Appendix E - SITA Australia

Transcription

West Australian Landfill Services
2011 SRL Annual Monitoring Report
Revision 01
Appendix E
Annual Stream Bank Assessment
West Australian Landfill Services, South Cardup Landfill
Annual Stream Bank Assessment November 2011
© GHEMS Holdings Pty Ltd.
Disclaimer
This report has been produced by GHEMS Holdings Pty Ltd
solely for the benefit of Western Australian Landfill Services.
GHEMS Holdings Pty Ltd shall resume no liability or
responsibility to any third party arising out of the use of or
reliance upon this document by any third party.
This document may not be reproduced or copied in the whole or
part without the express written consent of GHEMS Holdings Pty
Ltd and Western Australian Landfill Services.
GHEMS Holdings Pty Ltd
ABN 49 913 468 699
4 Duffy Street, Bassendean
Western Australia 6054
Ph: +61 8 9373 7100
Fax: +61 8 9373 7111
E-mail: [email protected]
Internet: www.ghems.com.au
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GHEMS Revegetation – Environmental
Contents
1. INTRODUCTION…………………………………………………………..…..........3
2. HYDROLOGY………………………………………………………………..……....4
3. STREAM BANK ASSESSMENT METHADOLOGY……………………..……...4
4. CURRENT STREAM BANK CONDITION……………………………..…………5
4.1 Vegetation Condition …………………………………………………..….……..5
4.2 Stream Bank Condition ………………………………………………..….……..6
4.3 Stream Environmental Rating ………………………………………..…….…..7
5. CURRENT IMPACTS DUE TO LANDFILL……………………………..………..8
6. IMPACTS DUE TO CURRENT LAND MANAGEMENT PRACTICES
IN ADJACENT FARMLAND……………………………………….………..……..8
7. WATER QUALITY MONITORING…………………………………………..…….8
7.1
7.2
7.3
7.4
7.5
pH levels…………………………………………………………………....…..9
Total Dissolved Solids (TDS)……………………………….……………....10
Total Suspended Solids (TSS)…………………………….…………….….11
Ammonium and Conductivity……………………………….……………...12
Leachate Spill………………………………………………………………….12
8. ACTIONS TAKEN IN RESPONSE TO PREVIOUS
RECOMMENDATIONS…………………………………………………….……….13
9. RECOMMENDATIONS FROM CURRENT ASSESSMENT……….…………..13
10. CONCLUSIONS……………………………………………………………………..14
11. STREAM BANK ASSESSMENT PHOTOS…………………………..……….…16
12. REFERENCES……………………………………………………………..…….….19
APPENDIX 1:
SOUTH CARDUP LANDFILL SITE…………………….….……20
APPENDIX 2:
FORESHORE CONDITION ASSESSMENT REPORT
(WRC, 1999)……………………………………………..…….…..22
APPENDIX 3:
ELEMENT OF THE FORESHORE CONDITION
ASSESSMENT SYSTEM (WRC, 1999)………………………...27
APPENDIX 4:
WATER QUALITY DATA……………………………….…….….34
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INTRODUCTION
South Cardup Landfill (SCL) facility is located at the base of the Darling Scarp approximately 45
kilometres south of Perth and 4.5 kilometres south of Byford along the South Western Highway.
SCL is a Class II Landfill site owned and operated by West Australian Landfill Services (WALS). It is
used as a secure containment facility for the disposal of inert, putrescible and low level commercial
and industrial wastes and employs strictly controlled landfill practices (WALS, 2004).
The purpose of this report is to outline any impacts that landfill activities may be having on the banks
of an intermittent stream (the stream) that runs through the Landfill facility. The section of the stream
west of the bottom storage dam forms the focus of this assessment (Figure 1). Rainfall data and
water quality data including pH, TDS (Total Dissolved Solids), TSS (Total Suspended Solids),
ammonium and conductivity were provided by WALS. A brief assessment on how these may affect
the stream system has been included.
GHEMS Holdings Pty Ltd. (GHEMS) has been employed by WALS to prepare an assessment of
stream condition including vegetation and bank condition, water quality analysis and identification of
items requiring action. A site visit was conducted by GHEMS consultants Matthew Blacklow and
Tyson Anderson, on 30 November 2011, and follows prior assessment of the site on 15 December
2010.
Figure 1: Survey area
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2.
HYDROLOGY
The stream runs through the valley in which the South Cardup landfill facility has been developed
and forms a part of the lower Serpentine River Catchment Area. It is a sub-catchment of the Peel –
Harvey Catchment. During normal flow periods the stream dissipates into sediments on the Swan
Coastal Plain (URS, 2000). During periods of peak flow (generally in late winter) the stream
discharges into the Cardup Brook (URS, 2000) just north of its confluence with Manjedal Brook.
From here the creek system then becomes an engineered drain which discharges into the Peel Main
Drain which in turn discharges into the Serpentine River.
The natural course of the stream through the landfill site has been altered through a series of
deviation drains which channel water around the landfill site. The deviation drain system includes a
number of dams. The stormwater drain system includes 4 dams (a surge dam, a retention dam, a
large sedimentation dam and a storage dam). The storage dam which is the last dam the stream
runs into before it leaves the landfill site forms the eastern boundary of the assessment area.
3.
STREAM BANK ASSESSMENT METHODOLOGY
A visual assessment of stream banks within the Landfill lease and the adjoining pastoral property
was undertaken (Figure 1) following methods in the Waters and Rivers Commission: Foreshore
Condition Assessment (WRC, 1999).
Both banks of the stream were traversed between the lower storage dam and the South Western
Highway. Observations were made of the stream bank condition including aquatic and fringing
vegetation condition, species diversity, stream cover, bank stability and level of sedimentation. In
addition surrounding landuse impacting on or likely to impact on the stream and fringing vegetation
were considered. By combining the stream bank assessment and assessment of surrounding
landuse an overall stream environmnetal rating was calculated with a rating of ‘Excellent’ denoting a
pristine streamline with no erosion or weed invasion to ‘Very Poor’ denoting a highly cleared and
modified streamline with significant erosion and weed invasion.
Observations of the following were also recorded: condition of riparian vegetation, bank steepness,
vegetation health, soil and level of soil cohesion, and level of protection e.g. fencing and stock
access. The soil type constituting the stream bank denotes the general soil cohesion properties and
hence the potential for erosion. Rock or stone is rated as ‘Excellent’, clay-loams are rated as ‘Good’
and sand/loose loam is rated as ‘Poor’. Notes were also made on the species of native flora present
on site and species of weeds present on site in addition to the level of invasion by these species
In addition to the Waters and Rivers Commission: Foreshore Condition Assessment (WRC, 1999),
vegetation on site was also rated using the Vegetation Condition Scale used by Keighery (1994).
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Results of the current stream condition analysis were compared with results from the last
assessment conducted 10 November 2009. Comparison highlighted any negative effects the SCL
site was having on water quality within the stream and if remedial actions were working.
4.
4.1
CURRENT STREAM BANK CONDITION
Vegetation Condition
The vegetation condition within the survey area was assessed (Nov, 2011), as B3 (Degraded) for the
bottom storage dam and enclosed WALS area west of the access road. This rating was assigned to
this assessment using the methods described in WRC, 1999 (see Appendix 3).
Natives including Melaleuca incana, Regilia ciliate, Acacia pulchella, Eucalyptus rudis and Juncas
spp are the dominant species occurring around the bottom dam area and the area west of the
access road, with many setting seed. They appear to be in good health with no signs of death,
disease or insect damage. Natural regeneration was also evident with several Acacia pulchella,
Eucalyptus rudis and Corymbia callophylla saplings noted. Typha orientalis was still present,
however its dominance compared with previous years has decreased. A thick rush bed situated
between the top and bottom storage dams acts as a filter reducing the amount of nutrients and
pollutants present within the creek system.
Weeds including Perennial Veldt Grass (Ehrharta calycina) and Kikuyu (Pennisetum clandestinum)
are the dominant understory plants throughout the bottom storage dam area and area west of the
WALS access road. This can be easily mitigated with ongoing weed control practices at correct
times. However if weed control practices are not maintained then the dominance and spread of these
species could continue and undermine further rehabilitation practices. Cotton Bush (Gomphocarpus
fruticosus), Paterson’s curse (Echium plantagnieum) and Deadly Nightshade (Solanum nigrum) are
listed as declared weeds by the department of Agriculture (DAFA, 2009). These species have been
targeted in weed removal operations and this has resulted in a minimal presence, however adjacent
land is heavily infested with these species, in particular cottonbush. Given the proximity of the
adjacent land there is a high risk of re-colonisation. Ruby Dock (Acetosa vesicaria) was also noted
but its presence was minimal. This demonstrates the ability for weeds to re-colonise areas as Ruby
Dock was mostly absent from the reporting area in the previous year. This also highlights the
importance of maintaining a stringent weed control program.
These are the main contributing factors for the B3 rating given to this area. However with sustained
recruitment understory and shrub species should, over time, act to further stabalise the banks and
reduce weed cover by competing for available light, nutrients and other limiting factors. Coupled with
continued management of the area a future rating of B2 or B1 is achievable. The overall
environmental rating however, remains unchanged and stands at 21 (MODERATE), indicating a
slight decrease from the previous year, although this is largely due to a reduction in bank stability
and increased sediment rather than vegetation condition.
In conjunction with this survey, the lower stream, running between the western boundary fence of the
WALS property lease and the South-West Highway, was also assessed.
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This area is on private land, and outside of the environmental responsibility of WALS. The
assessment found that the condition of the stream and surrounding vegetation was rated as C1
(Eroding or Erosion Prone) as per previous years. The area is dominated by weed species, with only
remnant Eucalyptus spp and localized populations of native sedges remaining. Thick, established
stands of Cotton bush were recorded along large sections and are severely impacting the
environmental values of the area, as well as providing a seed source for further infestations within
the WALS landholdings. There was much evidence of livestock activity, with associated damage to
stream bank structure, including crossing points, mud wallows and trampling of banks and
vegetation. There are very few Eucalypt seedlings/saplings, and these species are unlikely to be
able to regenerate sustainably without environmental management practices being implemented.
The overall environmental rating stands at 8 (VERY POOR), a figure that has been decreasing
gradually on a yearly basis and which appears to be getting worse. Points were lost in areas relating
to stream cover and bank stability, and can be directly related to ongoing disturbance from
unrestricted livestock access and washouts. As previously mentioned, this stream is located on
private property, and its condition cannot in any way be attributed to WALS activities or
management.
4.2
Stream Bank Condition
Stream bank slopes ranged from ‘Moderate’ (10-45°) to ‘Steep’ (45-60°) within the WALS site. The
majority of banks were of ‘Moderate’ steepness with approximately 10m of bank on the far west of
the site near the private property boundary fence being ranked as ‘Very Steep’(>60°).
Bank subsidence was noted to have increased since the last survey was undertaken, in particular
the area between ponds 1 and 2 (Appendix 2) in the area west of the access road. There are also
several new points of minor undercutting and this could further undermine bank stability in the future.
It was reported that for a period during 2010 water was cut off from entering the bottom dam as
water requirements for WALS operations increased, this may have contributed to some erosion as a
lack of permanent water can reduce soil stability. A sudden influx of water into the bottom dam can
lead to water moving at a higher velocity through the bottom dam and into the creek, removing
surface sediment at an increased rate. Debris including branches, rubbish and leaves have also
significantly reduced water flow into some areas, resulting in buildups that have led to overflows of
large volumes of water at high velocity, causing significant disturbance to fragile areas of the bank.
The level of erosion that has occurred since the last survey gives some cause for concern given that
soil cohesion remains ‘Good’ with stream banks composed of mostly gravely clay with considerable
quantities of blue metal and granite gravel. Major stream banks around Ponds 1 and 2 are now well
bedded in and further erosion in this area is unlikely. However the stream running between ponds 1
and 2 is at a higher risk of erosion. Continued monitoring to detect any further changes in bank
stability is recommended.
The fence surrounding the bottom storage area has been repaired since the last survey and has
managed to keep livestock from the WALS site, although some parts do require maintenance.
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The section of stream outside the WALS site ranges from ‘Slight’ (0-10°) to ‘Very Steep’. Areas of
undercutting noted in the previous year’s report have dramatically increased despite ‘good’ soil
cohesion with some banks now at 0. Large sections of tree roots are now exposed decreasing the
integrity of the bank. There was also evidence that livestock have access to the site given the
crossing points, hoof prints and scats situated around the stream, which in turn could further
decrease the stability of the bank. Several large mature eucalypts were also noted to have fallen
across the stream in many cases dislodging large amounts of soil as well as reducing bank stability.
It was also noted that large sections of stream running through this property have become dammed
due to a build of debris including trees, branches, leaves etc. As a result water is building up before
overflowing with an increased velocity. These problems can be mitigated with a raft of different
solutions and include removing debris to minimise damming, reducing bank steepness as well
improving bank stability however this not the responsibility of WALS and that of the land owner.
4.3
Stream Environmental Rating
The overall stream environment is currently rated ‘Moderate’ (WRC, 1999) with an environmental
rating of 21. The area has:
 Good vegetation cover, but this cover is composed of both native and exotic flora
 Localised clearing however disturbance is not recent
 Abundant shade and overhanging vegetation
 Some emergent aquatic vegetation within the stream
 Localised erosion, bank collapse and sediment heaping
 A stream environment with at least two habitat types including riffles and pools
Since the Annual Stream Bank Assessment (ASBA) provided to WALS in November 2006, the
condition of floodway and bank vegetation has remained unchanged (‘Moderate’) as the area has
localised clearing, however disturbance is not recent and has good vegetation cover, consisting of a
mixture of native and exotic flora. The condition of verge vegetation has shown slight improvement,
with mostly ‘Moderate’ conditions noted as opposed to the ‘Moderate’ to ‘Poor’ found in the ASBA
provided in November 2006. Stream cover remains unchanged (‘Good’) since 2007 with abundant
shade and overhanging vegetation and some emergent aquatic vegetation present. In the ASBA
provided in November 2006 steam cover was rated ‘Good’ to ‘Moderate’ showing that revegetation
undertaken by GHEMS in 2006, natural recruitment, fencing and weed control has improved the
stream’s condition. Bank stability has reduced from ‘good’ to ‘moderate’ with increased erosion of the
stream bank between ponds 1 & 2. If action is not taken to mitigate erosion and ensure bank
stability WALS may be in danger of losing its ‘moderate’ environmental standing. The stream is
currently supporting at least two aquatic habitats including riffles and pools.
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5.
CURRENT IMPACTS DUE TO LANDFILL OPERATION
Current impacts are minimal with full water flow returned to the creek. Likely impacts include a buildup of debris as a direct result of WALS activities.
6.
IMPACTS DUE TO CURRENT LAND MANAGEMENT PRACTICES IN
ADJACENT FARMLAND
Fences have been repaired since last year’s reporting, thus restricting access for livestock to the
WALS site, however some sections of the fence do require maintenance and if left unchecked,
livestock could return.
The presence of Gomphocarpus fruticosus (Cotton Bush) in the adjacent property is likely to be
impacting on the vegetation quality within the stream environment, as Cotton Bush seedlings
appearing in the survey area likely originate from from parent plants on the adjacent property.
7.
WATER QUALITY MONITORING
Due to the proximity of landfill operations, the water quality of the creek, including both surface water
and groundwater, is monitored to detect any changes in chemical and particulate composition. This
ensures that any impacts resulting from landfill activities are identified and can be managed to keep
water quality indicators within acceptable limits.
Monitoring of the quality of water discharging from the storage dam into the diversion stream west of
the bottom storage dam, which flows into Cardup Brook is conducted monthly by Western Australian
Landfill Service (WALS).
Data has been supplied by WALS for the period 7 January 2011 to 2 December 2011 recording the
following parameters: acidity (pH), total dissolved solids (TDS), and total suspended solids (TSS),
Ammonium and conductivity.
This data is shown in Table 1.
Monthly water quality and rainfall averages for this period are summarised in Appendix 4.
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Parameter
Range
pH
6.6-8.0
TDS (mg/L)
TSS (mg/L)
350-1300
Ammonia
Conductivity
@25 C
Discharge (SW4)
Median
Average
Range
Retention (SW1)
Median
Average
7.7
7.3-8.5
8.2
8.1
573
37
668.55
104.8
653.7
894.35
134.5
0.205
0.322
306-1400
<5-1000
<0.0050.64
8-1900
880
996.1
530-1900
1150
1283.666
Range
UD5
Median
Average
Range
UD3
Median
Average
6.2
5.9-6.4
6.3
6.3
<5-810
1.8000.071
Parameter
7.8
1.002
0.129
pH
6-6.5
TDS (mg/L)
10701160
1003.15
1114
282-964
825
724
TSS (mg/L)
<5
<5
<5
7-25
15.5
17.88
Ammonia
<0.0050.14
0.018
0.0483
0.51-2.1
0.975
0.9878
1900-2000
2000
1961
520-1400
1400
1175.556
Conductivity
@25 C
6.2
Table 1: Water Quality Monitoring Data Summary for 2011 (WALS, 2011)
7.1
pH Levels
The National Health and Medical Research Council (NHMRC) stipulates the acceptable pH range for
drinking water as being between 6.5 and 8.5 (NHMRC, 2009). Results for the assessment period of
2011 indicate that, while pH levels for surface water are neutral and fall within an acceptable range,
the underdrainage areas regularly fall outside these ranges. Of particular note is the discharge
emanating from UD5 and UD3, both of which consistently exceeded the lower pH limit. Water
discharge which exceeds the NHMRC guidelines could potentially negatively impact the water quality
in Cardup Brook.
The Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZECC &
ARMCANZ, 2000) defines trigger values for physical and chemical parameters. These values are
used to assess the point at which adverse impacts on stream environments are likely to occur.
ANZECC and ARMCANZ (2000) define upper and lower limit trigger values for pH in lowland rivers
as being between 6.5 and 8.0. As in previous years readings for underdrainage and surface water
discharge from the South Cardup site generally exceed trigger values with SW4 the only one to fall
within acceptable limits. Management and continued monitoring is recommended, especially since
SW1, UD5 & UD3 are close to acceptable pH levels.
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7.2
Total Dissolved Solids (TDS)
Total Dissolved Solids (TDS) are a measure of inorganic salts dissolved in solution (water) and can
be used as a measure of salinity. The concentration of TDS in natural waters can range widely from
<1mg/L in rainwater to 3500mg/L in seawater. The range of TDS is dependent on addition of salts
from natural weathering processes or through human activities. Total Dissolved Solids can range
from <495mg/L (fresh) to 550-1500mg/L (marginal). Rainfall is highly influential on levels of TDS and
low summer rains combined with high evaporation increases the level of TDS in solution.
On average Perth receives 854 mm of rainfall per annum. In 2011, Perth received 860.8mm of rain
slightly above average. However during 2010 only 503.8 mm of rain was recorded.
Jan Feb Mar Apr May
2012
2011
Jun
Jul
Aug
Sep Oct Nov Dec Total
5.6
30.2 0.4
5.6
0 19.4
85 171.4
161 115.2 109.2 64.2
29 75.8 860.8
Average 9.6 12.7 19.5 44.1 117.5 175.7 169.7 133.6 80.6 52.2 22.1 12.8
850
Figure 1: Cumulative Rainfall for Perth (2009-2012) and monthly rainfall data for 2011 (Water
Corporation, 2012)
Average levels of TDS for the 2010 reporting period range between 668.85mg/L – 1114.00mg/L.
Average TDS levels for SW1, SW4 and UD3 are less than that of the 2010 reporting period; however
UD5 has increased from 977.56mg/L in 2010 to 1114.00mg/L in 2011. Typically UD5 has always
10
recorded higher averages across all reporting periods. Ranges have also decreased compared with
that of the 2010 reporting period, and are more consistent with that of the 2008 & 2009 reporting
periods. However water monitoring periods (Appendix 4) indicate that there are quite sudden spikes
in TDS levels and this should be monitored closely. The reduction in overall TDS levels is likely due
to the higher rainfall experienced during with 2011 compared with that of 2010. As the the Cardup
land fill goes into remission and site activity decreases there should be a further reduction in TDS
levels. .
ANZECC & ARMCANZ (2000) measure upper and lower trigger values for TDS in millisemens
(uScm-1) and all ASBA reports measure TDS in mg/L. With no conversion possible between these
measurements it is not possible to calculate whether measurements for TDS in the current ABSA
report are within the trigger values recommended in ANZECC & ARMCANZ (2000). It is
recommended that in future WALS record all TDS measurements in uScm-1 so as comparison can
be made to ANZECC & ARMCANZ allowing my concise conclusions to be drawn.
7.3
Total Suspended Solids (TSS)
There is no guideline based on health considerations for turbidity (TSS) due to a lack of data
(NHMRC, 2004). The NHMRC (2004) have however stated that for aesthetic reasons TSS should
not exceed 5 NTU (Nephelometric Turbidity Units), and that unfiltered Australian drinking water
turbidity readings typically range from 1NTU to 65NTU. The Australian and New Zealand Guidelines
for Fresh and Marine Water Quality (ANZECC & ARMCANZ, 2000) has set a default trigger value
range of 10 NTU to 20 NTU for lowland rivers in slightly disturbed ecosystems in south-west
Australia. This guideline is highly subjective to site specific variability but is aimed at protecting a
range of aquatic ecosystems.
In Western Australia, TSS is still measured in mg/L. As there is currently no equivalent guideline for
TSS and there is no one method of conversion between mg/L and NTU, it is difficult to compare the
results of this assessment to the National guidelines for turbidity.
The State-wide River Water Quality Assessment undertaken by the Western Australian Department
of Water in 2004 (Department of Water, 2008) sets out the following guidelines for the median TSS
recording:
Low: 0 – 5mg/L
Moderate: 6 – 10mg/L
High: 11 – 25mg/L
Very High: >25mg/L
During the reporting period of 2011, average surface water TSS were 104.8 & 134.5 mg/L for SW4
and SW1 respectively, and <5 & 17.88 mg/L for UD5 and UD3. Both SW4 and SW1 have increased
substantially from the previous reporting period (54.4 & 48.86 mg/L), while UD5 & UD3 have
decreased (12.5 & 29 mg/L).
The range of TSS levels varies drastically during each sampling period and are not necessarily
consistently high, Table 1. However total rainfall was significantly higher in 2011, 860.8mm
11
compared with that of 2010, 503.8mm. Given that TSS levels typically increase during peak rainfall
months (Appendix 4) it is expected that the average TSS mg/L levels would increase given the
higher rainfall experienced during 2011. During all sampling periods UD5 consistently recorded TSS
levels less than 5mg/L, however sampling could only be conducted on six occasions (Appendix 4).
Site disturbance has not been as high in previous years and it is encouraging to see a reduction in
TSS mg/L levels from 2010 for both UD5 12.5mg/L & UD3 29 mg/L given the higher rainfall. This
places the underdrainage areas in the low and high categories set by the Department of Water,
2004.
Although the TSS levels are lower than those recorded in previous years, TSS levels are still very
high in many of the samples, especially the surface water readings.
The effect of the retention and sediment dams on water quality is positive and levels of TSS entering
Cardup Brook are likely to be higher in the absence of these structures.
It is recommended that in future WALS record all TSS measurements in NTU so as comparison can
be made to ANZECC & ARMCANZ (2000).
7.4
Ammonium and Conductivity
Ammonium and conductivity levels are below threshold levels at which point adverse impacts on
stream environments are likely (ANZECC & ARMCANZ, 2000). ANZECC define the trigger value for
ammonium in lowland rivers as being 80 µg N L-1 and define trigger values for conductivity in these
rivers
as
being
between
-1
300-1500 µScm (Table 1). No averages exceed the trigger value for ammonium, however UD5 is
the only site to exceed trigger values for conductivity with an average of 1961 µScm-1 this is an
increase from the 2010 reporting period. This is concerning given that all other sites recorded
reduced averages compared with that of 2010. Although there are reductions, spikes in conductivity
do occur over the course of the monitoring program and this requires further monitoring especially
since conductivity µScm-1 for UD5 has increased and sits above recommended trigger values.
7.5
Leachate spill
During 2010, a leachate spill occurred which resulted in approximately 100 KL being released into
the Cardup creek system. Monitoring of the surface and groundwater was conducted for each
chemical identified as a possible source of concern; nitrogen, metals, hydrocarbons and dieldrin. It is
evident during the 2011 monitoring period that there are no lasting environmental impacts from the
leachate spill and that all remediation efforts have so far worked.
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8.
ACTIONS TAKEN IN RESPONSE TO PREVIOUS RECOMMENDATIONS
As in previous years GHEMS Holdings Pty Ltd have made recommendations to WALS regarding
weed management, livestock management and revegetation works to improve the quality of the
steam and riparian zone. WALS has taken measures to fulfil these recommendations by
implementing the following actions.


9.
Water has been returned to the stream and this is critical in helping to stabilise the
stream bank as well helping to reduce erosion. It also enables the continued survival
and regeneration of fringing vegetation.
The boundary fence has been repaired and has halted livestock from entering the
WALS site, however regular upkeep and maintenance is required to ensure livestock
do not gain access in the future.
RECOMMENDATIONS FROM CURRENT ASSESSMENT
The following actions are recommended to increase water quality and the condition of vegetation in
and around the stream draining from the WALS site into Cardup Brook
Recommendations:
 Continued maintenance and repairs of boundary fencing. If left unchecked livestock may
return and could easily undermine the progress made in previous years in regard to
vegetation cover and natural regeneration. It is also critical livestock do not return to the area
given the fragile state of the steam bank.
 Remove debris and rubbish from stream and ponds on the WALS site to reduce water build
ups and overflow, leading to further erosion damage.
 Although not the responsibility of WALS, contact should be made with the adjacent land
owner who shares Cardup creek, in regard to removal of declared weeds, debris in creek as
well as restricting livestock access to the creek.
 Further revegetation should be undertaken along the steam bank east of the access road to
minimise further erosion and undercutting damage. Revegetation should focus on increasing
the percentage of Baumea articulata as this acts to stabilise the stream banks, reduces water
flow, assists in sediment deposition, nutrient and pollutant stripping.
Previous recommendations:


Hydrologists evaluate the bottom storage dam with the aim of increasing the dam’s size so it
has the capacity to hold and slow a large volume of water. This action will give greater time
for sedimentation thus reducing TSS and as the dam dries through summer sediment can be
removed thus also removing any salt crust and potentially reducing TSS when the dam fills in
winter.
Weed control be expanded to target not just Declared Weed Species (DAFWA 2008) but to
target all weed species on the site. Weed control combined with small scale revegetation
works will see considerable increases in the ecological services this stream provides and a
reduction in the impact the WALS South Cardup site has on water quality downstream.
Weed control will also see the Stream Environmental Rating increase (WRC, 1999).
13


Readings for Total Suspended Solids (TSS) be taken in both mg/L and NTU (Nephelometric
Turbidity Units) so accurate comparisons with National Guidelines and ANZECC &
ARMCANZ (2000) can be made.
Readings for Ammonium and TDS/conductivity be recorded in N L-1 and uScm-1, respectively
so as comparison can be made with guidelines prescribed in ANZECC & ARMCANZ (2000).
Actions to continue:
 Maintenance of weed control for Declared Weed Species (DAFWA 2009).
 Maintenance of fencing to exclude livestock.
 Maintenance of mobile rubbish collection.
 Maintenance of regular water quality monitoring including assessment of Total Dissolved
Solids (TSS) discharging into the stream from the storage dam.
10.
Conclusions
This assessment has rated the foreshore condition of WALS site as B3 ‘degraded’- understory weed
dominated, with natives occupying most of the canopy. Regeneration is occurring and this is crucial
in reducing the percentage of weeds while increasing the foreshore condition rating of the WALS
site. Revegetation works undertaken by GHEMS Holdings Pty Ltd has continued to improve the
condition of the area west of the access road, however erosion and undercutting is present along
some sections of the stream bank and appears to have become worse than in previous years, thus
revegetation focusing on Baumea articulata should be undertaken to stabilise the stream bank
(section 8).
Unfortunately the adjacent land is rated as C1 ‘Eroding or Erosion Prone’. Although not the
responsibility of WALS, overall improvement of foreshore condition on the WALS site cannot happen
without mitigation of environmental factors on both sides.
The overall Stream Environmental Rating remains at ‘Moderate’ (WRC 1
). On the whole the site
appears to be improving, however points were lost given the erosion and undercutting that is
prevalent around the stream bank west of the access road. The rating can be improved by mitigating
erosion and undercutting problem. Continued weed control and increasing fringing vegetation will
also help improve the environmental rating. If efforts are not made to remediate both erosion and
weed problems, the overall environmental rating may be downgraded to poor during the following
reporting period.
Several weed species were recorded during the current survey (section 4.1), with two of these
species (Cotton Bush and Patterson’s Curse) being noted as declared weed species (DAFWA,
2008). Weed invasion, most importantly by Cotton Bush, has potential to further impact on the
stream. Although WALS is attempting to manage this issue, the infestations on the adjacent property
will continue to affect the weed management within the landfill lease and should be addressed by the
landholder. Several species such as ruby dock (Rumex vesicarius) that were not present during the
2010 reporting period were identified during this reporting period and although only several plants
were recorded, it highlights the importance of maintaining a more thorough weed control program
and the difficulties associated with high weed infestations on adjacent properties.
14
The fence has been maintained and appears successful in restricting livestock access to date.
However some sections of the fence appear to be in need of further maintenance leaving the
opportunity for livestock to gain access in the future if repairs are not undertaken.
The issue of mobile rubbish will continue for the life of the facility, with the potential for pollution
further downstream potentially blocking culverts and interfering with stream flow. Staff at WALS have
been taking measures to reduce mobile rubbish on site and on the adjacent property through regular
rubbish collection and removal. This has been on the most part successful and it is critical to
maintain a regular rubbish removal program.
Erosion in some sections of the stream, particularly between ponds 1 & 2 has increased slightly and
this could become a concern in the future. The creek was dry for a period during 2010 when WALS
water requirements increased, but this in turn destabilised the steam bank. Given the higher rainfall
in 2011 compared with 2010, much of the surface sediment has potentially been removed. Rubbish
and debris build up in the stream can cause some sections to become dammed, thus increasing
water velocity with overflow occurrences, which in turn remove surface sediment and de-stabilise the
stream bank.
Nonetheless, current management practices have stabilised the stream banks and improved the
quality of waters in the stream over the recording period. Recommendations outlined in section 10
should be implemented to further increase the stream’s health reduce TSS/TDS and to keep water
parameters such as pH, Ammonium and conductivity within limits that will not adversely affect the
streams biota.
15
11.
STREAM BANK ASSESSMENT PHOTOS
Photo 1: Rubbish in the top storage dam eventually makes its way down the creek and can block
culverts. If left unchecked it can contribute to damming of smaller sections of the creek.
Photo 2: Erosion of stream bank between ponds 1 and 2 west of the access road. This section
continues for several meters.
16
Photo 3: Erosion and undercutting of surface sediments around the bottom storage dam. If left
unchecked this could further increase.
Photo 4: Fallen trees across the creek enable debris and rubbish to build up, damming water and
leading to overflows of high velocity water which in turn can lead to erosion of surface sediments and
thus de-stabilisation of the stream bank.
17
Photo 5: Although much of the boundary fence has been repaired, fallen branches have damaged
some sections of the fence. If left unchecked, livestock could return to the area.
Photo 6: Eucalypt sapling located around bottom storage dam. Numerous saplings were noted
during this assessment and this provides encouraging sings for the area.
18
12.
References
ANZECC & ARMCANZ. (2000). National Water Quality Management Strategy: An Introduction to
Australian and New Zealand Guidelines for Fresh and Marine Water Quality. Canberra,
ANZECC. Retrieved 12 November 2009 from:
http://www.mincos.gov.au/publications/australian_and_new_zealand_guidelines_
for_freh_and_marine_water_quality
DAFWA. (2008). Declared plants list, Agriculture and Related Resources Act, 1976. Agriculture
Protection Board: South Perth, WA. Retrieved 12 November 2009 from:
http://www.agric.wa.gov.au/PC_93088.html?s=1001,Topic=PC_93079
Department of Water, Western Australia. (2008). Statewide river water quality
Assessment. Retrieved 25 February 2008 from:
http://apostle.environment.wa.gov.au/idelve/srwqa/metadata_statements/srwqa.html
Keighery, B.J. (1994). Bushland Plant Survey: A Guide to Plant Community Survey for the
Community. Wildflower Society of WA (Inc.) Nedlands, Western Australia.
National Health and Medical Research Council. (2004). National water quality
management strategy: Australian Drinking Water Guidelines 6. Retrieved 12 November 2009
from:
http://www.nhmrc.gov.au/_files_nhmrc/file/publications/synopses/adwg_11_06.pdf
URS. (2000). Annual assessment of stormwater discharge from the southern
landfill, South Cardup, to the Serpentine River.
Water Corporation. (2009). Rainfall in Western Australia: Rainfall in Perth (cumulative). Retrieved 8
January 2012 from:
http://www.watercorporation.com.au/R/rainfall.cfm
West Australian Landfill Services (2008). Annual water sampling results for retention, sediment and
bottom storage dams. (pers com Ron Boucher, February 2008)
WRC. (1999). Planning and Management: Foreshore condition assessment in
farming areas of south-west Western Australia. Water and Rivers Commission River
Restoration Report No. RR3
19
APPENDIX 1:
SOUTH CARDUP LANDFILL SITE
20
21
APPENDIX 2:
FORESHORE CONDITION ASSESSMENT REPORT (WRC, 1999)
22
23
24
25
26
APPENDIX 3:
ELEMENT OF FORESHORE CONDITION ASSESSMENT SYSTEM (WRC, 1999)
27
3. Elements of the foreshore condition
assessment system
The foreshore condition assessment has been developed
from observations of river system degradation
throughout south-west Australia. The system follows the
general process of remnant bush degradation, with the
added complication of erosion as stream banks become
exposed.
The system has been designed to allow for a varied level
of assessment. It consists of a number of stages or
grades, A, B, C and D, beginning at pristine and running
through to completely degraded. To perform more
detailed surveys each grade has three sub-levels that are
easy to recognise (section 3.2).
3.1 Foreshore condition - basic
assessment
The basic survey is used when assessing long river
sections or for a basic survey at paddock level. In the
basic survey, you grade the foreshore into one of four
categories, A, B, C and D. Just tick the appropriate box
on the survey form.
These grades are simple to
recognise and are illustrated in Figure 2 and on the
paddock scale survey form (section 4).
A grade is where the foreshore has healthy native bush,
similar to that which you would see in most
nature reserves, state forests and national parks.
B grade is where the bush along the stream has been
invaded by weeds, mainly grasses, and looks
like typical roadside bush. For example, in
winter, soft light green leaved grasses are
usually seen, along with flatweeds and maybe
more substantial weeds such as Watsonia and
bridal creeper.
In summer or autumn, dry,
yellowing dead grasses or their remnant seed
heads are seen amongst the bush.
C grade is where the foreshore supports only trees over
weeds or pasture, or just plain pasture, and
bank erosion and subsidence may be occurring,
but only in a few spots.
D grade is where the stream is little more than an
eroding ditch or a weed infested drain. Here,
think of the typical drains you have seen, either
just after having been cleaned out with a
backhoe or in need of a clean out.
If the condition of the foreshore varies, tick the box on
the survey form that you think best represents the
general overall condition.
3.2 Detailed assessment of foreshor e
condition
If you are interested, and have the confidence, you
can assess foreshore in more detail. Each grade has
three sub-categories. They are reasonably simple to
recognise.
A1. Pristine
The river embankments and floodway are entirely
vegetated with native species, and there is no evidence
of human presence or livestock damage.
A2. Near pristine
Native vegetation dominates. Some introduced weeds
may be present in the understorey, but not to the extent
that they displace native species. Otherwise there is no
evidence of human impact. (A river valley in this
condition is as good as will be found today)
A3. Slightly disturbed
Native vegetation dominates, but there are some areas of
human disturbance where soil may be exposed and
weeds are relatively dense (such as along tracks). The
native vegetation would quickly recolonise the disturbed
areas if human activity declined.
B1. Degraded - weed infested
Weeds have become a significant component of the
understorey vegetation. Although native species are
dominant, a few have been replaced by weeds.
28
29
B2. Degraded - heavily weed infested
In the understorey, weeds are about as abundant as
native species. The regeneration of some tree and large
shrub species may have declined.
B3. Degraded - weed dominated
Weeds dominate the understorey, but many native
species remain. Some trees and large shrub species may
have declined or disappeared altogether.
C1. Erosion prone
Trees remain, and possibly some large shrubs or tree
grasses, but the understorey consists entirely of weeds,
mainly annual grasses. The trees are generally resilient
or long lived species but there is little or no evidence of
regeneration. The shallow-rooted weedy understorey
provides no support to the soil, and only a small increase
in physical disturbance will expose the soil and make the
river embankments and floodway vulnerable to erosion.
become a simple drain, similar or identical to a typical
major urban drain.
Sometimes when assessing the condition of a foreshore
you may think it is too variable to tick any one box and
you may wish to express the full range of condition.
This can be done. For example, you may think that the
condition ranges between A3 and B2. If so, simply tick
both boxes. On the other hand, you may think that while
it is mainly B1, it ranges between A3 and B2. In this
case tick A3 and B2, and tick B1 twice. Similarly, if you
think it ranges between A3 and B2, but is mostly B2, tick
A3 once and B2 twice.
The survey forms are also designed to allow for the
collection of other information relating to soils, bank
stability and environmental health that you may find
useful when planning management works. The
collection of this information is optional and is discussed
further is Section 4.
3.3 Fencing status
C2. Soil exposed
Older trees remain, but the ground is virtually bare.
Annual grasses and other weeds have been removed by
livestock trampling or grazing, or through over use by
humans. Low-level soil erosion has begun, by the action
of either wind or water.
This will provide information on whether the stream is
fenced off or not and whether stock have access to the
land.
C3. Eroded
Stock access - tick yes if it appears that stock have had
access to the river/creek recently, even if the streamline
is fenced off.
Soil is washed away from between tree roots, trees are
being undermined and unsupported embankments are
subsiding into the river valley.
Fenced off - tick yes only if the the fence is in good
order and is actually functioning as a fence.
Crossing point - tick yes if there is a livestock or vehicle
crossing point across the stream.
D1. Ditch - eroding
There is not enough fringing vegetation to control
erosion Some trees and shrubs remain and act to retard
erosion in certain spots, but are doomed to be
undermined eventually.
D2. Ditch - freely eroding
No significant fringing vegetation remains and erosion is
completely out of control. Undermined and subsided
embankments are common, and large sediment plumes
are visible along the river channel.
D3. Drain - weed dominated
The highly eroded river valley has been fenced off,
preventing control of weeds by stock. Perennial (longlived) weeds have become established. The river has
3.4 Additional information
As well as general stream condition there are other
factors that you can assess which will provide valuable
information to assist with planning your management
options. These factors will help you to prioritise works
and to identify areas that may be prone to degradation.
3.4.1 Bank steepness
Steep banks are more prone to erosion and collapse than
more moderately sloped ones.
Combined with soil
cohesion information, this will highlight points of high
erosion hazards. Tick the box which best represents the
foreshore being surveyed.
30
3.4.2 General Soil Cohesion
• Verge vegetation
The degree of cohesiveness of the stream embankment
determines how vulnerable it is to erosion and
subsidence once the supporting vegetation has been lost.
Rocky embankments are extremely cohesive and the
erosion of surface sediment is limited. Clayey soils are
reasonably cohesive and only erode slowly, although
loose surface sediment is quickly lost. Non-cohesive
embankments of sand, loam or dispersive clays are the
most prone to erosion and collapse. Tick the box which
best represents the foreshore being surveyed.
• Stream cover
3.4.3 Major Erosion/siltation
Any point of erosion that produces more than a trailer
load worth of sediment can be considered ‘major’.
Erosion types include simple cutting into the stream
bank, undercutting of stream banks, firebreak or track
washouts, and subsidence. Also indicate if there are
large heaps of sediment, usually seen as white sand. Use
the comments to give additional information such as the
extent of the erosion or whether sediment is filling a
river pool. This information will be used to identify
“black spot” areas. Tick the appropriate boxes.
3.4.4 Vegetation health
Use this section to give a general description of the
health and vigour of the vegetation. This information is
needed to identify sections of foreshore that may
become unsupported by trees in the near future. Be sure
to note the presence or absence of regenerating trees.
The mature trees may be dead or sick looking, but if
young ones are present, they may replace the old ones.
Alternatively, adult trees may be healthy but no
regeneration is occurring. Tick the appropriate boxes.
3.5 Stream health assessment - living
streams survey
The living streams survey provides an indication of
stream health based on an assessment of the quality and
diversity of habitats. The following factors are used as
assessment parameters to help identify the health of the
habitat around the stream you are monitoring (see
sections below for an explanation of these):
• Bank stability and erosion
• Habitat diversity
• Surrounding land use
Plants provide habitat for birds, frogs, possums, and
many other organisms which live in and around streams.
The completeness of this zone is important for the
existence and health of all types of creatures ranging
from mosquito larvae through to large birds and
mammals. Leaf litter from overhanging trees, and fallen
branches provide a food and shelter for fish, crayfish and
other aquatic life.
Shade provided by overhanging
vegetation influences stream temperatures and light.
Rivers and streams which are dominate by introduced
plants (exotics), such as willow trees, cannot supply a
year round shelter and food supply which is so important
for our aquatic life.
Each of the assessment parameters is ranked from
excellent through to very poor. A numerical score has
also been given to each ranking and the score system
has been calculated to give more weighting to conditions
which are more important to stream health, such as
shade and the presence of areas of permanent water,
which are very important to aquatic life in a region
characterised by long hot dry summers. Add up the total
value of all the boxes you have ticked on your record
sheet under stream environmental health rating. This
will give you a total score, which you can evaluate
against the table below to give you an overall rating of
stream health.
Score
Rating
40-55
Excellent
30-39
Good
20-29
Moderate
10-19
Poor
0-9
Very poor
• Floodway bank and vegetation
31
3.5.1 Floodway and bank vegetation
This vegetation grows in the floodway (Fig. 1) or on the
banks and is the major natural source of nutrients and
carbon for the stream ecosystem. The canopy is the tree
cover that overhangs the stream. Plant roots stabilise the
floodway and banks against erosion and subsidence.
Stems and foliage dissipate the energy of floodwaters,
reducing erosion and promoting sedimentation.
3.5.2 Verge vegetation
The stream verge extends from the top of the
embankment to a paddock fence, backyard fence or road,
and is usually about 10-50 m wide. Sometimes the verge
is part of streamside parkland. Verge vegetation provides
habitat next to water, increases the value of the riparian
zone as an ecological corridor and stabilises the stream
banks by anchoring them with tree roots to adjacent land.
3.5.3 Stream cover
Fish and other aquatic organisms require snags, leaf
litter and rocks to shelter from predators and fast flowing
water, to reproduce, establish territories, and for
navigation. Aquatic plants are also very important for
fish and other creatures in the stream. They have a direct
effect on the available oxygen in the water, which in turn
can affect the type of fish and other animals found.
Protruding snags and rocks provide roosting and
preening sites for birds and help to oxygenate water in
fast flowing sections.
Overhanging and emergent
vegetation provides shade to which many aquatic
animals retreat during the hot days of summer and
autumn. Insects blown from flowers and leaves are a
very important source of food for fish and other animals.
3.5.4 Bank stability and erosion
Banks sometimes naturally erode on bends (meanders).
However, when vegetation is cleared for agricultural
activities and urban development, the stream banks can
become unstable, resulting in extensive erosion along
the floodway and the build-up of sediment that is then
slowly washed downstream. Erosion and bank collapse
can also be caused by increased runoff from impervious
surfaces (e.g. car parks), from pipes and drains, and by
straightening or channelling the stream.
3.5.5 Habitat diversity: cascades, runs
riffles, pools and meanders.
Different habitat types in streams include cascades,
rapids, riffles, waterfalls (which are quite rare), runs,
meanders, pools and floodplains. Stream sections that
have a range of habitat types can support a greater
variety of species.
Rapids occur where rocks and snags protrude through
rapidly flowing water. Areas where water flows quickly
over stones and rocks, or between tree stems, are known
as riffles. Areas where the water surface is essentially
flat, are known as runs. Rapids and riffles aerate water
and provide habitat for invertebrates. It is common for
the stream floodway, including rapids and riffles, to be
heavily vegetated.
The vegetated floodways are usually broken by deep
pools which provide habitat for fish, turtles, marron and
other animals. Pools are often the only parts of streams
to retain water over summer, providing an essential
drought refuge.
Long broad sections of vegetated or clear floodway are
typical of the lower reaches of our larger south-west
rivers. They provide different types of habitats because
the cutting action of water at bends creates deeper areas
and variable water speed. Seasonal floodwaters adjacent
to the stream may provide important breeding and
feeding habitat for aquatic life.
3.5.6 Surrounding land use
The surrounding land use activities will contribute
greatly to the ecological value of the stream. An area of
national park or remnant bush contribute to, and benefit
from, a wider biological diversity than can be found in
either the stream or bushland alone. A stream in an
agricultural setting will have elevated sediment and
nutrient levels, while a stream in an urban or industrial
area will be more vulnerable to weed invasion and
pollution. Native animals living in urban and semi-rural
areas benefit from a stream environment or from the
remnant bush along its flanks.
32
33
APPENDIX 4:
WATER QUALITY DATA
34
35
36
37
38
39

Appendix E - SITA Australia

Transcription

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