ECOLOGICAL IMPACT ASSESSMENT · Eco Logical Australia Pty Ltd 39 Ecological Assessment, GIS,...

Environmental Investigation and Assessment – Killick Creek Strategy H (November 2008)

Eco Logical Australia Pty Ltd 36 Ecological Assessment, GIS, Environmental Management and Planning

7. ECOLOGICAL IMPACT ASSESSMENT

7.1 Introduction

Kempsey Council require an Environmental Impact Assessment (EIA) of the proposed dredging activities associated with Strategy H of the Killick Creek EMP. The aims of the EIA are to:

• Detail the type, location and condition of marine and terrestrial vegetation within the study area;

• Detail any aquatic habitats within the study area;

• Identify any threatened species, populations, and/or ecological communities known from or likely to be found within the area;

• Assess the likely impact of the proposed activity on the surrounding environment and species; and

• Conduct physio-chemical water testing including assessing water column stratification.

For the purposes of this impact assessment, the subject site is defined as the proposed dredging and disposal sites (aerial and aqueous). The study area is defined as the broader area of Killick Creek and its banks, which surround the subject site.

7.2 Methodology

7.2.1 Data audit and literature review

A review of available literature and aerial photographs was undertaken to ascertain the extent and type of vegetation, aquatic habitat and threatened species present within the study area. Literature reviewed included:

• Killick Creek Estuary Management Study and Plan

• Killick Creek Estuary Processes Study

• Report on Fish Kill at Crescent Head, NSW

• Biological and Hydrological Status of the Creek: Causes and Recommendations Regarding Oxygen Depletion.

A desktop search for threatened species known to or with potential to occur at the site was undertaken on 13th July 2008 using the following databases:

• Atlas of NSW Wildlife

• EPBC Protected Matters Search Tool

Searches were based on a 10 kilometre radius from the centre of the site: 31.18625oS,152.9749oE. Appendix 6 presents the threatened species identified by the database searches together with an assessment of the likelihood of occurrence of each species at the site.



The likely occurrence of threatened species within the study area was determined by records in the area, habitat available and knowledge of the species’ ecology. Five terms for the likelihood of occurrence of species are used in this report. The terms for likelihood of occurrence are defined below:

• ‘Yes’ = the species was or has been observed on the site.

• ’Likely’ = a medium to high probability that a species uses the site.

• ‘Potential’ = suitable habitat for a species occurs on the site, but there is insufficient information to categorise the species as likely to occur, or unlikely to occur.

• ‘Unlikely’ = a very low to low probability that a species uses the site.

• ‘No’ = habitat on site and in the vicinity is unsuitable for the species.

7.2.2 Field surveys

Field surveys were carried out from 21-23 July 2008 by Dr Ailsa Kerswell (ELA). The aims of the site inspection were to:

• Determine the type, location and condition of all marine and terrestrial vegetation within the study area;

• Identify any aquatic fauna habitats within the subject site;

• Identify any threatened species, populations or endangered ecological communities known to occur or likely to occur within the study area; and

• Undertake physio-chemical water sampling across the subject site.

Aquatic surveys were undertaken at the dredging and aqueous disposal sites. Surveys included a visual assessment of aquatic habitat features and intensive searches for aquatic vegetation, including mangroves, seagrass and macroalgae. Surveys for aquatic vegetation were performed by systematically traversing the sites and conducting visual searches. Water visibility was good during the field surveys, with the creek bottom visible from the surface across the full area proposed for dredging/disposal. Representative areas of aquatic vegetation were photographed. Opportunistic sightings of aquatic fauna such as fish and stingrays within Killick Creek were recorded. Surveys for macroinvertebrate fauna were performed along the existing rock seawall and in the sandy benthos of the creek. A list of taxa colonising the seawall was compiled based on visual surveys. The composition of benthic invertebrates was surveyed by digging shallow holes at various points throughout the dredging and aqueous disposal sites and identifying the uncovered fauna. Bird surveys of the proposed dredging and disposal areas were undertaken for approximately one hour at dusk on each of the three field survey dates. Terrestrial vegetation type, structure, dominant plant species and condition were recorded at the proposed aerial disposal site and along the banks of Killick Creek adjacent to the proposed dredging and aqueous disposal sites. The boundaries of all vegetation communities were mapped using a Global Positioning System (GPS). Random



meandering transects were undertaken throughout vegetation communities to identify threatened plant species. Physio-chemical sampling was undertaken at a series of points throughout the proposed dredging and aqueous disposal sites (Figure 8). At all sampling points temperature, dissolved oxygen, pH, salinity and turbidity were recorded five centimetres from the creek bed. In order to test for water column stratification, the same parameters were recorded through the water column at ten centimetres depth increments. Field surveys were conducted in warm, sunny conditions with little rainfall in the preceding weeks. During the 3-day field survey period, the entrance to Killick Creek was open only briefly at high tide. Appendix 4 presents the weather conditions at the time of survey as well as the week leading up to survey. The tidal conditions on the day of survey and week leading up to survey are also presented in Appendix 4.

7.2.3 Limitations

This study was conducted over 3-days in winter and focused primarily on recording vegetation communities, aquatic habitat features and the presence of threatened species. Some estuarine processes, such as fish breeding and bird migration, are dependent on season and water flow conditions, and may therefore be missed by a brief assessment. The estuarine environment is dynamic with changes occurring across a range of temporal scales. As such, the habitat features and suitability of the habitat for various flora and fauna will also change. A brief assessment, like the one undertaken in the current study, will not identify all the possible habitat features or mobile/migratory species. To do so would require surveys over periods when the estuary is open and closed to the sea and across the seasons.

7.3 Results

7.3.1 Proposed Dredging and Aqueous Disposal Sites

The proposed dredging and aqueous disposal sites within Killick Creek are similar being shallow, sandy bottomed, saltwater environments. The water upstream of Muddy Arm is tannin stained, but generally clear (see Water Quality results below), however; the entire creek area becomes rapidly turbid following rain and subsequent runoff. At the time of survey, the creek was open to the sea for a short period of time at high tide. The majority of aquatic habitat within the dredging and aqueous disposal sites is submerged, soft sandy bottom and periodically exposed non-vegetated sand flats. Due to the dynamic nature of the Killick Creek environment, the exact area and location of each of these habitats (i.e. submerged versus exposed areas) will change over time depending on the tidal and upstream flow conditions. Both these habitats typically support a diverse assemblage of benthic invertebrates which in turn support a range of fish and wading bird species (DPI, 2006). Killick Creek downstream of Muddy Arm (i.e. the downstream area of the disposal site) is a highly dynamic environment. Over the course of the field study, the location and degree of exposure of sand shoals within the Creek changed noticeably. Similarly, deep pools (to approximately 0.8 metres depth) were observed at various, changing locations within the creek. Deep pools offer refuge for fish and other aquatic organisms during times of reduced flow were observed and provide important temporary habitat to fish trapped in the creek during low tide.



The existing sea wall adjacent to the dredging site provides aquatic habitat in the form of rock crevices and rocky substrate on which aquatic organisms, such as molluscs can attach. The degraded nature of the sea wall means that it also contributes indirectly to aquatic habitat by spilling small to medium rocks into the channel. The base of the seawall provides complex habitat that is used as a refuge for juvenile fish. Aquatic vegetation is sparse within the study area. Seagrass has been reported to occur in Killick Creek (West et al., 1985), however during the present field investigation only very limited patches (4-5 patches of <0.5m2 each) were observed within the dredging and aqueous disposal sites. The seagrass (Zostera capricorni) was in very poor condition, with heavy epiphyte infestation (Figure 7A). No macroalgae was observed in the creek, although summer blooms of ‘Red Weed’ have been recorded as a significant issue for Killick Creek (WBM Oceanics Australia, 2006). Grey Mangroves (Avicennia marina) are found in low to moderate densities at both the aqueous and aerial disposal sites. Mangroves within the aqueous disposal site are experiencing dieback (Figure 7B), and no mangrove recruits / saplings were observed at the site or within the surrounding area. Both live and dead mangroves provide significant aquatic habitat within the aqueous disposal site. Mangrove roots and woody debris provide important shelter, substrate for colonisation and food for a host of aquatic organisms, including juvenile fish. In addition, woody debris can aid in stabilisation of creek channels and can protect creek banks from erosion.

Figure 7: Photographs of seagrass (A) and mangroves (B) located at the aqueous disposal site. Note that both are in very poor condition.

7.3.2 Proposed Aerial Disposal Site

The aerial disposal site is a relatively open area with extensive grassy groundcover (Spinifex sericeus). The site is located at the interface of several vegetation communities (Figure 8) and is in poor condition due to invasion by exotic species and human influences including trampling and rubbish dumping. All native communities are represented by few



individuals with low species diversity, and include mangroves, Coastal Saltmarsh and Swamp Oak Floodplain Forest. The mangroves located within the aerial disposal site occur above the high tide mark and are growing in areas of grassy ground cover (Spinifex sericeus). These mangroves are stunted, growing no taller than 1.5 metres. The coastal saltmarsh community is represented by sparse patches of rushes, predominantly Juncus kraussii, located within the grassy areas. There is low diversity of saltmarsh species compared to other areas of coastal saltmarsh located to the west and south of the aerial disposal site. The proposed aerial disposal site also contains Swamp Oak Floodplain Forest (SOFF). The SOFF is a small pocket of approximately 25 trees indicative of that community including Casuarina glauca, Glochidion ferdinandi var. ferdinandi and Melaleuca quinquenervia. The mid- and ground-story are dominated by grass (Spinifex sericeus) and exotic species including Bitou Bush (Chrysanthemoides monilifera), Asparagus Fern (Myrsiphyllum scandens) and Fairy’s Tables (Hydrocotyle bonariensis). Coastal Saltmarsh and SOFF are listed as endangered ecological communities (EEC) under the TSC Act (Coastal Saltmarsh in the NSW North Coast, Sydney Basin and South East Corner Bioregions, Swamp Oak Floodplain Forest of the NSW North Coast, Sydney Basin and South East Corner bioregions) (refer to Appendix 8).



Figure 8: Vegetation communities at the proposed disposal sites and surrounding area.



7.3.3 Adjacent Environment

The dredging and disposal sites are fringed by Coastal Saltmarsh, which grows on the sandy flats above the high tide mark. This community is dominated by tall rushes (Juncus kraussii) and is in good condition in the areas north of Muddy Arm and south of the proposed aerial disposal site. There is a relatively high diversity of species found throughout these saltmarsh areas, as compared to the isolated patches of rushes found in the aerial disposal site (see Appendix 5 and 6 for a list of species). Moreover, examination of aerial photographs, suggests that the extent of the Coastal Saltmarsh community has increased, particularly on the south-eastern bank of Killick Creek opposite the proposed dredging site. The terrestrial vegetation upstream of Muddy Arm and adjacent to the proposed dredging site is designated as a SEPP 14 Coastal Wetland, which is fringed by Coastal Saltmarsh EEC (Figure 8). While Grey Mangroves (Avicennia marina) are found in low densities within the proposed disposal sites, there is a large stand of trees approximately 250 metres upstream of the northern tip of the disposal site (Figure 8). The majority of mangroves in this area are experiencing dieback (Figure 9). Examination of aerial photograph sequences from 2001 to the present, show that the mangrove stand was previously located on a mudflat, which extended into Killick Creek. Today, this mudflat and the mangroves are permanently inundated, suggesting water-logging as the most likely cause of the mangrove dieback.

Figure 9: Mangrove dieback north of proposed disposal sites.



7.3.4 Fauna Species

More than 26 taxa were sighted during the field surveys within the study area, including >16 aquatic taxa and 10 bird species. The majority of birds sighted were actively foraging on the sandy flats of Killick Creek at both the proposed dredging and disposal sites. At any one time, the number of birds foraging within the creek was low (<10 individuals). However, it should be noted that both the number of birds and the diversity of species found at Killick Creek is likely to be higher in summer when migratory birds are present in the southern hemisphere. Previous studies have indicated a high diversity of fish within Killick Creek (Manly Hydraulics Laboratory, 2002) with 26 species sampled during surveys in 1993. While targeted fish surveys were not undertaken as part of the current field study, incidental observations support the previous results. Numerous fish species were observed in the creek including both adult and juvenile life stages. Several schools of juvenile fish were observed to be utilising the ephemeral deep pools and rock wall crevices as habitat and refuge from foraging birds. The lower reaches of Killick Creek were also used by larger fish as a low tide refuge. Stingray feeding pits (shallow depressions in the sand left when rays settle on the bottom and feed on benthic infauna) were common throughout Killick Creek and one large ray (~60cm diameter) was observed feeding in the creek at low tide. Previous studies have also surveyed the macroinvertebrate communities of Killick Creek and concluded that they are typical of those found in NSW sandy estuaries (UNE 1993, Manly Hydraulics Laboratory 2002). The results of this study confirm those of previous studies. The rock wall provided complex habitat for numerous molluscs primarily the Sydney Rock Oyster (Saccostrea commercialis) and a common marine snail (Bembicium nanum). Sandy bottom habitats contained numerous infauna including polychaete (beach) worms, crabs, yabbies and bivalves species. Densities of these taxa were not quantified, however, numerous shorebirds, fish and stingrays were observed feeding within the sandy sediments suggesting healthy populations of macroinvertebrate infauna.

7.3.5 Flora Species

In total, 23 plant species were recorded growing within or immediately adjacent to the study site. The majority of species were sedges and rushes associated with the Coastal Saltmarsh, however some tree species were also present. Common native species included Acacia longifolia var. sophorae, Casuarina glauca, Juncus kraussii and Spinifex sericeus. Bitou bush (Chrysanthemoides monilifera) was common on the front dunes. The marine plants Avicennia marina and Zostera capricorni were both found in Killick Creek, but were in poor condition and, in the case of the seagrass, in low densities.

7.3.6 Threatened Species

No threatened plant species were found at the study site during the field surveys. Five threatened plant species have been recorded within 10 kilometre of Killick Creek (Appendix 6), however all but one (Sand Spurge) are not associated with coastal dune or wetland habitat. Sand Spurge (Chamaesyce psammogeton) grows on fore-dunes and exposed headlands, often with Spinifex and therefore potentially occurs within the aerial disposal site. Database searches for threatened fauna list 64 species that occur within a 10 kilometre radius of Killick Creek. Five threatened bird species (Ephippiorhynchus asiaticus, Haematopus fuliginosus, Haematopus longirostris, Ixobrychus flavicollis, Pandion haliaetus)



have been recorded at the Killick Creek study site and one other (Sterna albifrons) is likely to occur. Pristis zijsron (Green sawfish) has the potential to occur within Killick Creek. This species prefers shallow estuaries on sandy or muddy bottoms, such as those found in Killick Creek. A search of the Commonwealth DEWHA Protected Matters database indicated 46 marine and/or migratory EPBC Act-listed species occur within a 10 kilometre radius of Killick Creek. These include 19 fish, 2 reptiles, 12 mammals and 13 birds and are in addition to other marine or migratory species which have an endangered or vulnerable listing (Appendix 7). Of these, two bird species (Haliaeetus leucogaster and Ardea alba) were sighted during field surveys. Additionally, the Double-ended Pipehorse (Syngnathoides biaculeatus) was caught in a previous fish survey of Killick Creek. Consequently, all other pipefish and seahorses listed on the EPBC Act are considered to potentially occur within Killick Creek.

7.3.7 Water Quality

No evidence of water column stratification was found at the water quality testing sites in Killick Creek, with values for physio-chemical parameters consistent throughout the water column at all sites. Water quality measurements were taken during low tide when the creek was closed to the ocean. As a consequence, values for salinity and pH were slightly lower than those of the nearby open ocean, reflecting the freshwater influence of upstream flows. The salinity and pH values recorded during the field study are within the ANZECC guidelines for estuarine systems. Dissolved oxygen (DO) levels within Killick Creek are lower than the recommended ANZECC water quality guidelines (80-110%). Values in Killick Creek ranged from 61-77%. Dissolved oxygen levels in Killick Creek are generally lower at low tide (UNE 2003), and thus the values reported here are likely to be towards the lower end of DO range. Low DO levels have been highlighted as an on-going problem in Killick Creek (UNE 1993, Manly Hydraulics Laboratory 2002) and have been attributed to either oxygen-consuming decomposition within upstream Belmore Swamp or of red algae trapped in Killick Creek. In this instance, no algae was observed in Killick Creek suggesting dissolved oxygen problems stem from upstream influences. Turbidity was low during the study period when there had been little rainfall in the preceding days (refer to table 4). However, heavy rain fell in the Killick Creek catchment on the days after the field survey (44mm on 23rd-24th July 2008) and the creek rapidly became turbid as tannin-rich water flowed downstream. Water quality parameters are likely to vary when the creek is permanently open to seawater incursions.



Table 4: Water quality results

Depth DO DO Salinity Temp Turbidity Testing site Easting Northing

(m) (mg/L) (%) pH

(PSU) (oC) (NTU) 132 497759 6549571 0.26 5.56 63 7.89 29 13.3 0 133 497722 6549608 0.42 6.04 67 7.87 28.8 12.75 0 134 497670 6549670 0.74 5.6 63 7.97 28.8 12.59 0 135 497611 6549753 0.49 6.5 74 7.96 28.6 12.48 0.1 136 497558 6549819 0.18 5.9 68 7.85 28.1 13.85 0 137 497539 6549868 0.49 5.9 68 7.85 27.8 13.66 4 138 497526 6549919 0.43 5.7 67 7.84 27.9 13.29 0.1 139 497519 6549967 0.64 5.4 61 7.85 27.9 13.27 0.7 140 497494 6550017 0.61 5.5 63 7.8 27.7 13.77 0.6 141 497473 6550068 0.75 5.37 62 7.8 27.7 14.09 0.5 142 497662 6549874 0.16 6.63 77 7.97 27.8 13.96 0.5 143 497659 6549952 0.73 5.95 69 7.89 27.9 13.6 1.2 144 497621 6550052 0.52 6.03 68 7.85 27.5 13.07 1.6 145 497568 6550108 0.49 6.07 69 7.83 27.8 13.96 1.6

7.4 Impact Assessment

The impacts of the activities proposed under Strategy H will be associated with both dredging and spoil disposal. Direct impacts of the proposed works are likely to include:

• Habitat disturbance associated with site access, sediment extraction and spoil disposal.

• Increased turbidity in Killick Creek during dredging and aqueous disposal1.

• Smothering of taxa by dredge spoil.

Indirect impacts associated with the proposed works are likely to include:

• Alteration to flow regimes2.

• Exposure of potential acid sulfate soils.

1Increased turbidity of the creek during dredging may cause concern for the Crescent Head community. It is recommended that Council consult with local residents prior to the commencement of dredging regard increased turbidity in the creek to reduce the likelihood of a problematic public perception issue. 2 Note that alteration to natural flow regimes is listed as a Key Threatening Process under the TSC Act. However, given the long history of hydrological modification to Killick Creek and the presence of upstream floodgates, dredging of Killick Creek is not deemed to fall into the category. The purpose of the proposed dredging activity is to maintain the tidal and flood hydrodynamic conditions that have characterised the estuary for the past 30 – 50 years.



7.4.1 Impacts to aquatic habitats

The major aquatic environment within Killick Creek is soft, sandy bottom. This environment is highly dynamic, with sand shoals and deeper pools forming and dissipating on a regular basis. Additionally, sediments from the dredge site will not be markedly different from those found at the disposal location. Dredging Killick Creek and disposing of the spoil at the aqueous disposal site will alter the location and depth of the aquatic environment. However given the constantly changing nature of the estuary, movement of sediment is unlikely to alter the habitat value of the soft, sandy bottom. There are no extensive seagrass or macroalgal beds within the dredging or disposal sites. Within the impacted sites estuarine vegetation is limited to very small isolated patches of seagrass which is in poor condition. Mangroves occur within the aqueous disposal site; however most are dead or in poor condition. Disposal of dredge spoil around the mangroves will not impact the mangrove plants, given their current condition. Build up of sediment around the dead mangroves may reduce the complexity of habitat available to fish and other aquatic organisms using the mangrove roots / woody debris as a refuge. However, the density of mangroves within the aqueous disposal site is sparse compared to a large stand of dead mangroves located approximately 250 metres north of the aqueous disposal site. This area will not be impacted by spoil disposal and can provide habitat for any organisms displaced by spoil disposal. Thus, the total area of complex aquatic habitat available within Killick Creek will not be significantly reduced as a result of the proposed works. Turbidity will increase during dredging and spoil disposal at the aqueous disposal site. The material to be dredged is marine sand and will settle quickly due to its relatively heavy weight (i.e. compared to silts and muds), making the impacts of increased turbidity short-lived. Additionally, high turbidity is not uncommon in Killick Creek, as water clarity rapidly decreases after heavy rain. The impact of increased turbidity will be restricted to fish and birds, who are likely to have increased difficult in locating prey. However, additional foraging habitat that will remain within clear water during dredging operations is extensive, both within Killick Creek and within the adjacent open ocean. Overall, increased turbidity levels during dredging works are unlikely to significantly impact aquatic taxa within Killick Creek. Long-term impacts associated with altered flow regimes within Killick Creek as a result of dredging are likely to have a positive impact on aquatic habitats. Improved tidal exchange will increase the flushing of the estuary and improve water quality. This will also ensure salinity remains within the tolerance limits of marine and estuarine taxa that currently inhabit Killick Creek. Additionally, increased downstream flow of water currently retained in the upper areas of Killick Creek (e.g. towards the floodgate) will improve water quality by reducing residence time. Recession of water levels in the upstream areas may also alleviate some of the problems associated with water-logging of mangrove communities.

7.4.2 Impacts to terrestrial habitats

Impacts to terrestrial habitats will be restricted to the aerial disposal site, where ground-cover plants will be smothered by dredge spoil. The majority of groundcover species are weeds or common sand dune grass (Spinifex sericeus). Spinifex sericeus is common in the area and has the ability to grow through wind-blown accumulations of sand (Beach Protection Authority, 2008). Other groundcover species include rushes (predominantly Juncus kraussii) associated with coastal saltmarsh communities. There is the potential for these plants to be smothered by dredge spoil. However, due to the overall poor condition



of the saltmarsh at the disposal site, relative to other nearby areas of saltmarsh, the impact of dredge spoil disposal on the local Coastal Saltmarsh community is not considered significant (see 7-part test for Coastal Saltmarsh in Appendix 8). Trees located within the aerial disposal site are representative of Swamp Oak Floodplain Forest. These trees are mature and are unlikely to be affected by accumulation of sand around their bases. Acid sulfate soils present a potential impact at the aerial disposal site. Seawater has a buffering capacity such that potential acid sulfate soils will not oxidise if kept wet (as would be the case with aqueous disposal). As dredge spoil from sites with potential acid sulfate soils dries out, it would oxidise and become acidic. This would negatively impact both the flora and fauna at the aerial disposal site. Disposal of potential acid sulphate soil spoil above water at the aerial disposal site is therefore not recommended.

7.4.3 Impacts to benthic communities

Benthic communities will be impacted by dredging and disposal. Dredging impacts will include physical removal, potentially resulting in death of some individuals, and habitat disturbance. As discussed above, Killick Creek is a high dynamic environment, and benthic infauna are likely to be highly adapted to disturbed habitats. If spoil is disposed of at the aqueous disposal site, most benthic infauna will be able to re-establish at the new location given the similarity in conditions between the dredging and disposal sites. The success of benthic infauna re-establishment will rely on dredged sediments remaining wet during transport to the disposal location (i.e. it should not be stock-piled at an aerial location for significant lengths of time prior to disposal). If spoil is disposed of at the aerial disposal site, only very mobile infauna such as crabs are likely to survive, as they can escape the spoil pile and return to more favourable aquatic environments. Overall, the impact of dredging on the benthic communities of Killick Creek is not likely to be significant. Only a relatively small proportion of habitat (i.e. 10,000m3 of sediment) will be disturbed. Similarly, species such as fish and birds that rely on benthic infauna as a food source are unlikely to be affected, given the large extent of similar foraging habitat both within Killick Creek and on the beach at Crescent Head.

7.4.4 Impacts to threatened species

Six threatened birds species occur or are likely to occur within Killick Creek. The species are Ephippiorhynchus asiaticus (Black-necked Stork), Haematopus fuliginosus (Sooty Oystercatcher), Haematopus longirostris (Pied Oystercatcher), Ixobrychus flavicollis (Black Bittern), Pandion haliaetus (Osprey), and Sterna albifrons (Little Tern). The significance of impacts for these species has been assessed according to the NSW DECC Threatened Species Assessment Guidelines using 7-part tests (Appendix 8). The impact of dredging and disposal activities is not likely to be significant for any of the listed species. Other threatened species listed under both the TSC and EPBC Acts are considered unlikely to occur in the proposed dredging or disposal area due to a lack of suitable habitat (see Appendix 6). Therefore the proposed activity is unlikely to have significant impacts to threatened species and further assessment under the TSC Act, or referral to DEWHA under the EPBC Act in not deemed necessary.



7.4.5 Impacts to other matters of NES

Other matters of NES which require consideration include:

• World Heritage sites

• National heritage places

• Wetlands of international importance (Ramsar)

• Migratory species

• Commonwealth marine areas

• Nuclear actions.

Of these matters, only migratory and listed marine species are found within the Killick Creek area. A full listing of the migratory and marine species generated from the search undertaken using the Commonwealth Department of Environment, Water, Heritage and the Arts (DEWHA) EPBC Act Protected Matters search tool and field observations is presented in Appendix 5 and 7, along with an analysis of the likely levels of impact on these species from the proposed project. From this analysis none of the species are likely to be significantly impacted by the proposed project (see below) and a referral to DEWHA is therefore deemed unnecessary. Migratory Birds Migratory terrestrial bird species will be not significantly impacted by the proposed dredging activity. All species have large natural distributions and are found in a variety of areas throughout Australia. Direct impacts on nesting or feeding areas are not expected. Each of the migratory wetland bird species is considered relatively common and widespread, making a significant impact (considered here to be an impact on 1% of the national or international flyway populations) unlikely. None of the migratory marine birds will be significantly impacted by the proposed development. The impact site does not contain ecologically significant proportions or important habitat for any of these species. Migratory/Listed Marine Species The majority of migratory and listed marine species are large animals (e.g. whales and dolphins) that will not enter Killick Creek, and will therefore not be impacted by the proposed dredging. Seasnakes are also listed species, however these animals occur in clear offshore waters, and will therefore not be impacted by the proposed activities. Syngnathids (Seahorses and pipefish) are EPBC Act listed marine species and at least one (Syngnathoides biaculeatus) has been recorded in Killick Creek. These species are found in a variety of habitats ranging from deep reefs to coastal algae, weed or seagrass habitats, or around man-made structures such as jetties or mesh nets. They are also highly mobile and would be able to actively avoid the dredging activities by swimming to other areas of suitable habitat located throughout Killick Creek or within the surrounding near-shore oceanic area. Therefore, syngnathids are unlikely to be significantly impacted by the dredging activities within Killick Creek.

7.5 Mitigation measures

Although the environmental impact of the proposed dredging within Killick Creek is likely to be minimal, additional measures can be implemented to further reduce the likely impacts. These include:



• Dumping dredge spoil at the aqueous disposal site only, to avoid smothering of plants and desiccation of aquatic benthic fauna.

• Disposing of dredge spoil within the aqueous disposal site soon after extraction to avoid desiccation of aquatic benthic fauna and enhance their likelihood of successful colonisation of the eastern side of the creek.

• Dredging during winter months to avoid times of peak migratory bird density and fish spawning.

• Accessing the dredge site via existing access point to avoid impacts on vegetation fringing the creek including saltmarsh communities.

• Dredging when the ocean entrance is open to provide mobile aquatic species with opportunities to move out of affected areas.

• Ensuring that dredging does not impact the stability of the existing rock wall.



8. DREDGING AND DISPOSAL OPTIONS

8.1 Dredging Options

Due to tidal and river flow influences significant sediment shoals have formed within Killick Creek, which is affecting the hydrodynamics of the creek, amenity and potentially water quality. Sediment accumulation at the entrance limits the extent of tidal flushing and ocean exchange within the waterway. Additionally, marine (sand) sediment is also accumulated further upstream, particularly in the flood tide delta between the caravan park and the entrance to Muddy Creek. Hydrographic surveys of Killick Creek in July 2001 were carried out a few months after significant flooding, and thus may represent a relatively scoured condition. A hydrographic survey conducted as part of this project in May 2008 show significant sediment deposits and shoaling in the flood tide delta. Strategy ‘H’ of the EMP for Killick Creek (WBM Oceanics Australia 2006) recommends the removal of sediment shoals in Killick Creek which inhibit tidal flushing and flood water discharge. Removal of sand from a flood tide delta is likely to be a temporary solution (with dredged areas infilling relatively quickly), however, removal works could be optimised to maximise longevity whilst still providing the desired hydrodynamic benefits. In this regard, it is considered that dredging could initially be carried out to restore a deeper channel through the upstream end of the flood tide delta (between the Caravan Park and Muddy Arm), as shown in Figure 1. A volume of approximately 10,000m3 would need to be dredged to achieve desired outcomes. Dredging within the active coastal environment is generally discouraged by the State Government, unless the material can be retained within the coastal compartment. In this regard, it may be possible to dispose of the dredged material locally within Killick Creek or pumped over the dunes to the ocean beach, where it could be used for general beach nourishment. It is understood that this beach has experienced shoreline recession in recent years, and thus would benefit from a local sand nourishment program. Consideration has been given to either relocating the sand shoals in Killick Creek or removing them entirely through a sand extraction or dredging program. Permanent removal has longer term benefits (1-3 years depending on tidal and flood conditions). Eventually the influx of marine sediment from the creek entrance due to tidal and wave action will replace the sediment and shoals will reform over time. Relocation of material within Killick Creek will provide benefits in the shorter term but sand will re-suspend and is likely to return and infill into the channel over a relatively short time period (possibly within 12-18 months). The dredging methods selected at Killick Creek will need to:

• be suitable for the specific site;

• reflect environmental best practice;

• be cost effective; and

• meet statutory requirements.



8.1.1 Dredging Methods

Dredging methods can be divided into two primary categories, hydraulic and mechanical, with each consisting of a variety of equipment types. The dredging method selected for a particular project should be based upon specific site characteristics such as substrate type, site bathymetry, wave energy, contamination potential, and operational feasibility. The dredging options considered to implement Strategy H are:

• Dredging using an excavator based on land or on a pontoon; or

• Dredging using a small hydraulic dredge from on the water.

Excavators Excavators (such as backhoes) are shore-based or pontoon mounted ‘diggers’ which can be used in aquatic environments. Especially suitable where site conditions are difficult, such as shallow waters and confined spaces. Material is excavated and placed either into barges or at a near site location. The depth of Killick Creek will preclude the use of barges, accordingly the use of this type of dredge will require dredging and the subsequent re-handling and transport of the material to the chosen disposal site. Depending on the disposal site chosen this may be possible with the use of further excavator equipment, such as a bulldozer, or by loading into vehicles or trailer equipment. Hydraulic dredging Hydraulic dredges (suction and auger dredges) function much like a vacuum, sucking up a mixture of bottom sediment and water. There are two main types of hydraulic dredges: pipeline and hopper. The size and depth of Killick Creek poses restrictions on the use of these types of dredges, particularly for hopper dredges which will be too large to operate within Killick Creek. Pipeline dredging may be an option. Pipeline dredges consist of a pipeline attached to a dredge, which pumps sediment from the intake pipe directly to the disposal site. This type of system is often used for beach nourishment projects when the dredged material can be pumped directly onto the beach. Small suction dredges can be lowered into place by cranes. This would avoid the need for construction of any access ramp or major disturbance to the creek foreshore. Generally the smallest suction dredges of this type require a draught of 0.6 - 1.0 metres. Additionally, with the use of a pump booster it may be possible to pump sediment over the dune system to a beach or intertidal area. This option will have the added advantage of removing the sediment from the creek system and returning it to the coastal system. Combination A combination of mechanical and pipeline suction dredging may be the most suitable option. A mechanical excavator could be used to create an initial channel area of a depth large enough for a suction dredge to operate. A suction dredge could then be lowered into the Creek (potentially from the western shore). The suction dredge could then dredge the shoals and create an operating channel as it went. Sediment could then be piped to the selected disposal site or over the dunes to re-nourish the ocean beach.



8.1.2 Disposal Site Options

The selection of a dredging method needs to be made in conjunction with consideration and selection of a disposal site (refer Figure 10). Disposal site options considered as part of this project are: Sea disposal In order to dispose of dredge material at sea a hopper or barge would be required with access to the open ocean. The shallow nature of Killick Creek and the considerable sedimentation at the mouth of the creek make this option unrealistic. Aqueous disposal site The aqueous disposal site located on the eastern side of the creek opposite the opening to Muddy Creek (refer Figure 10) presents a feasible and easily accessible option. Impacts on the area are discussed in section 7.4.1. Disposal within an aquatic location has the added benefit of ensuring the PASS can be managed safely and easily. Aerial disposal site The aerial disposal site is located adjacent to the aqueous disposal site (refer Figure 10) on the eastern bank of the river. Impacts from disposal at this site would be minimal (refer section 7.4.2), however, the presence of PASS raises problems that will require further assessment and management. Beach nourishment Through the use of a suction dredge or a combination of suction dredge and mechanical dredging the dredged sand could be pumped (possibly with the use of a booster pump) over the dune system to the beach or intertidal area. The most appropriate location for piping material over the dune system is adjacent to the aerial and aqueous disposal sites where the dune is at its narrowest. A minor swale already exists through this area of dune reducing the height to which sediment would need to be pumped. Disposal into the near shore (marine) environment would be recommended as keeping the material wet will reduce the risks of PASS problems and will enable the sediment to re-enter the coastal system and disperse naturally with tides and currents. This option will have the added advantage of removing the sediment from the creek system and returning it to the coastal system. However, has the disadvantage of costs, which are expected to be significantly greater. This option will require further analysis and consideration by a dredging contractor to determine practical feasibility. Impacts of this option have also not been fully assessed as part of this project and may require further analysis, particularly on impacts to the dune and beach environments. Land disposal/sale Removal of sand from the creek for land disposal or for sale is a potential option. This option has not been examined in detail as part of this project and will require further analysis. Such an option would have similar benefits to the beach nourishment option described above, although obviously the sediment would not be returned to the coastal system.



8.1.3 Indicative Costs and Timeframes

An indicative assessment of costs and potential timeframes was investigated by ELA staff through various contractors. Please note that ELA are not contractors or economic consultants, thus these prices are indicative only based on various contractors and do not represent the best option. On average, a small dredge plant costs approximately $250-$300/hour for use/hire. The plant can be hired from numerous places on the Central Coast of NSW and within Queensland. However, the mobilisation cost of the plant could cost up to $5000.00 or more. Based on a symptomatic maximum of 5000 cubic metres, contractors have specified this could take up to 80-100 hours to complete. This may be more or less depending on the option chosen and the amount of material to be mobilised. Other equipment costs may be incurred depending on the option chosen; either dredging or extraction. This could include additional pumps and pipes or additional land transport.



Figure 10: Potential disposal locations for dredge spoil

En

viro

nm

en

tal I

nve

stig

atio

n a

nd

Ass

ess

me

nt –

Kill

ick

Cre

ek

Stra

teg

y H

(N

ove

mb

er 2

008)

Eco

Lo

gic

al A

ustra

lia P

ty L

td

5

5

Eco

log

ica

l Ass

ess

me

nt,

GIS

, En

viro

nme

nta

l Ma

na

ge

me

nt a

nd

Pla

nnin

g

Tab

le 5

: Dre

dg

ing

and

dis

po

sal o

ptio

n a

naly

sis

D

red

gin

g

me

tho

d

Dis

po

sal S

ite

Op

tion

Envi

ronm

enta

l Im

pa

cts

O

per

atio

nal F

ea

sib

ility

C

osts

Ac

hie

vem

ent o

f St

rate

gy

H O

bje

ctiv

es

Ap

pro

val l

ikel

iho

od

Ae

rial d

isp

osa

l M

od

era

te –

ve

ge

tatio

n

at

ae

rial s

ite is

a p

oo

r c

on

diti

on

EEC

; po

ten

tial

ac

id s

ulp

ha

te s

oils

(P

ASS

) w

ill re

qu

ire

ma

na

ge

me

nt.

Go

od

– a

cc

ess

an

d

site

co

nst

rain

ts s

ho

uld

n

ot

po

se a

pro

ble

m t

o

the

use

of

lan

d o

r p

on

too

n b

ase

d

exc

ava

tors

. Tra

nsp

ort

o

f m

ate

rial f

rom

d

red

ge

site

to

dis

po

sal

site

will

req

uire

a

dd

itio

na

l eq

uip

me

nt.

Go

od

– d

red

gin

g

eq

uip

me

nt

an

d

mo

bili

satio

n c

ost

s w

ill b

e lo

we

r th

an

fo

r hyd

rau

lic

dre

dg

ing

, ho

we

ver,

me

tho

d is

less

e

ffic

ien

t a

nd

will

as

a re

sult

be

slo

we

r.

Go

od

– t

he

ne

ar

sho

re lo

ca

tion

of

the

d

isp

osa

l site

will

like

ly

resu

lt in

win

d a

nd

tid

e a

ctio

n re

turn

ing

so

me

of

the

ma

teria

l to

th

e c

ree

k sy

ste

m

ove

r tim

e.

Go

od

– n

o m

ajo

r o

bst

ac

les

are

e

xpe

cte

d in

o

bta

inin

g a

pp

rova

l.

Aq

ue

ou

s d

isp

osa

l Lo

w –

imp

ac

ts li

mite

d t

o

ba

re s

an

dy

sub

stra

te

an

d p

oo

r q

ua

lity

ma

ng

rove

are

as.

Go

od

– a

cc

ess

an

d

site

co

nst

rain

ts s

ho

uld

n

ot

po

se a

pro

ble

m t

o

the

use

of

lan

d o

r p

on

too

n b

ase

d

exc

ava

tors

. Tra

nsp

ort

o

f m

ate

rial f

rom

d

red

ge

are

a t

o

dis

po

sal s

ite w

ill

req

uire

ad

diti

on

al

eq

uip

me

nt.

Go

od

- d

red

gin

g

eq

uip

me

nt

an

d

mo

bili

satio

n c

ost

s w

ill b

e lo

we

r th

an

fo

r hyd

rau

lic

dre

dg

ing

, ho

we

ver,

me

tho

d is

less

e

ffic

ien

t a

nd

will

as

a re

sult

be

slo

we

r.

Mo

de

rate

– m

ate

rial

will

re

-su

spe

nd

an

d

mo

ve o

ver t

ime

–

resu

ltin

g in

ch

an

ne

l in

fill a

nd

bu

ild u

p o

f sh

oa

ls.

Go

od

– n

o m

ajo

r o

bst

ac

les

are

e

xpe

cte

d in

o

bta

inin

g a

pp

rova

l.

Ex

ca

vato

r

Lan

d d

isp

osa

l (e

.g. o

n

ne

arb

y va

ca

nt

lot)

/sa

le.

Low

– im

pa

cts

on

th

e

en

viro

nm

en

t o

f K

illic

k C

ree

k w

ill b

e li

mite

d t

o

dre

dg

ing

ac

tivity

on

ly.

Ma

na

ge

me

nt

of

PA

SS

will

be

req

uire

d.

Go

od

– a

cc

ess

an

d

site

co

nst

rain

ts s

ho

uld

n

ot

po

se a

pro

ble

m t

o

the

use

of

lan

d b

ase

d

exc

ava

tors

. A n

ea

rby

lan

d s

tag

ing

site

will

b

e re

qu

ired

–

po

ten

tial t

he

De

pt.

of

Lan

ds

site

on

th

e

we

ste

rn s

ho

re o

f th

e

cre

ek

co

uld

be

an

o

ptio

n.

Exc

elle

nt,

p

art

icu

larly

if s

ale

o

f m

ate

rial i

s p

oss

ible

.

Exc

elle

nt

– p

erm

an

en

t re

mo

val

of

exi

stin

g s

ed

ime

nts

w

ill im

pro

ve

hyd

rod

yna

mic

s a

nd

p

rovi

de

s a

lon

ge

r te

rm s

olu

tion

to

c

urr

en

t se

dim

en

tatio

n

pro

ble

ms.

Mo

de

rate

– f

urt

he

r a

sse

ssm

en

t w

ill b

e

ne

ce

ssa

ry,

pa

rtic

ula

rly re

late

d

to e

xtra

ctiv

e

ind

ust

ry re

gu

latio

ns.

En

viro

nm

en

tal I

nve

stig

atio

n a

nd

Ass

ess

me

nt –

Kill

ick

Cre

ek

Stra

teg

y H

(N

ove

mb

er 2

008)

Eco

Lo

gic

al A

ustra

lia P

ty L

td

5

6

Eco

log

ica

l Ass

ess

me

nt,

GIS

, En

viro

nme

nta

l Ma

na

ge

me

nt a

nd

Pla

nnin

g

Dre

dg

ing

m

eth

od

D

isp

osa

l Site

O

ptio

n En

viro

nmen

tal

Imp

ac

ts

Op

era

tiona

l Fe

asi

bili

ty

Cos

ts

A

chi

eve

men

t of

Stra

teg

y H

Ob

jec

tive

s A

pp

rova

l lik

elih

oo

d

Ae

rial d

isp

osa

l M

od

era

te –

ve

ge

tatio

n

at

ae

rial s

ite is

po

or

co

nd

itio

n E

EC; P

ASS

will

re

qu

ire m

an

ag

em

en

t.

Mo

de

rate

– d

ep

th o

f w

ate

r ma

y b

e a

lim

itin

g f

ac

tor.

A

co

mb

ina

tion

of

exc

ava

tor a

nd

su

ctio

n

dre

dg

ing

ma

y p

rovi

de

a

fe

asi

ble

so

lutio

n.

Ac

ce

ss u

sin

g a

cra

ne

fr

om

th

e w

est

ern

sh

ore

o

f th

e c

ree

k w

ou

ld

ap

pe

ar p

rac

tica

l.

Mo

de

rate

– s

uc

tion

d

red

gin

g w

ill b

e

time

eff

icie

nt

an

d

ma

y o

vera

ll p

rove

fe

asi

ble

. Pip

ing

of

ma

teria

l to

th

e

dis

po

sal s

ite w

ill

avo

id t

he

ne

ed

fo

r a

dd

itio

na

l e

qu

ipm

en

t a

nd

lim

it im

pa

cts

.

Go

od

– t

he

ne

ar

sho

re lo

ca

tion

of

the

d

isp

osa

l site

will

like

ly

resu

lt in

win

d a

nd

tid

e a

ctio

n re

turn

ing

so

me

of

the

ma

teria

l to

th

e c

ree

k sy

ste

m

ove

r tim

e.

Go

od

– n

o m

ajo

r o

bst

ac

les

are

e

xpe

cte

d in

o

bta

inin

g a

pp

rova

l.

Aq

ue

ou

s d

isp

osa

l Lo

w –

imp

ac

ts li

mite

d t

o

ba

re s

an

dy

sub

stra

te

an

d p

oo

r q

ua

lity

ma

ng

rove

are

as.

Mo

de

rate

– d

ep

th o

f w

ate

r ma

y b

e a

lim

itin

g f

ac

tor.

A

co

mb

ina

tion

of

exc

ava

tor a

nd

su

ctio

n

dre

dg

ing

ma

y p

rovi

de

a

fe

asi

ble

so

lutio

n.

Ac

ce

ss u

sin

g a

cra

ne

fr

om

th

e w

est

ern

sh

ore

o

f th

e c

ree

k w

ou

ld

ap

pe

ar p

rac

tica

l.

Mo

de

rate

– s

uc

tion

d

red

gin

g w

ill b

e

time

eff

icie

nt

an

d

ma

y o

vera

ll p

rove

fe

asi

ble

. Pip

ing

of

ma

teria

l to

th

e

dis

po

sal s

ite w

ill

avo

id t

he

ne

ed

fo

r a

dd

itio

na

l e

qu

ipm

en

t a

nd

lim

it im

pa

cts

.

Mo

de

rate

– m

ate

rial

will

re

-su

spe

nd

an

d

mo

ve o

ver t

ime

, re

-e

nte

ring

th

e c

ree

k sy

ste

m a

nd

resu

ltin

g

in b

uild

up

of

sho

als

.

Go

od

– n

o m

ajo

r o

bst

ac

les

are

e

xpe

cte

d in

o

bta

inin

g a

pp

rova

l.

Lan

d

dis

po

sal/

sale

. Lo

w –

imp

ac

ts o

n t

he

e

nvi

ron

me

nt

of

Kill

ick

Cre

ek

will

be

lim

ited

to

d

red

gin

g a

ctiv

ity o

nly

. M

an

ag

em

en

t o

f P

ASS

w

ill b

e a

n is

sue

.

Mo

de

rate

– d

ep

th o

f w

ate

r ma

y b

e a

lim

itin

g f

ac

tor.

A

co

mb

ina

tion

of

exc

ava

tor a

nd

su

ctio

n

dre

dg

ing

ma

y p

rovi

de

a

fe

asi

ble

so

lutio

n.

Ac

ce

ss u

sin

g a

cra

ne

fr

om

th

e w

est

ern

sh

ore

o

f th

e c

ree

k w

ou

ld

ap

pe

ar p

rac

tica

l.

Exc

elle

nt,

p

art

icu

larly

if s

ale

o

f m

ate

rial i

s p

oss

ible

.

Exc

elle

nt

– p

erm

an

en

t re

mo

val

of

exi

stin

g s

ed

ime

nts

w

ill im

pro

ve

hyd

rod

yna

mic

s a

nd

p

rovi

de

s a

lon

ge

r te

rm s

olu

tion

to

c

urr

en

t se

dim

en

tatio

n

pro

ble

ms.

Mo

de

rate

– f

urt

he

r a

na

lysi

s a

nd

a

pp

rova

l re

qu

irem

en

ts w

ill b

e

ne

ce

ssa

ry,

pa

rtic

ula

rly re

late

d

to e

xtra

ctiv

e

ind

ust

ry re

gu

latio

n.

H

ydra

ulic

Be

ac

h

no

uris

hm

en

t.

Low

– im

pa

cts

on

th

e

en

viro

nm

en

t o

f K

illic

k C

ree

k w

ill b

e li

mite

d t

o

Mo

de

rate

– w

ill re

qu

ire

furt

he

r ass

ess

me

nt

(dre

dg

ing

op

era

tor

Mo

de

rate

–

dre

dg

ing

me

tho

d

an

d p

oss

ible

ne

ed

Exc

elle

nt

– sa

nd

will

b

e re

mo

ved

fro

m

rive

r sys

tem

an

d

Mo

de

rate

– w

ill

de

pe

nd

on

imp

ac

ts

to b

ea

ch

an

d d

un

e

En

viro

nm

en

tal I

nve

stig

atio

n a

nd

Ass

ess

me

nt –

Kill

ick

Cre

ek

Stra

teg

y H

(N

ove

mb

er 2

008)

Eco

Lo

gic

al A

ustra

lia P

ty L

td

5

7

Eco

log

ica

l Ass

ess

me

nt,

GIS

, En

viro

nme

nta

l Ma

na

ge

me

nt a

nd

Pla

nnin

g

Dre

dg

ing

m

eth

od

D

isp

osa

l Site

O

ptio

n En

viro

nmen

tal

Imp

ac

ts

Op

era

tiona

l Fe

asi

bili

ty

Cos

ts

A

chi

eve

men

t of

Stra

teg

y H

Ob

jec

tive

s A

pp

rova

l lik

elih

oo

d

the

dre

dg

ing

ac

tivity

o

nly

. D

isp

osa

l in

th

e

ne

ars

ho

re e

nvi

ron

me

nt

will

als

o e

na

ble

PA

SS t

o

be

ma

na

ge

d e

asi

ly.

Furt

he

r ass

ess

me

nt

of

imp

ac

ts o

n d

un

e s

yste

m

ma

y b

e re

qu

ired

.

an

aly

sis)

. fo

r bo

ost

er p

um

p

will

inc

rea

se c

ost

s.

de

po

site

d b

ac

k in

to

co

ast

al s

yste

m.

syst

em

, no

t a

sse

sse

d a

s p

art

of

this

stu

dy.

Re

turn

of

san

d t

o t

he

co

ast

al

syst

em

will

alig

n

with

Go

vern

me

nt

po

licie

s.



8.1.4 Conclusion

The dredging methods selected at Killick Creek will need to:

• be suitable for the specific site;

• reflect environmental best practise

• be cost effective; and

• meet statutory requirements.

Based on the analysis in Table 5 the preferred dredging and disposal option would be: To use a combination of mechanical and suction dredging with disposal of dredged

material into the near shore ocean beach environment. This option will achieve Strategy H objectives by permanently removing existing sand resulting in longer term

benefits. The feasibility and cost implications of this option will require further assessment – if this option proves unfeasible then the next preferred option would be:

To use mechanical dredging equipment and dispose of the dredged material into the aqueous disposal site within Killick Creek. The aqueous disposal site is preferred as it will have minimal environmental impacts and will allow management of PASS.

This option will however only result in a temporary achievement of Strategy H objectives.

Further consideration of dredging operation methods will be required as part of the detailed investigations for the dredging operations once a particular method has been selected. In selecting a method consideration of costs and social issues may be necessary – these have not been considered in this analysis, rather this analysis based on environmental and logistical feasibility.



9. MONITORING STRATEGY 9.1 Compliance Monitoring

Compliance monitoring involves ensuring all approval conditions are met during the life of the project. This may include:

• Recording the amount of sediment dredged;

• Recording the amount of sediment dumped;

• In the event of more than one spoil ground, recording the amount of sediment dumped at each site;

• Adherence with environmental management plans; and/or

• Reporting of environmental incidents.

All of the above compliance monitoring actions are likely to be required for the Killick Creek Sediment Management Program. Details of these actions and additional requirements may be necessary, depending on the outcome of approvals/permitting and the associated consent conditions.

9.2 Impact Monitoring

The aim of impact monitoring is to determine the robustness and longevity of implementing Strategy H. Monitoring should be undertaken immediately after the sediment removal program to obtain baseline data and then at regular intervals to determine the long-term effects of the works. The two specific aims of the monitoring program should be:

1. To determine the success of Strategy H in achieving the stated goal of maintaining the tidal and flood hydrodynamic conditions that have characterised the estuary for the past 30 – 50 years.

2. To assess any associated impacts/benefits of implementing Strategy H e.g. improved water quality, improved ecosystem condition.

ELA has outlined below a suggested monitoring program, which will address the above aims (Table 6). The majority of tasks can be implemented by staff of Kempsey Shire Council, with limited need to engage specialists (e.g. for bathymetric survey, quantitative flora and fauna surveys). The exact location of permanent monitoring sites should be determined once the final options for spoil disposal have been decided. However, factors to consider when determining monitoring locations should include:

• ease of repeated access • ease and cost of installation • location relative to predicted sediment accumulation and erosion • potential hazard to creek users e.g. navigational hazard.

Indicative locations for permanent monitoring sites are provided in Figure 11 following Table 6.

En

viro

nm

en

tal I

nve

stig

atio

n a

nd

Ass

ess

me

nt –

Kill

ick

Cre

ek

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teg

y H

(N

ove

mb

er 2

008)

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ty L

td

6

0

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ironm

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ge

me

nt a

nd

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nni

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Tab

le 6

: Sug

ges

ted

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st-d

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g m

oni

torin

g s

trate

gy

for K

illic

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ess

me

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- Se

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g p

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s w

ithin

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ick

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ek

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ter l

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ls

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am

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, th

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n a

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ark

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(e

.g. s

take

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om

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er t

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ime

nt

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er

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dg

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, th

en

q

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-a

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ick

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ime

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in t

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ithin

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n a

eria

l p

ho

tog

rap

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be

co

me

ava

ilab

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will

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ild o

n t

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c

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t lo

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rm

ph

oto

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of

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n

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(KSC

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(N

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er 2

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tric

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cis

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ath

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of

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dia

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ou

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of

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in re

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r in

un

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in K

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- W

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n a

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ho

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hs

be

co

me

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ilab

le.

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will

bu

ild o

n t

he

c

urr

en

t lo

ng

-te

rm

ph

oto

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ph

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rec

ord

of

the

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ek

cu

rre

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m

ain

tain

ed

by

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n

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ey

(KSC

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nc

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En

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nd

Ass

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me

nt –

Kill

ick

Cre

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Stra

teg

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(N

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Eco

Lo

gic

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ustra

lia P

ty L

td

6

2

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log

ica

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me

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, Env

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ana

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me

nt a

nd

Pla

nni

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one

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eth

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hat t

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Fr

eq

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al

ass

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- C

on

tinu

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ge

of

Kill

ick

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by

fish

a

nd

bird

s fo

r ha

bita

t a

nd

fo

rag

ing

. -

Co

lon

isa

tion

an

d

exp

an

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n o

f se

ag

rass

b

ed

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- R

ec

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/or

rec

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t o

f m

an

gro

ves.

-

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an

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n o

f sa

ltma

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c

om

mu

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-

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er g

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l o

bse

rva

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s.

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me

dia

tely

aft

er

dre

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ing

, th

en

re

gu

larly

th

ere

aft

er.

- M

ay

be

un

de

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o

n a

n a

d-h

oc

ba

sis.

-

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co

rds

of

ob

serv

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ns

sho

uld

b

e k

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nc

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o

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ort

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ity

to in

volv

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up

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an

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ph

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ph

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sta

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s

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pa

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c

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tatio

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mm

un

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s e

.g.

saltm

ars

h, m

an

gro

ve,

sea

gra

ss, i

nva

sive

sp

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ies

(e.g

. Bito

u

bu

sh).

- Im

me

dia

tely

aft

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dre

dg

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, th

en

q

ua

rte

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o 6

-m

on

tly t

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rea

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nc

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Fl

ora

and

Fa

una

En

sure

th

at

dre

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s n

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ne

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ac

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on

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a.

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ny

lon

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be

ne

fits

of

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to

flo

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un

a.

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ntif

ic s

urv

ey

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f b

en

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d d

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tes.

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alit

ativ

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/fis

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eta

tion

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om

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me

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tely

aft

er

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dg

ing

, th

en

q

ua

rte

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o 6

-m

on

tly t

he

rea

fte

r.

Exp

ert

En

viro

nm

en

tal I

nve

stig

atio

n a

nd

Ass

ess

me

nt –

Kill

ick

Cre

ek

Stra

teg

y H

(N

ove

mb

er 2

008)

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Lo

gic

al A

ustra

lia P

ty L

td

6

3

Eco

log

ica

l Ass

ess

me

nt,

GIS

, Env

ironm

ent

al M

ana

ge

me

nt a

nd

Pla

nni

ng

Mo

nito

ring

Co

mp

one

nt

Aim

M

eth

od

W

hat t

o M

ea

sure

Fr

eq

uenc

y W

ho

Sed

ime

nt

test

ing

-

Sed

ime

nt

co

nta

min

an

t le

vels

–

sho

uld

no

t b

e h

igh

er

tha

n p

re-d

red

gin

g

surv

ey.

-

PA

SS –

rele

ase

an

d

spre

ad

th

rou

gh

ou

t K

illic

k C

ree

k.

- Im

me

dia

tely

aft

er

dre

dg

ing

Exp

ert

W

ate

r and

se

dim

ent

qua

lity

En

sure

th

at

dre

dg

ing

ha

s n

o

ne

ga

tive

imp

ac

ts

on

wa

ter/

sed

ime

nt

qu

alit

y th

rou

gh

th

e

rele

ase

of

co

nta

min

an

ts.

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term

ine

an

y lo

ng

-te

rm b

en

efit

s o

f d

red

gin

g t

o

wa

ter q

ua

lity.

Wa

ter q

ua

lity

test

ing

-

Wa

ter

qu

alit

y p

ara

me

ters

p

art

icu

larly

DO

.

- In

co

rpo

rate

d in

to

Co

un

cil’

s c

urr

en

t w

ate

r qu

alit

y te

stin

g

with

in t

he

low

er

rea

ch

of

the

Kill

ick

Cre

ek.

C

ou

nc

il



Figure 11: Indicative location of monitoring sites



10. SUMMARY AND CONCLUSIONS The purpose of this study was to conduct an environmental investigation and assessment of Strategy H of the Killick Creek Estuary Management Plan. Specifically, this study has implemented the first two actions of Strategy H, which were to conduct an up-to-date hydrographic survey of Killick Creek and to prepare a detailed environmental impact assessment of the proposed works (including a sediment study). Further to these actions, and included in this study, were analysis of the relevant approvals and dredging options. A monitoring strategy was also proposed. The major conclusions and recommendations of this report are listed below.

1. The bathymetry of Killick Creek has changed markedly between 2001 and 2008, with a significant accumulation of sediment in the lower reaches of the creek. A new bathymetric survey is recommended post-dredging to confirm the altered creek depths.

2. Sediments of Kilick Creek are predominantly coarse, grey sand and are not

contaminated. Potential acid sulfate soils (PASS) are present at some locations within the proposed dredging location. Consequently, aqueous disposal of dredge spoil is recommended and further investigations into the extent of PASS will be required should dredging deeper than 0.5 metres be required.

3. Consultation with relevant government agencies and stakeholders was

undertaken. No agency opposed the action provided certain conditions are met (Table 1 and Appendix 3).

4. An analysis of relevant legislation and planning instruments was undertaken. It

was concluded that the proposed dredging can be assessed and approved under Part 5 of the EP&A Act.

5. A section 200 permit will also be required under the Fisheries Management Act

and Council will need to seek concurrence for the action from the Minister for Environment and Climate Change to fulfil the requirements of the Coastal Protection Act.

6. Additionally, any blockages to fish passage within watercourses as part of the

works will also require a permit under Section 219 of the FM Act. The FM Act, through the Fish Habitat Protection Plan No.1, also requires public authorities, including local government and State authorities to notify the Minister of any Proposal to remove or relocate woody debris.

7. Should a sand extraction option be preferred, additional approvals

requirements will apply pursuant to the EP&A Act, FM Act and POEO Act (refer 6.5).

8. A detailed environmental impact assessment was undertaken to assess the

likely impacts of the proposed dredging on Killick Creek flora and fauna. Environmental impacts of the proposed dredging are likely to be short-lived and limited in spatial extent, provided PASS are not exposed. It is therefore recommended that dredge spoil should be dumped at an aqueous and not



an aerial disposal location. No significant impacts are anticipated on threatened species or any other matter of National Environmental Significance (NES).

9. The dredging method most effective in achieving long-term success of

Strategy H is removal of sediment from Killick Creek and disposal of dredged material into the near shore ocean beach environment. This option will require additional assessment. The next preferred option is to use mechanical dredging equipment and dispose of the dredged material into the aqueous disposal site within Killick Creek.

10. Council must consider the ongoing management and monitoring of the works

with regards to the local and regional environment. Monitoring would include preparation of a Construction Environmental Management Plan to ensure the construction works do not impact the creek and surrounds. Details of a longer-term monitoring program have been developed (Table 6).



11. REFERENCES

Beach Protection Authority (2008) Descriptions of major Sand Dune Plants: Sand Spinifex Grass, Leaflet No. IV-01 [Available] http://www.epa.qld.gov.au/publications/p00278aa.pdf/Sand_spinifex_grass_iSpinifex_sericeus/i.pdf Accessed 28/07/08. NSW Department of Primary Industry (DPI) (2008) Estuarine Habitats – Fact Sheet [Available] http://www.dpi.nsw.gov.au/fisheries/habitat/aquatic-habitats/estuarine Accessed 28/07/08. Manly Hydraulics Laboratory (2002) Killick Creek Estuary Processes Study, Report to Kempsey Council, Report No. MHL1125. UNE (1993) Report on Killick Creek, NSW – Biological and Hydrological Status of the Creek, Causes and Recommendations Regarding Oxygen Depletion. Prepared for Kempsey Council by the Dept of Zoology, University of New England and the Centre for Coastal Research, Southern Cross University. WBM Oceanics Australia (2006) Killick Creek Estuary Management Study and Plan, Report to Kempsey Council West RJ, Thorogood CA, Walford TR and Williams RJ (1985) An Estuarine Inventory for NSW, Australia. Division of Fisheries, NSW Dept of Agriculture, Sydney.



APPENDICES

Environmental Investigation and Assessment – Killick Creek Strategy H (September 2008)

Eco Logical Australia Pty Ltd Ecological Assessment, GIS, Environmental Management and Planning

Appendix 1 – Bathymetric Survey

Hydrographic & Cadastral Survey Pty LtdA.B.N 90 116 658 416

Web: www.hcsurvey.com.auPO Box 171, Figtree , NSW 2525. Email: [email protected]

Phone: 1300 796 956 Mob: 0431 209 080 Fax: (02) 4227 2407

COMMERCIAL – IN – CONFIDENCEPage 1 of 2

19 May 2008

Eco Logical Australia Pty LtdGPO Box 1558CANBERRAACT 2601Australia

Attention: Mr Tom Kaveney

SURVEY REPORT – KELLICK CREEK HYDROGRAPHIC SURVEY

References:A. Quotation – Hydrographic & Cadastral Survey, 14 Mar 08B. Email – Eco Logical Australia, Killick Creek hydro data dated 07 May 08

Dear Sir

1. Hydrographic survey activities as revised, were conducted on 16 and 17 May 08 andincluded both wading and boatwork. The adjustment to survey activities included the reduction ofarea limited to Sheet 4 as previously provided and to contain the activity within a two day surveywindow. Field work was conducted from 0600 to 1730 on both days followed by survey datareduction.

2. Further examination of the original x,y,z file provided at Reference B confirmed the datasetto be on the Australian Map Grid (AMG) as per the plan sheets. The quotation was for data to berendered in Map Grid Australia (MGA) which for the purpose of modern engineering andenvironmental projects allows everyday use of the Global Positioning System (GPS). A convertedx,y,z of the original file has been provided for use in comparison work and Digital TerrainModelling against the new MGA dataset.

3. Data was acquired using robotic total station, real time kinematic GPS and Ceeducer Proechosounder. State survey marks used for control included PM12883 and PM12668. Additionalstations were established along the creek and shoreline for line of sight observations.

4. Original supplied data was reduced to Australian Height Datum (AHD). This datumequates to Mean Sea Level (MSL) and is not the normal reduction datum when relating to theavailable minimum depth of water. This datum would be Lowest Astronomical Tide (LAT). It isstill possible to reduce both datasets to LAT which would provide a better relationship to theminimum amount of water expected in the creek, shore line and offshore. By knowing waterdepth relative to LAT, a better estimate of the sedimentation removal requirement can becalculated for the area if this is an intended outcome.

COMMERCIAL – IN – CONFIDENCE

Hydrographic & Cadastral Survey Pty LtdA.B.N 90 116 658 416

Page 2 of 2

5. Some areas of the creek area were inaccessible due to hazards such as quick sand andunderwater obstructions. These areas are noticeable when conducting comparison with theprevious dataset.

6. Rendered x,y,z files are on UTM Zone 56, CM 153E. Negative values are heights aboveAHD and positive are heights below AHD. The two files are as follows:

a. AMG to MGA Killick Supplied.xyz (original dataset converted)b. Combined_sort_3m_170508.xyz (new dataset, thinned to 3m intervals for high

density observations)

7. Please do not hesitate to contact the undersigned if further information about the area isrequired or you wish to discuss another product that could be derived from the information.

Yours faithfully

Richard CullenSenior Hydrographic ConsultantCertified Professional – Hydrography (Level 1)

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Environmental Investigation and Assessment – Killick Creek Strategy H (September 2008)

Eco Logical Australia Pty Ltd Ecological Assessment, GIS, Environmental Management and Planning

Appendix 2 – Sediment Quality Assessment

Coffey Geotechnics Pty Ltd ABN 93 056 929 483 1/18 Hurley Drive Coffs Harbour NSW 2450 Australia

ESTUARY SEDIMENT QUALITY ASSESSMENT – KILLICK CREEK, CRESCENT HEAD, NSW

Eco Logical Australia Pty Ltd COFFS HARBOUR GEOTCOFH02326AA-AB 22 July 2008

Coffey Geotechnics Pty Ltd ABN 93 056 929 483 GEOTCOFH02326AA-AB 1/18 Hurley Drive Coffs Harbour NSW 2450 Australia PO Box 704 Coffs Harbour 2450 Australia T (+61) (2) 6651 3213 F (+61) (2) 6651 5194 www.coffey.com.au

22 July 2008

Eco Logical Australia Pty Ltd PO Box 484 COFFS HARBOUR NSW 2450

Attention: Simon Williams

RE: Estuary Sediment Quality Assessment, Killick Creek, Crescent Head, NSW

1 INTRODUCTION

1.1 General Coffey Geotechnics Pty Ltd (Coffey Geotechnics) was engaged by Eco Logical Australia Pty Ltd to undertake an Estuary Sediment Quality Assessment (ESQA) for the surface sediments in the lower reaches of Killick Creek, adjacent to and upstream of Crescent Head. The site under investigation had an area of approximately 7500m2.

Kempsey Shire Council (Council) is currently investigating the feasibility of removing sediment shoals (see Photo 1 and 2 below) which have formed in Killick Creek. These sediment shoals are inhibiting adequate tidal flushing of the estuary and restricts flood water discharge.

Coffey Geotechnics understanding is that the proposal being considered by Council is to remove up to approximately 10,000m3 of sediment from Killick Creek by dredging within this investigation area. The removal of the sediment by dredging would restore a deeper channel through the site and assist in improving flushing within this waterway. A site sampling plan (Figure 1) is attached.

The ESQA findings will assist Council’s planning for Killick Creek and assist in applications for dredging permits and approvals required to undertake future dredging works and the removal of sediment from the estuary.

1.2 Scope of Work The objective of the ESQA was to assess if potential contaminants of concern and acid sulfate soils may be present in the sediment shoals in Killick Creek.

The main components of work comprised:

Fieldwork, Coffey Geotechnics inspected and photographed the sediment shoals in Killick Creek and collected surface sediment samples for analysis from 9 locations, see Figure 1. Sediment samples were selected for screening purposes to identify potential contaminants in sediments at Killick Creek.

• Laboratory testing of the sediment samples collected included analyses to grade the sediments, broad screening for potential contaminants of concern and testing for the presence of acid sulfate soils. Sediment samples were analysed for the following suite:

• Sediment grading and hydrometer;

• Metals (Arsenic, Cadmium, Chromium, Copper, Cobalt, Lead, Mercury, Molybdenum, Nickel, Tin, Selenium & Zinc);

• Total petroleum hydrocarbons (TPH);

• Benzene, toluene, ethyl-benzene and xylene (BTEX);

• Polycyclic aromatic hydrocarbons (PAH);

• Organochlorine pesticides (OCP);

• Organophosphorus pesticides (OPP);

• Total nitrogen (TN);

• Total phosphorus (TP);

• Field screening tests for acid sulfate soils; and

• Testing of a subset (5 samples) using the Chromium reduction (full QASSIT/ASSMAC) suite for acid sulfate soils.

• Reporting, Coffey Geotechnics has prepared this letter report which presents the findings of the ESQA and compares the laboratory results to current guidelines and adopted criteria.

Coffey Geotechnics work was carried out with reference to the following guidelines:

• DEC Guidelines for the NSW Site Auditor Scheme (2nd ed), 2006;

• ANZECC Australian and New Zealand Guidelines for Fresh and Marine Water Quality,2000;

• DUAP EPA Managing Land Contamination Planning Guidelines, SEPP 55 – Remediation of Land, 1998;

• NSW EPA Guidelines for Consultants Reporting on Contaminated Sites, 1997;

• NSW EPA Sampling Design Guidelines, 1995; and

• NSW EPA Guidelines for Assessing Service Station Sites, 1994.

2 BACKGROUND INFORMATION

2.1 Site Description Coffey Geotechnics Environmental Scientists visited the site within Killick Creek on the morning (at low tide) of the 11 June 2008 to inspect the shoals and collect sediment samples for analysis.

Killick Creek is a small tidal coastal estuary on the Mid North Coast, situated adjacent to the Crescent Head Township. The estuary is an intermittent coastal lagoon connected to the ocean. The Killick Creek estuary is an important part of the Macleay River Flood Mitigation Scheme.

A small body of water was present on the southern bank of the creek during fieldwork which was timed to coincide with a low tide of 0.52m at 8:42am. The depth of water within the investigation area was about 0.3m deep and 8m wide, see photo 1 below. Upstream of the junction with Muddy Arm the depth of the creek increased up to an estimated 1.0m, see Photo 2 below.

Photo 1 – Killick Creek at low tide looking upstream. Photo shows a small body of water confined to a narrow channel along the revetment wall on the southern bank of the creek.

The site is bound by coastal heath to the north and west on the shores of the estuary. Residential allotments were located to the south east of the site and a rock revetment wall on the southern bank of the creek. The rock wall extends from the mouth upstream to the junction with Muddy Arm in the north of the site, see photo 2 below. The investigation area was located approximately 250m upstream of the entrance of Killick Creek to the Pacific Ocean.

Photo 2 – Killick Creek estuary at the junction with Muddy Arm. Photos shows the extensive sediment shoals found in the centre of the investigation area and the deeper water found in the north of the site (right of photo).

2.2 Topography and Geology Regionally the site is situated within an area of moderately sloping topography. Locally, the investigation area was confined to the tidal flats within Killick Creek. The 1:250,000 scale geological map of Hastings indicates that the site locality is underlain by Quartzose sand and silt.

Reference to the Kundabung 1:25,000 Acid Sulfate Soil map indicates that the site of the proposed dredging consists of estuarine sediments with a high probability of acid sulfate soils to occur in sub-surface sediments.

3 FIELD INVESTIGATION Fieldwork was carried out on 11 June 2008 by Coffey Geotechnics Environmental Scientists. Samples were collected from the surface to a depth of 0.5m using a modified length of 50mm diameter PVC piping with an attached screw in cap to seal and retain the collected sample. This sampling method provided an undisturbed profile of surface sediments in the samples collected from Killick Creek. Sampling equipment was washed between each sample location by brush scrubbing with phosphate free detergent (Decon 90) and rinsed with potable water.

Each sediment sample collected for contamination assessment was placed in a clean 250ml glass jar supplied by the laboratory. The acid sulfate soil and sediment grading samples were bagged in plastic bags and sealed with a rubber band. A new pair disposable nitrile gloves was used at each sample location.

Samples were stored in a chilled insulated container during fieldwork and transport to the laboratory. One duplicate sample for contamination assessment was collected during fieldwork for quality control purposes.

4 SITE CONTAMINATION ASSESSMENT

4.1 Sediment Investigation Levels (SILs)

In order to assess the potential contamination in sediments within the investigation area, the results of sediment analyses were compared with guidelines in the following references:

• NSW DEC Guidelines for the NSW Site Auditor Scheme (2nd ed), 2006;

• ANZECC (2000) Australian and New Zealand Guidelines for Fresh and Marine Water Quality, 2000; and

• NSW EPA Guidelines for Assessing Service Station Sites, 1994.

In NSW the ANZECC (2000) are the primary guideline used in the assessment of sediment quality characteristics in waterways, in particular the recommended sediment quality guidelines provided in Table 3.5.1 which is divided into interim sediment quality guideline (ISQG) low (trigger value) and high values. The ISQG-Low (trigger value) is referred to in Table 1 and where appropriate has been adopted as the SIL.

The ANZECC (2000) guidelines provide recommended values for a range of metals, metalloids, organometallic and organic sediment contaminants. ANZECC (2000) states that there are no specific guidelines values provided in available literature for ammonia or nutrients such as phosphate and nitrate.

The NSW DEC (2006) Guidelines for the NSW Site Auditor Scheme summarises the National Environmental Health Forum (NEHF) investigation levels1 for protection of human health for different land uses for a range of contaminants in soils.

The NSW EPA (1994) guidelines provide acceptable cleanup levels at service station sites that are to be redeveloped for a sensitive use such as residential. The NSW EPA also recommends the use of these guidelines for assessing hydrocarbon contaminants for sites with less sensitive land uses.

The DEC (2006) and EPA (1994) guidelines are included for information purposes and may become relevant if it is proposed that sediment extracted from the Killick Creek estuary be used in other land based development. These guideline values are used in assessing levels of contaminants of concern for residential use.

Where appropriate the investigation levels specified in NSW DEC (2006) and NSW EPA (1994) guidelines have been adopted.

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�Table 1: Sediment Investigation Levels (SILs) adopted – note units vary between mg/kg or µg/kg dependent on class of contaminants

Contaminants of Concern

NSW DEC 20062

NSW EPA 1994

ANZECC ISQG – Low

(Trigger value)

SIL Adopted

Heavy Metals (mg/kg)

Arsenic 100 - 20 20

Cadmium 20 - 1.5 1.5

Chromium (Total) 100 - 80 80

Cobalt 100 - 100

Copper 1000 - 65 65

Lead 300 300 50 50

Mercury 15 - 0.15 0.15

Nickel 600 - 21 21

Zinc 7000 - 200 200

Polycyclic Aromatic Hydrocarbons (µg/kg)

Acenaphthene - - 16 16

Acenaphthalene - - 44 44

Anthracene - - 85 85

Benz(a)anthracene - - 261 261

Benzo(a)pyrene 1,000 - 430 430

Chrysene - - 384 384

Dibenz(a.h)anthracene - - 63 63

Fluoranthene - - 600 600

Fluorene - - 19 19

Naphthalene - - 160 160

Phenanthrene - - 240 240

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Contaminants of Concern

NSW DEC 20062

NSW EPA 1994

ANZECC ISQG – Low

(Trigger value)

SIL Adopted

Pyrene - - 665 665

Total PAH 20,000 - 4000 4000

BTEX (mg/kg)

Benzene - 1 - 1

Toluene - 1.4 - 1.4

Ethyl Benzene - 3.1 - 3.1

Xylenes Total - 14 - 14

Total Recoverable Hydrocarbons (mg/kg)

C6 – C9 - 65 - 65

C10 – C24 - - - -

C15 – C36 - - - -

C29 – C36 - - - -

C10 – C36 (Total) - 1000 - 1000

Organochlorine Pesticides (µg/kg)

Aldrin + dieldrin 10,000 - - 10,000

Dieldrin - - 0.02 0.02

Chlordane 50,000 - 0.5 0.5

Endrin - - 0.02 0.02

Lindane - - 0.32 0.32

DDT + DDD + DDE 200,000 - - 200,000

Total DDT - - 1.6 1.6

p.p’-DDE - - 2.2 2.2

o,p’-+p,p’-DDD - - 2 2

Heptachlor 10,000 - - 10,000

4.2 Quality Assurance (QA)/Quality Control (QC)

Samples were transported under chain of custody conditions and in chilled insulated containers to MGT Environmental Consulting Pty Ltd (MGT) NATA accredited Melbourne laboratory, sediment gradings

were analysed by Coffey Geotechnics Coffs Harbour laboratory and the acid sulfate soils were analysed by Biotrack’s Brisbane laboratory. A copy of the chain of custody is included with the laboratory test results in Appendix A.

MGT laboratory conducted internal quality control using laboratory duplicates, spikes and method blanks. The results are shown with laboratory test results in Appendix A. Analytical methods used for the laboratory testing are also indicated on the laboratory report sheets. The results of laboratory quality control testing are considered to be within acceptable limits.

For QA/QC purposes one duplicate sample (SS01) was submitted for analysis. The duplicate sediment sample collected during field work was analysed for TRH, BTEX, heavy metals and OCP/OPP, total nitrogen and total phosphorus. Results of QA/QC testing are summarised in Table 2.

The comparison of the test results for the primary and field duplicate sample indicates that the RPDs for arsenic, total nitrogen and total phosphorus in each sample were below the control limit. Other parameters analysed were below their respective laboratory limit of reporting (LOR), and it was not possible to calculate an RPD for these anolytes.

Based on the above assessment it is considered that the field and laboratory methods are appropriate and that the data obtained is usable and considered to represent the concentrations at the sampling points at the time of sampling.

4.3 Comparison of Results to Sediment Investigation Levels

The laboratory test results for the sediment sampling on the 11 June 2008 are present in Appendix A and summarised in Table 3 attached to this report.

The material properties of three sediment samples were tested by Coffey Geotechnics by grading and hydrometer and the test results are presented in Appendix A. The results for all three samples were very similar and that the sediment can be described as coarse grey sand as the majority of material had a grain size between 300µm and 150µm.

The results of the laboratory testing show that potential contaminants of concern were all below the adopted sediment investigation levels. The following points are noted from Table 3:

• Concentrations of heavy metals were recorded below the adopted investigation levels in each sample analysed;

• Concentrations of BTEX and TRH were recorded below the adopted investigation levels and laboratory’s LOR in each sample analysed;

• Concentrations of PAH, OCP and OPP were recorded below the laboratory’s LOR in each sample analysed. For some analytes the laboratories LOR was greater than the adopted investigation level which was derived from the ANZECC (2000) low trigger values;

• No SIL was adopted for total nitrogen. Concentrations of total nitrogen ranged from a minimum of 31 mg/kg at SS01 to a maximum of 120 mg/kg at SS08, and

• No SIL was adopted for total phosphorus. Concentrations of total phosphorus ranged from a minimum of 31 mg/kg at SS08 to a maximum of 81 mg/kg at SS03.

5 ACID SULFATE SOILS 5.1 Formation and Potential Impacts

Acid Sulfate Soils (ASS) are soils which contain significant concentrations of pyrite which, when exposed to oxygen, in the presence of sufficient moisture, oxidises, resulting in the generation of sulfuric acid. Unoxidised pyritic soils are referred to as potential ASS (PASS). When the soils are exposed, the oxidation of pyrite occurs and sulfuric acids are generated, the soils are said to be actual ASS (AASS).

Pyritic soils typically form in waterlogged, saline sediments rich in iron and sulfate. Typical environments for the formation of these soils include tidal flats, salt marshes and mangrove swamps below about RL 5m AHD. They can also form as bottom sediments in coastal rives and creeks.

Pyritic soils of concern on low lying NSW and coastal lands have mostly formed in the Holocene period, (i.e. 10,000 years ago to present day) predominantly in the 7,000 years since the last rise in sea level. It is generally considered that pyritic soils which formed prior to the Holocene period would already have oxidised and leached during periods of low sea level which occurred during ice ages, exposing pyritic coastal sediments to oxygen.

Disturbance or poorly managed development and use of acid sulfate soils can generate significant amounts of sulfuric acid, which can lower soil and water pH to extreme levels (generally pH <4) and produce acid and salts, resulting in high salinity.

The low pH, high salinity soils can reduce or altogether preclude vegetation growth and can produce aggressive soil conditions which may be detrimental to concrete and steel components of structures, foundations, pipelines and other engineering works.

Generation of the acid conditions often releases aluminium, iron and other naturally occurring elements from the otherwise stable soil matrices. High concentrations of such elements, coupled with low pH and alterations to salinity can be detrimental to aquatic life. In severe cases, affected waters flowing off-site can have detrimental effect on aquatic ecosystems

5.2 Acid Sulfate Soils Risk Map

The Department of Land and Water Conservation 1 Kundabung 1:25,000 Acid Sulfate Soil map indicates that the site of the proposed dredging consists of estuarine sediments with a high probability of acid sulfate soils to occur in sub-surface sediments.

5.3 Laboratory Testing

Sediment samples collected for acid sulfate soils analysis were sent to Biotrack Brisbane laboratory for testing. Initially 10 sediment samples from the 9 sampling locations were field screened to assess potential rate of pH change and to select a subset of five samples selected for Chromium Reducible Sulfur tests (CRS) to assess the potential for acid generation. The results of this testing are presented in Appendix A and are summarised in Table 4.

The following points are noted from Table 4:

• Samples AS08 and AS10 reported concentrations of reduced inorganic sulfur (%SCr) greater than the action criteria of 0.03%. The result provides a direct measure of sulfides present and results above the action criteria of >0.03% flag an of concern soil;

• Samples AS07 and AS10 reported concentrations of equivalent sulfur greater than the action criteria of 0.03%. This measure is the sum of the acid forming factors less the acid neutralising factors. Soils with %SEQ values which exceed the action criteria of >0.03% indicate that the soil is an acid sulfate soil requiring management.

The test results confirm that acid sulfate soils are present within the investigation area in Killick Creek, however, it is noted that not all of the samples collected exceeded the action criteria. The finding suggests that acid sulfate soils may occur as hotspots within the investigation area.

The test results also show that there is sufficient carbonate in the sediments, for example carbonate can be in the form of marine shell fragments, to be self neutralising for these soils. The concentration of MgKCL in all five samples was greater than the action criteria, >100mg/kg and the corresponding alkaline pHKCL are indicators of the presence of carbonates. The suggested liming rates to neutralise these soils are also low at <5kg/m3.

At present no active management of the acid sulfate soils within these sediments is necessary provided they were to remain undisturbed.

A limitation of this initial investigation was that the sediment samples were collected from the surface to a depth of 500mm from the shoals in Killick Creek. If disturbance of these sediment shoals is proposed then further investigation of acid sulfate soil potential of sediments at greater depths than 500mm is recommended prior to commencement of works.

6 CONCLUSIONS AND RECOMMENDATIONS Coffey Geotechnics investigation of surface sediments in Killick Creek found no evidence of significant contamination from contaminants of concern within the investigation area. The results of laboratory testing of nine sediment samples collected in a transect along Killick Creek found that level of contaminants of concern were less than adopted Sediment Investigation Levels or were below the laboratories limits of reporting (LOR).

For some analytes within classes of poly aromatic hydrocarbons (PAH), organochlorine pesticides (OCP) and organophosphorus pesticides (OPP) the laboratories LOR was greater than the adopted investigation level which was derived from the ANZECC (2000) low trigger values. It was noted that the ANZECC (2000) low trigger values are at very low concentrations (µg/kg). To confirm if all of the investigation levels were not exceeded would need to be determined with further testing of the sediment samples at trace limits of reporting.

Alternatively, as none of the sediment samples tested returned a reported result greater than the laboratories LOR for PAH, OCP or OPP this finding suggests that these contaminants of concern are unlikely to be present in the Killick Creek surface sediments.

Testing for acid sulfate soils found that these soils do occur within the investigation area with several sample locations reporting the presence of sulfides above action criteria adopted from the NSW ASSMAC (1998) guideline. The test results also confirmed the presence of a high level of carbonates in the sediments which may act as a buffer to these acid sulfate soils. At present no active management of the acid sulfate soils within these sediments is necessary provided they were to remain undisturbed.

Coffey Geotechnics recommends that further investigation to delineate the presence of acid sulfate soils occurs prior to any disturbance of sediments or works within the investigation area in Killick Creek.

ECOLOGICAL IMPACT ASSESSMENT · Eco Logical Australia Pty Ltd 39 Ecological Assessment, GIS,...

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