Page 1 FINAL Version Rosebery WWTP and Discharge DPEMP Ph: +61 3 62 378 325 www.taswater.com.au TasWater Rosebery Wastewater Treatment Plant and Discharge Development Proposal & Environmental Management Plan (DPEMP) 12 th June 2014 TRIM Ref: RY101-SE01-J03-042 C14/12640 TasWater
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Table Index ................................................................................................................................................... 6
Figure Index .................................................................................................................................................. 7
2.1. Site Plan .......................................................................................................................................... 16
2.1.1. Services to Site ........................................................................................................................... 18
2.4. Proposed Treatment Process ......................................................................................................... 23
2.5. Construction ................................................................................................................................... 27
3.2.5. Surface Water ............................................................................................................................. 57
3.2.5.1. Stitt River ................................................................................................................................ 58
3.2.5.2. Lake Pieman ........................................................................................................................... 58
3.2.6. Conservation Reserves and Wilderness Areas ........................................................................... 59
4.15.2. Safety Data Sheets (SDS) ............................................................................................................ 86
4.15.3. Safety, Environmental and Quality Audits and Surveillance ...................................................... 87
4.15.4. Risk Assessment or Job Safety and Environment Analysis (JSEA) .............................................. 88
4.15.5. Workplace Safety and Regulations ............................................................................................. 88
4.16. Fire Risk ...................................................................................................................................... 89
Figure 1 – Site Plan ..................................................................................................................................... 16
Figure 2 - General WWTP Arrangements ................................................................................................... 25
Figure 3 – Proposed WWTP Plan ................................................................................................................ 26
Figure 4– LIDAR Contour Plan of Site ......................................................................................................... 50
Figure 5 – GeoTon Site Plan - Proposed WWTP and Outfall Pipeline (Re: Fig 2 in GeoTon report) .......... 53
Figure 6 –Waterways Downstream of WWTP and Outfall Pipeline .......................................................... 57
Table 5 – AMT Tasmania WWTP Effluent Quality Limits into Fresh Water
Parameter Units Median (50%ile) 90%ile Maximum
BOD mg/L 5 10 15
Non-Filterable Residue mg/L 10 15 20
Thermotolerant Coliforms cfu/ 100mL n/a n/a 200
Oil and Grease mg/L 2 5 10
Total Nitrogen mg N/ L 7 10 15
Ammonia mg N/L 1 2 5
Total Phosphorus mgP/L 0.5 1 3
pH n/a n/a 6.5 – 8.5
Ref: Table 1 “Emission Limit Guidelines for Sewage Treatment Plants that Discharge Pollutants into Fresh and Marine
Waters”, DPIWE June 2001
Due to the sensitivity of the proposed receiving water and the fact that chlorination is not considered to
be AMT for WWTP discharges to inland waters, chlorination is not proposed as part of any disinfection
treatment process.
2.4. Proposed Treatment Process
In April 2013, TasWater commenced an Expression of Interest (EOI) process to select a suitable WWTP
for Rosebery. All potential suppliers were advised that the WWTP and associated technology MUST
consider the following site specific issues:
The high rainfall and Rosebery’s isolated location on the West Coast of Tasmania.
The plant’s ability to accommodate the operational conditions from the existing Rosebery sewage network ie hydraulics, operational, environmental and construction constraints.
Adoption of design process to accommodate both low and high inflows due to extreme rainfall infiltration into the existing sewage network, noting that Rosebery has an average yearly rainfall of approximately 2,000mm.
Treatment of contaminants identified in the influent that are expected to be of key concern for discharge to the receiving environment including:
a) Nutrients b) Conductivity c) NFR
The EOI process highlighted 2 WWTP preferred suppliers that have been assessed by an independent
third party who also prepared a detailed design and construct tender (D&C) documents. The successful
tender for the preferred supplier has been assessed against a in- depth evaluation process and has been
awarded to Factor UTB in March 2014.
The treatment plant process summary is detailed in Table 6, and a general WWTP arrangement and plan diagram is detailed in Figure 2 and Figure 3. A detailed process flow diagram is detailed in Appendix U1.
Detailed below are a number of site specific issues that will be impacted by this development. These all
relate to Commonwealth, State and Local requirements that must be met to satisfy all parties that this
project can proceed.
3.1. Planning Aspects
Rosebery is located within the West Coast Council (WCC) municipal area. Therefore the West Coast
Planning Scheme 1999 applies to this project. This DPEMP is intended to help gain approval to construct
all works proposed on site including the WWTP, TasWater amenities building, discharge pipeline and
access road.
The proposed site area is located off Chester Avenue and is zoned “Rural Resource”. The intent of the
Rural Resources Zone in the scheme is to:
26.1.1.1 To provide for the sustainable use or development of resources for agriculture, aquaculture, forestry, mining and other primary industries, including opportunities for resource processing. 26.1.1.2 To provide for other use or development that does not constrain or conflict with resource development uses.
Sub-section 4.1 Planning Terms and Definitions of the WCC Planning Scheme classes a “Utilities” use a “Permitted” use in the zone if it is minor. The development proposal is not considered to be minor and therefore does not comply with this part of the Planning Scheme provision. Sub-section 8.2 of the Scheme, Table 8.2 Use Classes defines the use of “Utilities” as land for utilities and infrastructure including, amongst other matters, the collecting treating, or disposing of storm or floodwater, sewage, or sullage. However, being as the “Utilities” use is the subject of the DPEMP, the Scheme provides for the use to be treated as a “Discretionary “use class. Within the scheme, Sections 26.3 to 26.4 sets out the planning scheme standards applicable to use of development in the Rural Resource zone. The following Scheme Codes are also relevant to the proposed development:
E1 - Bush Fire Prone Areas – Hazardous Uses, E3 - Clearing and Conversion of Vegetation, E6 - Hazard Management, E9 - Traffic Generating Use and Parking Code, E10 - Water and Waterways.
Specific relevant issues that are applicable and relevant to this project are summarised in the table below and include the location within the DPEMP where each issue is addressed in detail:
Reference Title Objective or/and Acceptable Solution
and/or Performance Criteria
DPEMP Reference Comments
26.3
26.3.1
Requirement for discretionary non-residential use to locate on rural resource land
Objective
Other than for residential use, discretionary permit use of rural resource land is to minimise –
(a) unnecessary loss of air, land and water resources of significance for sustainable primary industry and other permitted use, including for agricultural use dependent on the soil as a growth medium; and
(b) unreasonable conflict or interference to existing or potential primary industry use, including agricultural use, by other land use
Section 4 – Potential Environmental Effects and their Management
The land is not currently used for agricultural purposes and the land and surrounding land are on Crown Land with a mining lease (Tender Id 11184, Reference 28M/1993) until 2024 granted to MMG Australia Ltd for Category 1 - Metallic Minerals, Atomic Substances and Category 3 - Construction Minerals. The area immediately to the west between the WWTP site and Pieman Lake is part of the Mt Read Strategic Prospectivity Zone. Thus, there is no unreasonable interference or constraint or unnecessary loss of air, land and water resources of significance for sustainable primary industry. Nor does the development represent any unreasonable conflict to existing or potential primary industry use, including agriculture use, by other land use.
26.3.2 Required Residential Use N/a Being as this sub-section of the Planning Scheme deals with residential use and the proposal on the subject land is not concerned with residential use this part of the Planning Scheme
26.3.3 Residential Use N/a Being as this sub-section of the Planning Scheme deals with residential use and the proposal on the subject land is not concerned with residential use this part of the Planning Scheme is not applicable.
26.4
26.4.1
Development Standards
Suitability of a site or lot a plan of subdivision for use or development
Objective
The minimum properties of a site and of each lot on a plan of subdivision are to –
(a) provide a suitable development area for the intended use;
(b) provide access from a road; and
(c) make adequate provision for a water supply for the drainage disposal of sewerage and stormwater
Table 9.1 Road access and setback
Figure 1 – Site Plan and Figure 8 – Proposed BPZ and FMBZ around WWTP
The proposed WWTP site was identified as the preferred location based on social, engineering and environmental criteria which determined that the site:
• Is set back from existing Rosebery residential areas, and downstream of the section of Stitt River that flows through the township,
• Has good vehicular access off existing road networks, and an existing access track (which will be upgraded),
• Already has an existing TasWater sewage treatment asset which defined existing sewage treatment processing had already been undertaken at the site(an 18 metre diameter, 1.4 metre high 0.3 ML open steel tank) with scope to expand the site to the west to accommodate
(ii) clear of any applicable setback from a frontage, side or rear boundary;
(iii) clear of any applicable setback from a zone boundary;
the site (an 18 metre diameter,
1.4 metre high 0.3 ML open steel
tank) with scope to expand the
site to the west to accommodate
the new plant.
In addition to the WWTP
components (switchboard, inlet
works, treatment process,
disinfection and balance tank),
the site will also include an
amenities building will be
situated adjacent to the new
wastewater treatment tank
compound. The building
measures 8m x 11.1m with an
outside veranda extending the
building with a depth of 5m on
the eastern side and 3.5m on the
southern side. The building
measures 197.05m in area which
complies with the Scheme
requirement on size. Refer to
drawings contained in Appendix
A.
The development includes 5 car
parking spaces.
The Scheme’s setback requirements are complied with the purpose of protecting the environmental and visual qualities of landscapes through ensuring that buildings,
(v) clear of any registered right of way benefiting other land;
(vi) clear of any restriction imposed by a utility; water supply and for the drainage and disposal of sewage and stormwater;
(vii) not including an access strip;
(viii) accessible from a frontage or access strip
structures and other works on steep slopes are located and constructed so as to minimise impact.
The 20m setback requirement to the frontage of the lot is exceeded by 127.38m.
The 10m side setback requirement is exceeded by 100m on the eastern side and 94.68 on the western side.
The 10m rear setback requirement is exceeded by 55.3m.
There are no easements to be clear of.
There are no right of ways to be clear of.
The treatment of wastewater treatment plant is clear of any restriction imposed by a utility.
N/a
The site is accessible by a hard standing gravel access track which will be widened from 5 to 6m to accommodate two vehicles passing along an access strip from Chester Avenue to the WWTP. The road frontage measures 29.22m.
A site or each lot on a plan of subdivision must be of sufficient area for the intended use or development without likely constraint or interference for –
(a) erection of a building if required by the intended use;
(b) access to the site;
(c) use or development of adjacent land;
(d) a utility; and
(e) any easement or lawful entitlement for access to other land
Being as the proposal complies with the Acceptable Solution 1 the Performance Criteria 1 becomes redundant.
Acceptable Solution 2
A site or each lot on a plan of subdivision must have –
(a) a frontage upon a road of not less than 6.0m;
(b) access provided by a rightof-way to a road over land not required as the sole or principle means of access to any other land of a width not less than 6.0m; or
(c) an access strip to a road not required as the sole or principle means of access to any other land of a width not less than 6.0m; and
(d) vehicular access between the carriageway of a road and the frontage or
Figure 1 – Site Plan
Appendix A – Site Plans
The road frontage measures 29.22m, thus complying with proscribed Scheme provision.
A right-of –way is not required for access purposes.
The access strip from Chester Avenue stretches a distance of 147.38m to the WWTP footprint, bordering on both sides by Crown Land.
access strip provided in accordance with the Local Government (Highways) Act 1982 or the Roads and Jetties Act 1935
carriageway of a road and the frontage or access strip is provided in accordance with the subject Act.
Performance Criteria 2
It must be unnecessary to require
(a) a frontage; or
(b) an access strip; and
(c) access between the carriageway of a road and the frontage or access strip
Being as the proposal complies with the Acceptable Solution 2 the Performance Criteria 2 becomes redundant.
Acceptable Solution 3
Unless for agricultural use dependent on the soil as a growth medium, a site or each lot on a plan of subdivision must have a water supply –
(a) provided in accordance with the Water and Sewerage Industry Act 2009; or
(b) from a rechargeable drinking water system R 3 1 with a storage capacity of not less than 10,000 litres if–
(i) there is not a reticulated water supply; and
(ii) development is for –
a. a single dwelling; or
b. a use with an equivalent population of not more than 10 people per
Section 2.2.2 – Services to the Site
An underground water supply pipeline and overhead power supply will be extended into the site off Chester Avenue. The service will be installed parallel and adjacent to the access road into the site. Excavation and reinstatement is required to install the underground water supply pipe (trench width 600mm maximum), with excavation for 3 or 4 private power poles.
(iii) the site has capacity for on-site disposal of domestic waste water in accordance with AS/NZS 1547: 2000 on –site domestic-wastewater management clear of any defined building area or access strip.
Not applicable as the purpose of the development is to provide a single point of collection, treatment and disposal of sewage for Rosebery.
Performance Criteria 3
(a) There must be a water supply available for the site or for each lot on
a plan of subdivision with an adequate level of reliability, quality, and quantity to service the anticipated use of the site or the intended use of each lot on a plan of subdivision; or
(b) It must be unnecessary to require a water supply
Being as the proposal complies with the Acceptable Solution 3 the Performance Criteria 3 becomes redundant.
Acceptable Solutions 4
Unless for agricultural use dependent on the soil as a growth medium, a site or each lot on a plan of subdivision must drain sewage and trade waste –
(a) to a sewerage system provided in accordance with the Water and Sewerage Industry Act 2009; or
(b) by onsite disposal if –
(i) sewage or trade waste cannot be drained to a reticulated sewer system; and
Section 2.1.1 – Services to Site
The plant’s purpose is to provide a single point of collection, treatment and disposal of sewage for Rosebery.
There are currently no trade waste agreements within Rosebery, and no major industries are connected to the
b. provides for an equivalent population of not more than 10 people per day; or
(iii) the site has capacity for onsite disposal of domestic waste water in accordance with AS/NZS 1547:2000 onsite domesticwastewater management clear of any defined building area or access strip
sewerage system. Extensive influent water quality testing as detailed in the report, no significant trade waste issues have been identified or are expected within the Rosebery catchment.
n/a
Performance Criteria 4
a) A site or each lot on a plan of subdivision must drain and dispose of sewage and trade waste –
(i) in accordance with any prescribed emission limits for discharge of waste waters
(ii) in accordance with any limit advised by the Tasmanian Environmental Protection Agency;
(iii) without likely adverse impact for the health or amenity of the land and adjacent land;
(iv) without compromise to water quality objectives for surface or ground water established under the State Policy on Water Quality Management 1997; and
(v) with appropriate safeguards to minimise contamination if the use or
Being as the proposal complies with the Acceptable Solution 4 the Performance Criteria 4 becomes redundant.
a. indirectly cause the contamination of surface or ground water; or
b. involve an activity or process which requires the use, production, conveyance or storage of significant quantities of sewage or trade waste that may cause harm to surface or ground water if released through accident, malfunction, or spillage; or
(b) It must be unnecessary to require the drainage and disposal of sewage or trade waste
Acceptable Solutions 5
Unless for agricultural use dependent on the soil as a growth medium, a site or each lot on a plan of subdivision must drain stormwater –
(a) to a stormwater system provided in accordance with the Drains Act 1954 ; or
(b) if storm water cannot be drained to a stormwater system –
(i) for discharge to a natural drainage line, water body, or watercourse; or
(ii) for disposal within the site if –
a. the site has an area of not less than 5000m2;
Appendix A – Site Plans
Stormwater is to be drained by a direct pipe directed to existing open drain besides roadway. Ultimately the gravitational drain has an outfall into the Stitt River some 250m distance. This method complies with the acceptable solution.
b. the disposal area is not within any defined building area;
c. the disposal area is not within any area required for the disposal of sewage;
d. the disposal area is not within any access strip; and
e. not more than 50% of the site is impervious surface the drainage and disposal of sewage or trade waste
No properties overlook the site, and all completed works will remain surrounded by significant bush and trees. The WWTP and outfall pipeline will therefore have minimal visual impact on the surrounding area.
Performance Criteria 5
(a) A site or each lot on a plan of subdivision must drain and dispose of stormwater –
(i) to accommodate the anticipated stormwater
a. a. currently entering from beyond its boundaries; and
b. from the proposed development;
(ii) without likelihood for concentration on adjacent land;
(iii) without creating an unacceptable level of risk for the safety of life or for use or development on the land and on adjacent land;
(iv) to manage the quantity and rate of discharge of stormwater to receiving waters;
Being as the proposal complies with the Acceptable Solution 5 the Performance Criteria 5 becomes redundant.
(v) to manage the quality of stormwater discharged to receiving waters; and
(vi) to provide positive drainage away from any sewer pipe, onsite sewage disposal system, or building area; or
(b) It must be unnecessary to require the drainage and disposal of stormwater
26.4.2 Location and configuration of development
Objective
The location and configuration of development is to provide a reasonable consistency between sites for setback from a frontage, height of buildings, and location within the landscape
The location and configuration of the development complies as demonstrated in the following prescribed Acceptable Solutions.
Acceptable Solution 1
A building or a utility structure must be setback from the frontage –
(a) Not less than 20.0m; or
(b) If the development is for sensitive use on land that adjoins a road specified in Table 1 to this clause, not less than the setback specified from that road;
(c) not less than 10.0m from each side boundary; and
(d) Not less than 10.0m from the rear boundary;
(e) or in accordance with any applicable building area shown on a sealed plan of subdivision
Appendix A – Site Plans
The 20m setback requirement to the frontage of the lot is exceeded by 127.38m.
n/a
The 10 m side setback requirement is exceeded by 100m on the eastern side and 94.68 on the western side.
The 10m rear setback requirement is exceeded by 55.3m.
The location of sensitive use development on rural land does not unreasonably interfere with or otherwise constrain –
1) agricultural land for existing and potential sustainable agricultural use dependent on the soil as a growth medium;
(b) agricultural use of land in a proclaimed irrigation district under Part 9 Water Management Act 1999 or land that may benefit from the application of broadscale irrigation development;
(c) use of land for agricultural production that is not dependent on the soil as a growth medium, including aquaculture, controlled environment agriculture, and intensive animal husbandry;
(d) conservation management;
(e) extractive industry;
(f) forestry; and
(g) transport and utility infrastructure
This section of the Planning Scheme is not applicable, as the intended use is not a sensitive use, as defined by sub-section 4.1.
3.2.2. Geology, Geomorphology and Soils including Land Stability
The proposed WWTP site is located on the following geology according to Tasmania’s Listmap:
Table 8 – Surrounding Geology
Location Geology Description
WWTP site Qpg Quaternary glacial and glacigene deposits
Steeper area to the north Qpgg Pleistocene glacial and glacigene deposits
130 metres width centred
around the Stitt River
Cdt Cambrian upper sequence of felsic to intermediate
volcaniclastic and volcanic rocks, with sedimentary units of
Cambrian Series 3 – Furongian age. Tyndall group and
correlates.
In September 2013, GeoTon completed geotechnical site investigations across the site. Their report
titled “Geotechnical Investigation and Landslide Risk Assessment - Proposed Sewer and Water
Works in Rosebery” is included in Appendix Q and summarised below:
General WWTP site conditions:
The field data generally confirmed the Mineral Resources Tasmania (MRT) Geology 1:25,000 Scale Digital Sheets information which noted Quaternary aged glacial deposits at the WWTP site, and on the upper slopes with Cambrian aged volcaniclastics located on the lower slopes towards the Stitt River.
The site is not within an area mapped for landslide hazards by MRT. However, the steep slopes at the location of the proposed outfall pipeline display past landslide characteristics. The remainder of the site is considered to have a LOW landslide hazard risk provided the construction follows good hill practices.
7 test locations (TP44 to TP50) were excavated at the proposed site of the WWTP, with the subsurface conditions encountered being somewhat variable. The test pits typically encountered topsoil to depths of 0.1m to 0.2m, overlying sandy silt or silty gravel to depths of 0.25m to 1.0m, underlain by varying weakly cemented units of sand, gravel, silt and cobbles/boulders to the investigated depths of 1.0m to 2.0m.
Test locations TP48, 49 and 50 were terminated at depths of 1.0m to 1.2m due to excavator refusal on strongly cemented gravel and cobbles.
Minor groundwater seepage was encountered above the cemented soils (perched water table) in test locations TP44, 47 and 50.
Trenches:
Trench excavations through this section should be readily achievable for most of the alignment with an excavator of about 20 tonne, however some areas of large boulders and strongly cemented soils (TP48, 49 and 50) may require larger excavating equipment or possible rock breaking.
Excavated natural material would generally be suitable for trench backfilling. Larger cobbles and boulders encountered in trench excavations may not be suitable to be used within the trench backfill and will need to be disposed off-site.
We consider the slopes for the proposed WWTP possess a LOW slope stability risk.
WWTP Foundations:
The WWTP site has been classified as CLASS A (AS 2870 - 2011– Residential Slabs and Footings) based on the ground conditions encountered at the time of the site investigations.
Conditions at this site dictate that the founding medium for all footings should extend through the loose topsoil and sandy silt soils onto the weakly cemented soils or better.
Pad or bored pier footings founded within the weakly cemented soils at depths below 0.3m to 1.0m may be proportioned to an allowable bearing pressure of 250kPa.
Preliminary site pad earthworks and foundation preparation has been undertaken including excavation, stripping of topsoil and importing and compaction of 300mm depth of gravel.
Outfall Pipeline:
The hill slope is densely vegetated with native forest and a track has been cleared along the proposed alignment.
The hill slope typically has slope angles between 25 and 38 degrees and is undulating in the steeper sections with evidence of several shallow landslide features. In addition, the proposed alignment crosses two minor drainage depressions that show evidence of land instability with shallow landslide features.
The test locations on the upper slopes (BH39 and BH42) encountered topsoil and sand to depths of 0.2m and 0.3m, overlying sandy silt to auger refusal on inferred cemented soils at depths of 0.6m and 1.1m.
The test locations on the lower slopes (BH40 and BH41) encountered topsoil to a depth of 0.2m, overlying clayey silt to depths of 0.5m and 0.6m, underlain by gravelly clayey silt to auger refusal on inferred weathered rock at depths of 0.7m and 0.75m.
No groundwater seepage was encountered over the investigated depths. However, groundwater seepage is expected in the drainage depressions along the proposed alignment, and subsoil drains will be required through the drainage depressions to discharge water downslope of the pipeline.
Figure 5 below summarises the geotechnical information relating to the WWTP site and proposed outfall pipeline: (Note - All boreholes have been purpose drilled for geotechnical assessment for the Rosebery WWTP development)
Figure 5 – GeoTon Site Plan - Proposed WWTP and Outfall Pipeline (Re: Fig 2 in GeoTon report)
In addition to the geology, the area is located and surrounded by the following geoconservation
sites according to Tasmania’s listmap:
Within - Central Highlands Cainozoic Glacial Area (Id 2953)
To the east - Rosebery - Hercules Alteration and Mineralisation (Id2963)
To the south – Western Tasmania Blanket Bogs (Id 2527) There are no proclaimed landslip zones within the proposed site. There is also an extremely low risk of inland acid sulphate soils along the banks of the Stitt River.
Two separate assessments relating to flora and fauna have been considered as part of this project as
follows:
1. Terrestrial – at the WWTP site, access road and outfall pipeline alignment
2. Aquatic – in the vicinity of the proposed outfall pipe along the Stitt River
3.2.3.1. Terrestrial Flora and Fauna Assessment
In May and June 2013, CMW engaged ECOTas to prepare an “Ecological Assessment for the
Proposed Rosebery Wastewater Treatment Facility, Stitt River, Rosebery, Tasmania”. A copy of this
report is included in Appendix P.
The proposed development will result in the clearing of probably less than 2 ha of native vegetation
within the context of a modified and managed landscape. The assessment of the proposed
development area and immediate surrounds that may be affected by the installation and operation
of the wastewater facility were assessed in accordance with recognised guidelines.
No ecological values of high conservation significance requiring specific management under local,
State and Commonwealth government legislation and other policy instruments were identified.
No formal referral to the relevant State or Commonwealth government agency under the provisions of the Tasmanian Threatened Species Protection Act 1995 or the Commonwealth Environment Protection and Biodiversity Conservation Act 1999, respectively, are considered necessary. A summary of key findings from the desktop and field investigations are: Non-priority flora and fauna (e.g. species of biogeographic significance):
No species of high conservation significance were detected, and no special management actions are required.
Threatened fauna:
Potential habitat is present for the Tasmanian devil, spotted-tailed quoll, grey goshawk, and masked owl, however field survey did not indicate actual presence of these species
The presence of potential habitat of these species should not constrain the proposed development.
NOTE: More specific discussion on the Tasmanian devil is included in Section 3.2.3.2 below. Threatened flora:
No plant species, listed as threatened on the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 were detected within the study area, and no special management actions are required.
No plant species, listed as threatened on the Tasmanian Threatened Species Protection Act 1995, were detected within the study area, and no special management actions are required.
Vegetation types: The study area supports four native TASVEG mapping units:
“Eucalyptus obliqua forest over rainforest” (TASVEG code: WOR); and
“Eucalyptus nitida forest over Leptospermum” (TASVEG code: WNL);
The study area supports one exotic non-forest TASVEG mapping unit:
“extra-urban miscellaneous” (TASVEG code: FUM).
None of these mapping units are classified as threatened under Schedule 3A of the Tasmanian Nature Conservation Act 2002, or on schedules of the Commonwealth Environment Protection and Biodiversity Conservation Act 1999, and no special management actions are required.
The clearance of the estimated extent of these vegetation types will not compromise the provisions of the Tasmanian Permanent Native Forest Estate policy, and no special management actions are required.
Weeds and disease:
Four species, classified as a “declared weeds” within the meaning of the Tasmanian Weed Management Act 1999, were detected from the study area. Two other “environmental weeds” within the meaning of Schedule 1 of the West Coast Planning Scheme 1999 are present. Two additional exotic species of potential concern but not formally classified under the Act or Scheme are also present.
No evidence of plant disease (Phytophthora cinnamomi, rootrot fungus; myrtle wilt) was detected: the former is unlikely to be a significant management issue but consideration of minimising the risk of introducing myrtle wilt is recommended.
The study area is within a “data hole” with respect to records of frog chytrid disease. It is recommended to assume that the disease is absent and to manage construction and operation of the facility to minimise the risk of introducing the pathogen.
Detailed recommendations are provided in relation to the management of the identified ecological values including weed and disease issues. These are included in Appendix H of the ECOTas report, and also detailed in Section 4.7 of the DPEMP.
3.2.3.2. Tasmanian Devil Impacts
During desktop assessments and on advice from the EPA, the need to assess potential Tasmania
Devil habitat was highlighted. Due to the Tasmania Devils facial tumour disease, numbers have
decreased to such an extent that they have been listed as an endangered species under the
Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC).
The ECOTas report specifically assessed the potential impact of the WWTP on the Tasmanian Devil. The field survey concluded that:
Evidence of Tasmanian Devil was not found,
There is no need for a more formal site survey ie. camera-trapping at this site, and
The presence of potential habitat for the Tasmanian devil should not constrain the proposed development.
3.2.3.3. Aquatic Flora and Fauna
In June 2011, MMG completed a report titled “Biological Condition of the Ring and Stitt Rivers:
Survey of Aquatic Biota spring 2010 and autumn 2011”as part of their environmental obligations
given its upstream mining operations. A copy of this report is included in Appendix L1. This report
has been used as background information to help set ambient stream condition along the Stitt River.
The first 8 months of data is detailed in Appendix K2 and summarised below in Table 9 and
compared with relevant ANZECC guidelines:
Table 9 – Comparison of AMP data to ANZECC Trigger Values
Parameter ANZECC default trigger values for physical and chemical stressors for SE Australia (Lowland River)
Comments
Ph
ysic
al/C
he
mic
al S
tre
sso
rs
pH 6.5 - 8 No issues at any sites, all within stressor limits.
Turbidity 6 -50 NTU No issues with a maximum of 4 NTU at all sites
Conductivity A. Stitt River (highly modified waterway) = 90 µS/cm-1
B. Lake Pieman (stressor level) = 30 µS/cm-1
Fine in the Stitt River with a maximum 80%ile of 83 µS/cm-1, which is below the stressor level, however in Lake Pieman there is a maximum 80%ile of µS/cm-1, which is above the stressor level in this waterway.
Nitrogen 500 µg/l
80%ile readings similar to stressor levels at all sites.
NOx (Oxides of N)
10 µg/l
80%ile readings more than double stressor levels at some sites.
Phosphorus 50 µg/l
80%ile readings similar to stressor levels at all sites.
Dissolved reactive P
20 µg/l
80%ile readings just below stressor levels at all sites.
95
% S
pe
cie
s P
rote
ctio
n T
oxi
can
t Tr
igge
r Le
vel
Aluminium 55 µg/l (toxicant level)
At least 316 µg/l(toxicant level) in the Stitt River which is significantly higher than the toxicant level and slightly less in Lake Pieman.
Cadmium 0.2 µg/l (toxicant level)
At least 0.7 µg/l(toxicant level) in the Stitt River which is significantly higher than the toxicant level, and slightly less in Lake Pieman.
Copper 1.4 µg/l (toxicant level)
At least 6.8 µg/l(toxicant level) in the Stitt River which is significantly higher than the toxicant level, and slightly less in Lake Pieman.
Ammonia 10 µg/l (toxicant level)
Well below toxicant levels at all sites.
Lead 3.4 µg/l (toxicant level)
At least 20.7 µg/l(toxicant level) in the Stitt River which is significantly higher than the toxicant level, and slightly less in Lake Pieman.
Zinc 8 µg/l (toxicant level)
At least 825 µg/l(toxicant level) in the Stitt River which is significantly higher than the toxicant level of 8, and slightly less in Lake Pieman.
NH
MR
C
Re
cre
atio
nal
Lim
it
Entrococci 140 CFU/100ml 80%ile of 10 CFU /100mL at all sites, well below a guideline
Some forms of nitrogen and phosphorus, and all heavy metals are at or higher than ANZECC stressor
or toxicant levels. The high heavy metals in the Stitt River were not unexpected due to ongoing
In all 3 cases the minimum flows occur in February and the maximum flows in August, which is
consistent with the BOM monthly rainfall data summarised in Table 11 above. These are
summarised in Appendix K4 and below:
Table 11 – Stitt River Flow Data m3/s (kL/s) (Hydro Tasmania – 1991 to 2012)
Channel Flows Average Annual Minimum
(February)
Maximum
(August)
Average 2.37 0.83 3.99
Minimum 0.36 0.16
Lowest flow 0.066 (Feb 01)
0.62
Maximum 24.8 14.6 34.4
4.1.5. Mixing Zones
Under Section 20.1 of Tasmania’s State Policy on Water Quality Management 1997 (SPWQM), a
mixing zone around the point of discharge can be defined if it is “not reasonable or practical to
reduce the levels of pollutants in an emission to the levels which would be required to achieve the
water quality objectives for the receiving waters at the point of discharge.” Section 2.8 of the
DPEMP discussed alternative options to minimise discharge to the environment, and this could not
be achieved, and therefore a discharge into the Stitt River is proposed.
Under Section 20.3(f) of the SPWQM, “mixing zones in rivers, streams and estuaries should be set having regard to the effects of the mixing zone under low flow conditions”. In June 2013, Macquarie
Franklin prepared a report titled “ Stitt River Stream Flows Proposed Rosebery WWTP Outfall”. A copy is
included in Appendix K3. This flow monitoring at 15 minute intervals was specifically undertaken to determine
the following:
• To quantify the impact of significant water extraction from the river from MMG for mine operations
since this occurs downstream of the permanent Rosebery monitoring station
• Minimum flow conditions expected along the Stitt River at the proposed outfall location. This was
ideal timing given Rosebery had a very dry summer with low rainfall.
Mean rainfall for the January to March period in Rosebery (Gepp Street Site 097089) is 303.7mm, and only
280.4 fell to the end of March (92%).
Based on Taswater and Macquarie Franklins (David Krushka & Alistair Brooks) site inspections, collection of stream flow data from 4th to 25th March 2013, and subsequent analysis it was noted that:
Over the three week data collection period a very good flow correlation occurred between the permanent Stitt River gauging station upstream of Rosebery (the ‘Taswater’ station) and the temporary installed gauging station at the proposed WWTP outfall;
At the start of the data collection period velocities in the river at the WWTP outfall location appeared much lower than normal typical summer velocities due to the very low rainfall period leading up to this date. This data therefore provides a good indication of worst case mixing zones since this is expected to reflect minimum flows along the Stitt River.
The velocity in the river at the end of the data collection period appeared more typical of summer velocities for the Stitt River.
For future comparison of very low river flows between the two locations, it should be noted that the pumps for the town water supply and mine are downstream of the permanent Taswater station, therefore there will be less flow in the river at the proposed WWTP outfall compared to the permanent Taswater site when the flows in the river are very low. However, as the flows in the river increase and the town and mine pumps have less effect on the percentage of flow in the river, flows at the temporary station end up being greater than the Taswater station due to the larger catchment area at the WWTP outfall location.
During this monitoring the following flow data was recorded:
Table 12 – March 2013 Flow Monitoring in Stitt River at WWTP Outfall Site
Flow conditions Flow rate (l/s) Mean Velocity (m/s) Mean River Depth (m)
Extreme dry weather low flow (5th
to 10th
Mar)
72.9 0.0192 0.603
“more typical” summer conditions
(10th
to 25th
Mar)
1,943.1 0.343 0.644
Based on the range of effluent discharge rates from the WWTP (as listed in Table 2 in Section 2.2.1,
the following dilutions factors are expected:
Table 13 – Expected Dilution in Stitt River at WWTP Outfall Site
Effluent Flow
condition
Influent
Discharge
rate (l/s)
Mixing Zone
Dilution (1 in ...)
Minimum Summer
flow 72.9 l/s 1
Mixing Zone
Dilution (1 in ...)
Minimum Summer
flow 66 l/s 2
Mixing Zone
Dilution (1 in ...)
Average Summer
flow 1,943 l/s 1
Mixing Zone
Dilution (1 in ...)
Average Year flow
2,295 l/s 3
Minimum ADWF 1.5 49 5 44
5 1,295 1,530
ADWF per ET 2.8 26 5 24
5 694 820
Minimum inflow 4.7 15 5 14
5 409 484
ADF 18.5 4 4 4
4 105
4 124
4
Average inflow to
WWTP
37.0 2 4 2
4 52
4 62
4
Peak inflow to
WWTP (Max. duty
at Park Road SPS)
47.0 Not determined since if occurs, all flows in excess of 37 l/s will be bypassed at the
WWTP with partial treatment only, when flows along the Stitt River will also be high.
This is discussed in more detail in the risk assessment in Section 4.1.6.
NOTES:
1. Measured Stitt River flows from 2013 Macquarie Franklin report (Refer Appendix K3)
2. Measured by Hydro Tasmania in February 2001, HOWEVER this minimum flow may no longer be relevant
depending on what mine extraction rates and WTP inlet rates were occurring at the time (Refer Appendix K4)