in urban water bodies and have an adverse effect on macroinvertebrates.
The primary effects are through smothering and mechanical interference with activities such as movement and feeding. About 28% of water bodies surveyed in Melbourne had total petroleum hydrocarbon (TPH) concentrations in sediments likely to cause ecological impairment. Merri sites are likely to be at least as bad as the Melbourne average. The authors concluded that freshwater sediment quality guidelines need to be developed for this ubiquitous urban pollutant.
Little study has been done of pesticides (this term includes herbicides, fungicides, insecticides, rodenticides etc), in the water or sediments of the waterways of the Merri catchment. Through Melbourne Waters Research and Technology team, research and monitoring programs are expected begin soon to detect sediment toxicity and measure pesticides, heavy metals and petroleum hydrocarbon concentrations in sediments.[230]
Minimisation of herbicide use is discussed in chapter 2.3 Land Management.
As noted earlier, contaminants from stormwater drains, particularly the Barry Rd and Ainslie Rd drains, have been shown to have a serious impact on the macroinvertebrate fauna of the Merri. Of further concern is the downstream movement of toxicants in sediments, with heavy rains flushing sediments from the Merri into the Yarra and thence to Port Phillip Bay.
Impact of Craigieburn Sewage Treatment Plant
The only significant licensed discharge to Merri Creek is that of treated effluent from the Craigieburn Sewage Treatment Plant (STP). A biomonitoring program for 2003-2004 (Ecowise 2005) identified statistically significant increases in phosphorus, nitrogen, nitrate, nitrite and ammonia, total Kjeldahl nitrogen and water temperature attributable to the STP and statistically significant decreases in electrical conductivity, dissolved oxygen, suspended solids and E. coli.
Breaches of SEPP objectives attributable to STP discharge were detected in total phosphorus, total nitrogen, dissolved oxygen and water temperature. Breaches of ANZECC (2000) toxicant trigger values were detected in ammonia and nitrate concentrations.
For most of the nutrient parameters the extent of the mixing zone[231] varied between 15m to 1km downstream from the discharge. Other water quality parameters had mixing zones up to 150m downstream.
SIGNAL scores generally decreased downstream of the discharge, demonstrating the impact of the effluent discharge on the macroinvertebrates. However in the dry year of 2003, when natural flow in Merri Creek was low, the permanent STP discharge functioned as an environmental flow, allowing sites downstream of the discharge to function as refugia for aquatic organisms. In 2004 when the natural stream flow in Merri Creek was greater, the permanent flow of the STP did not provide the same function and macroinvertebrate health was better upstream than downstream of the discharge. In both years assemblages of macroinvertebrates that were collected downstream of the discharge point were different to those collected upstream of the discharge point.
The Ecowise report concluded that:
The water quality impacts that are having the greatest impact on the ecological health of Merri Creek are nutrient enrichment, water temperature increases (28% increase) and dissolved oxygen depletion. Nutrient enrichment of Merri Creek is promoting the growth of macrophytes and algae immediately downstream of the discharge point, which is encouraging the dominance of macroinvertebrates that feed on these plants.
Although the Craigieburn STP discharge did in effect provide environmental flows, the significance of the ecological benefit to Merri Creek macroinvertebrates is negligible. (p.47)
Yarra Valley Water reported in December 2008 that the effluent discharge standard at the Craigieburn STP will be reviewed in light of their revised strategy to continue to operate the plant. Any proposed changes to the effluent quality will be determined in conjunction with EPA with due consideration to the environmental drivers. Yarra Valley Water added that it should be noted that the STP is currently operated in compliance with the existing EPA Waste Discharge Licence[232]
Pollution spills
Pollution spills are not uncommon on Merri Creek. Generally EPA responds by assessing the spill and may involve Melbourne Water in cleaning it up if that is practical. Enforcement is primarily EPAs responsibility.
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Photo 1 - A pollution spill in 2008 near Andersons Road |
Sometimes pollution is first reported to MCMC, whose procedure is to record the report, to encourage the person reporting the pollution to call EPA directly, and if possible to check out the event and assist EPA where possible. Councils have a similar role and procedure.
Pollution spills may be highly visible if they result in foaming or discolouration of the water, but not all spills are so visible.
When a spill is reported it is important that the person reporting the spill can identify unequivocally where the pollution is coming from. Darebin Creek Management Committee has arranged for every pipe outlet to be labelled using a system that EPA, Council and Melbourne Water can use to locate pipes. This system is not at present in place on Merri Creek.
Preventing spills and dealing with them when they happen deserves ongoing attention.
Faecal contamination[233]
A 1997 study by the EPA showed that faecal contamination was at times high in Merri Creek. High herbivore-associated contamination levels were attributed to grazing stock in the upper catchment, and occasionally high human faecal contamination levels due to sewer overflows.
Overflows of raw sewage to Merri and Edgars Creeks occur via emergency relief valve structures during high rainfall events as a result of stormwater entering the sewers and causing sewer capacity to be exceeded. This problem is being addressed by Melbourne Water and Yarra Valley Water through the Northern Suburbs Sewerage Strategy and involves construction of significant additional sewer capacity. Part of the Strategy, is the Northern Sewerage Project.
Once completed in 2012, the project will provide an unrestricted outlet for the major sewers in the northern suburbs. However in order to prevent overflows from all ERSs during rainfall events less than the 1 in 5 year standard, some additional localised upgrade works are still required. YVW has a capital works program in place to address these localised problems and intends to complete this work by 2017/18. At that stage the SEPP requirements, which specify sewerage infrastructure capable of containing flows associated with a 1-in-5-year rainfall event, will be met. During higher rainfall events sewage overflows may still occur.
More recent analysis has identified a number of stormwater drains which contribute faecal contamination to the creek even during periods of low flow. This suggests cross contamination between sewer pipes and stormwater drains is occurring, either through leakage or direct connections. Investigation and remedial action has been established as a high priority by the State Government through the Yarra River Action Plan (DES 2006).
Climate change and water quality
The implications of changing weather patterns on water quality are not yet well understood. For example more intense storms could increase the frequency of sewer overflows, and also lead to greater loads of pollutants bypassing stormwater treatment systems.[234]
On the other hand, reduced rainfall could lead to lesser loads of pollutants entering the stormwater system, but lower flows within the streams could lead to a build up in concentration of pollutants. Combined with higher temperatures this would lead to decreased levels of oxygen and problems of excessive algal growth (eutrophication).
MCMCs Waterwatch monitoring of the Merri has demonstrated some of these factors at work with monitoring in the dry summers of 2006 and 2007 showing some sites had higher levels of salinity and slightly higher levels of phosphate (a nutrient), as well as a visible increase in algal growth. Nevertheless simultaneously there were signs of some improvement in stream health apparently due to the reduction of stormwater runoff. This was illustrated by the occurrence of certain macroinvertebrates not previously seen when there were higher levels of stormwater runoff, due to higher rainfall.
Opportunities to Improve Water Quality
Rural Areas
The Wallan Sewage Treatment Plant (STP), commissioned in the late 1980s and now operated by Yarra Valley Water, is licensed by the EPA to discharge to land. In the past there have been concerns that its operation may generate runoff or cause contamination of groundwater which could be transported to Merri Creek. Beardsell reported that water quality in the Bald Hill area of Merri Creek had declined since the STPs commissioning (Beardsell, 1997, Vol. 2, p. 15), although there are no supporting studies to confirm these observations.
Since this time, the area of land available for effluent disposal has been expanded and according to Yarra Valley Water the Wallan STP continues to achieve 100% effluent reuse with no direct discharge to Merri Creek. Class C effluent is currently treated and stored in several large open dams (located at the STP site as well as on its nearby property in Beveridge) and used entirely for irrigation. All users have Environmental Improvement Plans in place to ensure the environment is not impacted in any way through irrigation. Additionally, YVW also conduct annual monitoring of groundwater quality as the Wallan STP site to detect any infiltration impacts from the operation of the STP.
By 2010, YVW plans to start using a portion of the effluent from the Wallan STP to produce Class A recycled water for supply to residential households in Beveridge and South Wallan. They state that this will ensure that the 100% reuse target can continue to be achieved into the future.
There is evidence that some sections of the stream are suffering water quality problems from rural runoff (see IRC assessment). Beardsell records the area around Hernes Swamp as one such example with algal blooms generated by enrichment from stock faeces causing eutrophication of the stream water during the summer (Beardsell, 1997, Vol. 2, p. 17).
Landholders are being encouraged to fence streams from stock grazing and thus reduce bank disturbance and organic pollution contributions. Melbourne Waters Stream Frontage Management Program assists rural landholders through grants to carry out fencing, weed control and revegetation of stream banks.
As identified in its Waterways Water Quality Strategy, Melbourne Water (2008) is developing a rural land management program in consultation with the Port Phillip and Western Port Catchment Management Authority and Department of Primary Industries to encourage the adoption of agricultural best management practices to improve rural run off. In places the program will also provide treatment facilities for rural runoff such as regional wetlands. The program will also integrate with the existing Stream Frontage Management Program to manage stock access and riparian vegetation where stock access is a threat to water quality.
Urban Growth Areas
Active development of land for residential and industrial purposes is occurring in the middle part of the Merri catchment, around Craigieburn and Epping. In the Craigieburn area this includes the Aitken, Malcolm, and Kalkallo Creek sub-catchments as well as the Merri itself. The development in Epping and North Epping falls within the Edgars and Central Creek sub-catchments.
There is also considerable growth occurring in the town of Wallan and in the vicinity of the township of Beveridge, in the upper catchment of the Merri beyond the metropolitan Melbourne urban growth boundary[235], The Wallan development has the potential to impact on Mittagong, Taylors, Wallan Creeks and Merri Creeks. Beveridge lies within part of the upper catchment of Kalkallo Creek.
Greenfields development sites present a significant opportunity to implement best practice stormwater treatment to minimise the extent to which water quality of the Merri system will decline. Increasingly, water sensitive urban design features, focused on structural measures at or near the source, are expected to play a key part in the achievement of water quality objectives.
The recent construction of the Craigieburn Bypass incorporated state of the art Water Sensitive Road Design incorporating sediment ponds, stormwater treatment wetlands and biofiltration trenches to ameliorate runoff from the freeway. Treated water is eventually directed into Edgars and Merri Creeks. Performance of these wetlands in the medium and long term needs to be monitored, as their effectiveness in the long term has not been demonstrated, and the minimum level of maintenance needed is uncertain.
The Victorian State Planning Provisions now require stormwater quality objectives to be met for all new Greenfield residential subdivisions. However there are still no requirements for industrial and commercial development or infill allotment scale residential development to meet these objectives.
Although a vast improvement on earlier practices, the application of current best practice stormwater objectives is not sufficient to prevent an increase in nutrient, suspended solids and toxicant loads.
The change in land use from rural grazing to urban typically leads to a net deterioration of water quality and adds to existing environmental risks. The Melbourne 2030 Hume Growth Area final report states that: Future urban growth must be premised on measures to achieve a net gain in stormwater quality discharging to waterways.(p.89).
In recognition of this Melbourne Waters Water Quality Strategy indicates that EPA Victoria may review and strengthen the stormwater quality objectives. The following implementation target is identified:
"New or revised State Government requirements for all industrial, commercial, residential development to meet best practice water quality objectives by 2013 (IT3)."
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Current Best Practice Stormwater Quality Objectives 80% reduction on suspended solids 45% reduction in total nitrogen 45% reduction in total phosphorus |
Adequate management and enforcement of controls during the construction phase of sub-division is an ongoing challenge. These activities are known to regularly contribute excessive amounts of suspended solids and other materials. Monitoring of Malcolm Creek in Craigieburn during construction of the Craigieburn Bypass showed excessively high suspended solids after rain events, apparently due to subdivision construction activity.
Established Urban Areas
As discussed earlier, contaminated stormwater runoff derived from poor work practices and illegal disposal of materials in industrial areas is known to be a continuing problem for the water quality of Merri and Edgars Creeks. This is in addition to the range of activities which generally contribute to poor water quality in residential urban areas. Within established urban area there are many diffuse sources of pollutants of stormwater and streams. Nutrient-containing detergents from street car-washing, road paving material, sediments, oils and other vehicle-sourced materials (e.g. brake linings), vegetative material, and litter of various types all contribute to the poor to very poor quality of water in urban streams.
It is also known that there are contributions to the stream from organic pollutants derived from sewerage. The Craigieburn Sewage Treatment Plant is a significant contributor of nutrients to the stream. Yarra Valley Water operates the STP in strict accordance with its EPA operating licence, which requires regular monitoring of effluent quality at both the plant and within the Merri Creek. Yarra Valley Water revised its strategy for the provision of sewerage services to the Craigieburn area in 2008 , resulting in the continued operations of the STP, and will be reviewing its effluent discharge standard as a result.
In existing urban areas opportunities for installation of off-stream wetlands to treat stormwater before discharge to urban streams have mostly been lost with intense land use for other purposes. One option for some water quality improvement lies in the creation of ephemeral wetlands in the floor of some retarding basins in the urban catchment. Such work has recently been undertaken by Melbourne Water in the Campbellfield Creek Retarding Basin[236] in Glenroy/Fawkner.
Smaller drains can be treated through rain gardens and wetlands such as that installed in 2007 adjacent to Merri Creek to treat stormwater for the Walker Street drain in Clifton Hill (2007). Another rain garden is planned for a nearby drain.
Raingardens have been established in the grounds of a number of schools, including Merri Creek Primary School in North Fitzroy, as part of Melbourne Waters program to develop 10,000 rain gardens in community facilities by 2013 (Waterways Water Quality Strategy IT9).
There is considerable potential for stormwater quality improvement through adoption of WSUD in existing urban areas, as described in a study undertaken for the Association of Bayside Municipalities (2004). This study demonstrated the potential for achievement of improved stormwater quality, even at a single lot level, through use of water tanks, and infiltration techniques such as porous pavements and bioretention rain gardens.
Redevelopment and infill development of existing urban areas provides opportunities to implement such measures through planning permit provisions.
Recent scenario testing for Melbourne Waters Water Quality Strategy (URS 2006) explored the ability of WSUD (biofilters for road runoff, water tanks for roof runoff, and end of catchment stormwater treatment) to improve stream health and attainment of SEPP objectives. In summary, in inner and middle urban areas reduction of effective imperviousness to five percent (the percentage required to achieve significant stream health improvements) is very difficult to achieve and requires greater than 70% of the catchment area being treated. Significant increases in revenue would be needed to do this. The most effective strategy for reducing pollutant loads was shown to be through the treatment of road runoff. However this in itself would not lead to achievement of SEPP objectives.
The Waterways Water Quality Strategy links the focus on road runoff to Councils renewal of roads and drainage and commits Melbourne Water to working with Councils to integrate WSUD into planned road renewals. The recent renewal of a section of Martin Street in Thornbury with street tree rain gardens is an example.
However this focus lacks a strategic link to prioritise those roads which generate the most polluted runoff. These are likely to be the busiest roads and roads in industrial areas.
Although short term opportunities to make dramatic improvements to the overall water quality of streams in urban areas are limited, significant improvements to stormwater from industrial areas could be made quite readily. Given the level of impact, industrial stormwater should be a high priority.
Further research on the treatment of stormwater containing toxicants has been identified by Pettigrove & Hoffman (2003) who state that There is little information regarding the efficacy of artificial wetlands in the GMA [Greater Melbourne Area] in treating common urban toxicants.
A recent trial of a toxicant treatment facility on the notorious Barry Road Drain, Campbellfield, demonstrated that significant reductions in hydrocarbon and heavy metal pollution can be achieved by passive filtration with affordable, locally available materials (Marshall et al 2006).
There is also considerable scope for specific structural measures at individual premises and for improvements in layout of industrial premises, particularly the complete isolation of work areas from the stormwater system with all runoff from work areas being directed to sewer. This latter approach is that taken by the (draft) Hume Industrial Stormwater Code of Practice (2008) which proposes such measures be a requirement of planning permits. It also proposes the use of WSUD at individual lot level to treat all stormwater generated from the on-work areas e.g. roofs and car-parks. This solution is ideal for new premises but there is no regulatory ability to require this for existing premises.
The potential for intensive educative programs to assist in improving small industry operators to understand causes of industrial stormwater pollution, and to implement practices to mitigate pollution, has been demonstrated by Hume Councils Merri Creek Industrial Stormwater Project (2005) and MCMCs Catching On projects. Recommendations from the Hume 2005 Project led to the Hume Industrial Stormwater Code of Practice which in addition to the planning regulations covering layout and WSUD requirements (mentioned in the previous paragraph) includes proposals for:
· Education & Information: detailed stormwater behaviour and operational information for specific industry types;
· Engagement: ongoing Council support information and enforcement program.
Litter
Litter has long been recognised as a significant issue for urban waterways. It detracts from the visual appearance of stream environments, is a health hazard, poses threats to fauna, and can cause blockages to drainage systems causing local flooding. After water quality it is the issue of most concern to Merri Creek Parkland users (see Table 13 on page150)
Legislation and Policy
The Victorian Litter Action Alliance (VLAA), formed in 2000, is the peak body for litter management and prevention in Victoria and aims to provide a coordinated approach to preventing litter in Victoria across state and local government, industry and community sectors. Its membership includes state and local government organisations and key industry sector representation.
In 2005 the state government released its Sustainability in Action: Towards Zero Waste Strategy which targeted a 25% reduction of litter and littering behaviour to be achieved by 2014.
In 2006 the state governments Our Environment Our Future Sustainability Action Statement identified the need to develop a new litter strategy to replace the 1995 Litter Reduction Strategy (EPA 1995b). The new litter strategy for Victoria is being developed by Sustainability Victoria in partnership with the EPA and the Department of Sustainability & Environment. The draft is due for release in 2008. This follows release of a Litter Strategy Background Paper, a Litter Strategy Issues Paper (VLAA & SV 2007) and a public consultation process.
Local governments play a central role in litter management through provision of:
· infrastructure - litter bins, litter traps, street cleaning;
· education - running targeted litter prevention programs; and
· enforcement - implementing the litter provisions of the Environment Protection Act 1970 Part VIIA.
A number of local governments have developed municipal litter strategies (e.g. Moreland City Councils Waste and Litter Strategy 2006-2011) or are part of a regional strategy under the auspice of their regional waste management group (RWMG).
Studies of Litter
Over the years various studies have been undertaken of the types and distribution of litter in Victoria. A systematic methodology to identify litter hotspots those areas that generate the greatest volume of litter using GIS available data has recently been undertaken by Melbourne Water for the lower Yarra (Catchlove and Francey 2007). Hotspots lie predominantly in commercial areas and in the vicinity of food markets and are influenced by transient populations. Trialling of intervention strategies at these hotspots will provide important information for tackling all hotspots over time.
Numerous other studies have included analysis of littering behaviour, attitudes and perception, and actions comparing bin use with littering (VLAA Litter Strategy Issues Paper).
Cigarette butts are the most littered item in Victoria and have been since 1997 when they were first included in counts, followed by beverage containers, paper, organics and chewing gum (Victorian Litter Report 2005). Illegal dumping is also a major litter problem.
Merri Creek was the first stream in the Melbourne area to have a study of its litter problem. The pilot study (Leighty, 1989) found that 66% of total human-sourced litter collected was plastic based, 21% of which were plastic bags. [cigarette butts were not counted in this study]
The Merri Creek study also discovered that considerable volumes of litter, (mainly plastics), were contributed from industrial areas, especially within the Merlynston Creek catchment (ibid, p. 28).
A further important study of litter in the Merri catchment occurred through the trial of the Pollutec (now CDS) litter trap located at McCrory Street, Coburg. This is a continuous deflective separation type trap constructed alongside the 1200mm Harding Street Main Drain. Analysis of the trapped material showed that more than two-thirds of the load was vegetation. Personal litter (plastics and paper) made up most of the remainder of the load (Allison, Wong and McMahon, 1996).
The most recent study of litter in the Merri, though now more than a decade old, is one which focussed on the contribution of Free Advertising Material (FAM) to the litter stream (Murfitt & Le Couteur 1997). It studied an area of approximately 50 hectares in central Coburg which included much of the shopping area of Sydney Road and Waterfield Street. The study found that FAM was the dominant source of paper litter in the residential parts of the study area, comprising between 20% and 52% of the total paper litter. In commercial parts of the study area, as a percentage, FAM was a less significant litter contributor (ibid, p. 25).
In the case of Merri Creek the stream retains the majority of the larger litter items transferred to it, mainly due to the vegetation cover along the stream. While this provides a degree of benefit in that litter is not transferred to Port Phillip Bay, the litter trapping capacity of stream vegetation becomes an obvious visual problem.
Actions on litter
Over the years there has been increased focus on stopping litter at the source and in building the skills of local government to implement best practice litter prevention programs. A range of initiatives have been implemented in various parts of Victoria these are detailed in the VLAAs Litter Strategy Background Paper.
Structural improvements for litter trapping in the Merri
In addition to specific improvements made by Councils in the provision of bins and litter collection services (especially closed-bin recycling collections) some major litter traps have been installed in the Merri Creek catchment in recent years.
Melbourne Waters litter trap on the main stem of Merri Creek at Rushall Reserve was removed several years ago, but more recently it installed a boom type (Bandelong) litter trap in Merri Creek itself just before its confluence with the Yarra.
Melbourne Water constructed a litter trap on the Preston Main Drain (within Northcote Golf course) in 2003 and there are three other gross pollutant traps in Darebin on Edgars Creek. Two are at the Leamington Street Wetland and one at Edwardes Park Lake. The design might be improved, however they have stopped huge volumes of litter and organic matter from entering Edwardes Park Lake, and the Merri Creek.
Maintenance of these traps is Melbourne Waters responsibility. In high flow events a bypass system comes into effect, meaning that litter is no longer trapped.
Moreland has installed Pollutec litter traps on the Albion Street drain and on the Harding Street Main Drain[237] near the Upfield railway line.
Mitchell Shire Council installed a litter trap on Wallan Creek in 2005. A small litter trap was developed by MCMC in 1996 for a council drain in Moreland at Victoria Street in Phillips Reserve and is now being maintained under contract to Moreland Council.
In various places Councils have installed grid- type litter traps on the side entry pits of the street level stormwater collection system.
New subdivisions
For a number of years all new subdivisions have been required to have in place mechanisms to deal with litter (gross pollutants) as part of the requirements for meeting urban stormwater quality standards (see earlier section).
Whilst local Councils and Melbourne Water have inventories of their litter trap assets there is no systematic mapping of the locations of litter traps across the catchment or identification of the extent to which litter hotspots are being treated.
Education initiatives in the Merri
In addition to numerous Council-based initiatives, Merri Creek Management Committee, in conjunction with a range of project partners, has placed considerable resources into a variety of programs to address community education about litter. Projects with local schools, Sydney Road traders and at Preston Market have been conducted by MCMC in recent years[238]
The Edwardes Lake Neighbourhood Environment Improvement Program has also had an emphasis on litter reduction and a Say No to Plastic Bags campaign is planned as part of the NEIP in October 2008, to be focused on the Reservoir Shopping Centre.
Cigarette butt litter grants from Sustainability Victoria in 2006 and 2007 have provided funding to MCMC to tackle the lack of information and understanding of the problems and penalties associated with cigarette butt littering in culturally and linguistically diverse CALD communities.
The importance of communicating directly to CALD groups was similarly recognised in the Lower Yarra Litter Strategys Victoria Street (Richmond) project, the success of which was enhanced by ensuring that the audit of trader practices and knowledge was undertaken in Vietnamese (VLAA newsletter The Lower Yarra Litter Strategy Hits Litter Hard!).
In terms of dumping, a new kit from the Victorian Litter Action Alliance Illegal Dumping Kit People at Home[239]is designed for agencies or organisations to help them reduce rubbish dumping.
Litter cleanups
For many years the Friends of Merri Creek have been active in organising regular litter collection efforts along the urban sections of the creek, usually on a monthly basis. The Friends of Malcolm Creek, formed in 2007 had their first litter clean up in this same year, as did the Friends of Edgars Creek.
The Adopt-a-Lake group, based at Edwardes Lake, Reservoir (on Edgars Creek) conducts at least nine litter clean ups per year. The annual Clean Up Australia Day regularly attracts efforts at various sites along Merri Creek.
The development of a Litter Strategy for the waterways of the Merri catchment is needed. It should address identification of litter hotspots and priority treatment of identified problem areas using the well established three critical elements to changing littering behaviours education, infrastructure and enforcement.
Key References
ABM (2004) Delivering Water Sensitive urban design. Final report of Clean Stormwater a planning framework. Association of Bayside Municipalities.
Amenta V. (2002) Summary of water quality and stream health monitoring data. Appendix 2 Part B, Merri Creek Waterway Management Activity Plan (Final Draft), Melbourne Water.
Bate, N., Hewlett, R. Leeming, R. and Reed, J. (1997) Origins of Faecal Contamination of the Lower Yarra River an Investigation using Faecal Sterols and Bacteria, Publication 538, Environment Protection Authority, Victoria, Melbourne.
Catchlove, R. and Francey, M. (2007) Hotspots a methodology for identifying, prioritising and tackling litter in urban environments.
Chessman, B. (2003) SIGNAL 2.iv A Scoring System for Macroinvertebrates (water bugs) in Australian Rivers. User manual. Monitoring River Health Initiative Technical Report Number 31, Department of the Environment and Heritage, Canberra.
Condina, P. (2003) Summary of Water Quality and Stream Health Issues. Appendix 2 Part A, Merri Creek Waterway Management Activity Plan (Final draft) Melbourne Water.
CSIRO (1999) Urban Stormwater Best Practice Environmental Management Guidelines.
Dept of Sustainability and Environment (2006) Yarra River Action Plan
Dept of Sustainability and Environment (2006) Strengthening the Management of the Yarra and Maribyrnong Rivers A background report for future water quality management
Ecowise Environmental Pty Ltd (2005) Biomonitoring the effects of Craigieburn STP effluent discharge on Merri Creek 2003-2004. Report submitted to Yarra Valley Water.
Environment Protection Authority, (1995b), Victoria's Litter Reduction Strategy, Government of Victoria, Melbourne.
Government of Victoria (2004) Our Water Our Future, Securing Our Water Future Together, Victorian Government White Paper, Department of Sustainability and Environment, Melbourne.
Government of Victoria (2003) State Environment Protection Policy (Waters of Victoria).
Government of Victoria (2002) Victorian River Health Strategy, Department of Sustainability and Environment, Melbourne.
Government of Victoria (1999) State Environment Protection Policy (Waters of Victoria) Schedule F7. Waters of the Yarra Catchment.
Victorian Litter Action Alliance (
Marshall, S., Pettigrove, V. and Kearns, J. (2006) A toxicant treatment facility for the field evaluation of filtration media for urban stormwater treatment. Poster Paper presented at 7th UDM & 4th WSUD, Melbourne.
Melbourne Water (2008) Waterways Water Quality Strategy
Murfitt, P. and Le Couteur, J. (1997). The Litter on our Streets. A Study of an Urban Catchment to Help Reduce Litter, Moreland City Council and Merri Creek Management Committee, Melbourne.
Pettigrove V. and Hoffman, A. (2003) Impact of urbanisation on heavy metal contamination in urban stream sediments: influence of catchment geology. Australasian Journal of Ecotoxicology 9, 119-128.
Pettigrove, V. and Hoffman, A. (2003b) Toxicants in Melbournes streams and wetlands: an emerging threat to healthy aquatic ecosystems. Proceedings: Australian Water Association Conference Perth, Western Australia, April.
Pettigrove, V. and Hoffman, A. (2003c) Major sources of heavy metal pollution during base flows from sewered urban catchments in the City of Melbourne. Proceedings, 3rd South Pacific Conference on Stormwater and Aquatic Resource Protection combined with 10th Annual Conference of the Australasian Chapter of the International Erosion Control Association, Auckland, New Zealand, New Zealand Water and Wastes Association, May 14-16, 2003 CDROM
Pettigrove, V. and Hoffman, A. (2005) A field-based microcosm method to assess the effects of polluted urban stream sediments on aquatic macroinvertebrates. Environmental Toxicology and Chemistry 24(1), 170-180. .
Victorian Litter Action Alliance and Sustainability Victoria (2007) Litter Strategy Issues Paper
Issues
1. Many SEPP targets are not met in the Merri waterways.
2. Water quality in urban areas of the Merri Catchment is very poor and in rural areas is poor.
3. Greater emphasis should be placed on heavy metal management in basalt rather than sedimentary streams.
4. Freshwater sediment quality guidelines need to be developed for total petroleum hydrocarbons.
5. The Craigieburn Sewage Treatment Plant discharge impacts on Merri Creek in complex ways; negative impacts include nutrient enrichment, water temperature increases and dissolved oxygen depletion, whereas the benefit of its environmental flow On invertebrates is negligible.
6. A system uniquely identifying discharge points would assist in spill reporting and response.
7. Preventing pollution spills and dealing with them when they happen is still important.
8. Faecal contamination in Merri Creek is at times high. Emergency sewer overflows will become rarer when the Northern Sewerage Strategy is implemented, but some stormwater drains contribute faecal contamination during dry weather.
9. The impacts of climate change on Merri waterways are not well understood.
10. Grazing contributes to poor water quality in rural sections of the catchment. This can be addressed by fencing off waterways and revegetating banks. In some areas regional wetlands for treatment of rural run-off may be needed.
11. Residential, commercial and industrial development in the northern part of the catchment will lead to degradation of waterways unless higher standards are established for stormwater treatment.
12. Long term monitoring of the effectiveness of wetlands is needed to identify required levels of maintenance.
13. Future urban growth must be premised on measures to achieve a net gain in stormwater quality discharging to waterways.
14. Subdivision construction activities regularly contribute excessive amounts of suspended solids and other materials, requiring improved management and enforcement of sediment controls.
15. There is potential for more retarding basins to have ephemeral wetlands constructed in their floor to treat stormwater.
16. Construction of raingardens can help water quality.
17. Water-sensitive urban design, even at the lot level can contribute to better water quality.
18. Significant reductions in hydrocarbon and heavy metal pollution can be achieved by passive filtration.
19. Structural measures for individual premises can be implemented at the planning permit stage.
20. Education and engagement programs have been demonstrated to improve the understanding of business operators and their uptake of pollution mitigation measures.
21. Water quality and litter are major concerns for users of the Merri waterways.
22. Local governments have a central role in litter management through provision of infrastructure, education and enforcement.
23. There is no systematic mapping of the locations of litter traps across the catchment or identification of the extent to which litter hotspots are being treated.
24. In addition to education programs in English it is important to communicate directly with culturally and linguistically diverse (CALD) groups.
25. Community groups play an important role in picking up litter, which could be encouraged.
26. A Litter Strategy for the waterways of the Merri Catchment is needed.
Objectives
1. Improve water quality in catchment waterways, aquifers, and wetlands, and consequently estuaries, bays and seas (from RCS-WO4).
Targets
1. Halt further decline in water quality in rural sections of the catchment, - currently poor (see Regional River Health Strategy).
2. By 2010 improve water quality of urban sections of Merri Creek from very poor to poor (see Regional River Health Strategy).
3. Improve water quality in catchment waterways so that:
- at least 80% of monitoring sites attain SEPP objectives or regional targets by 2009
- All monitoring sites attain SEPP objectives by 2030. (see RCS-WT8).
4. Maintenance of water quality in new urban development areas to levels which existed prior to development, using water sensitive urban design strategies. This includes the Implementation of higher standards and different approaches to the application of water sensitive urban design techniques and stormwater treatment so that urban development does not impact on water quality.
5. Protection and improvement of water quality in rural areas through cooperative means such as the Melbourne Water Stream Frontage Management Program.
6. Ten-fold reduction in heavy metal and other toxicant contributions to stormwater and to the Merri waterways through targeted focus on sub-catchment with small medium sized industry.
7. Reduction in organic pollutants and nutrient contributions from the Craigieburn Sewage Treatment Plant such that there is no discernable impact on Merri Creek receiving waters.
8. Ensure no impacts from any future expansion of the Wallan Sewerage Treatment Plant.
9. Focus litter control at or near source including structural, education and enforcement measures.
10. Review of Stormwater Management Plans by 2010 and continued implementation by Councils, assisted by Melbourne Water and MCMC.
11. By 2010 label every drain larger than 300mm or similar capacity entering waterways of the catchment with a sign including a unique identification number for the sign and the EPA pollution watch phone number.
Actions
See Section E page 200.
[223] Melbourne Water (2007)
[224] There are five levels of ecosystem protection in the SEPP. Modified ecosystems are the second most modified category; the least modified are the natural ecosystems. Modified ecosystems are described as being highly disturbed.
[225] toxicants includes various heavy metals. SEPP water quality objectives relate to levels in water rather than in the waterway sediments.
[226] Results of these assessment are available on the Melbourne Water website www.melbournewater.com.au/
[227] Presumably 5 years from the approval of the final document.
[228] Effective imperviousness is defined as the combined effect of the proportion of constructed impervious surfaces in the catchment, and the connectivity of these impervious surfaces to receiving water bodies.
[229] ANZECC/ ARNCANZ (2000) guidelines 80% Trigger Value
[230] Better Bays & Waterways a Water Quality Improvement Plan for Port Phillip and Western Port Draft 2008
[231] The mixing zone is the defined area around an outfall where pollution is expected.
[232] From Yarra Valley Waters submission to the Draft MCES, 1/12/2008.
[233] Faecal contamination is usually assessed using measures of E. coli, a bacterium found in the gut of warm-blooded animals. Bacteria and viruses associated with faecal contamination are primarily of concern because of the potential risk to human health. These organisms do not, of themselves, pose a risk to aquatic ecosystems although the nutrients and organic matter associated with faecal pollution do.
[234] All stormwater treatment systems wetlands, raingardens, bioretention are designed to cope with /treat a certain ARI event. Bypasses for larger storm events are built into the design of such systems.
[235] According to the Wallan Local Structure Plan Draft 2007, population in the Mitchell South Statistical Local Area, which includes Broadford as well as Wallan is expected to grow from 20310 in 2006 to 36,370 by 2030.
[236] Campbellfield Creek is a tributary of Merlynston Creek
[237] The litter trap on the Harding Street Main Drain was the focus of the study (Murfitt & Le Couteur 1997) into free advertising material mentioned above.
[238] See various MCMC annual reports
[239] VLAA(2008) Available at http://www.litter.vic.gov.au/resources/documents/People_At_Home_Kit_-_74pp_A4_Lo-Res_part_one.pdf viewed 27-1-09
Merri Creek Management Committee. 2 Lee St, East Brunswick, Victoria, Australia 3057 