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Public Information Booklet Question ñ With respect to impact on the coast you indicated 40 hectares of vine thicket would be impacted to the south of James Price Point. How big is the coastal impact overall? The actual area of disturbed coast is dependent on the final location of the site. It has been estimated to be approximately 1.3 to 1.5 kilometres of coastal disturbance. This area includes the shoreline, coastal dunes and up to 40 to 60 hectares of vine thicket (for a southern site). The pipeline corridor may also require some vine thicket clearing, and this will be rehabilitated once the pipeline is installed. Vine thickets occur in many locations along the Dampier Peninsula coastline. The 40-60 hectares represents about 10-15% of the vine thickets that are occur in the James Price Point area. 5.4. Marine Issues Construction (Dredging and Blasting) Question ñ How much dredging is necessary? Preliminary estimates indicate a total dredging volume for a southern James Price Point site to be in the order of 6 to 8 million cubic metres or less than half the volume of the northern site. It is estimated about 10% of this material would need to be blasted to enable removal. Total dredging volume for a northern James Price Point location would be approximately 15 to 20 million cubic metres. Based on the preliminary understanding of the seabed material, about half of this (50%) potentially needs to be blasted to enable removal. This estimated blast volume is about 12 times the required blasting for the southern site. Question - How often will repeat or maintenance dredging be required? Currently there is insufficient information to make an assessment on maintenance dredging requirements. Once a better understanding of seabed properties and the movement of sand in the area is understood from planned studies and sampling programs a scientifically based estimate can be made on the need for repeat or maintenance dredging. However based on professional experience it is anticipated to be around every 5-10 years. Question ñ With respect to dredge sediment, how long will it be until the sediment settles down and how do you intend to control and contain the dredge plume? Once the dredge stops operating the water is typically back to normal within a few hours and usually it isnít possible to measure any plume after 12 to 24 hours. This time is likely to vary based on weather conditions; current flow; type of material being dredged and the dredge technique being used. As part of the environmental impact assessment and engineering design work more information will be collected on the material to be dredged; currents and waves in the area; water depth; and seabed characteristics to better understand what is likely to occur. This then enables the selection of the type of dredging technique that can used and with 5279225 59
Public Information Booklet the support of modelling what needs to be done to control the dredge plume (cloudiness in the water). Questions: � Do any plants and animals die during dredging? � What are the environmental effects of dredging? The key risks to plants and animals from dredging are a result of the generation of sediment plumes (cloudiness in the water) in the area around dredging activities. This sediment plume/cloudiness could cause temporary disturbance to fish, mammals, reptiles etc which could result in these species temporarily moving away from the area. This however would be a temporary behaviour change and once the sediment settles these species would resume normal behaviour patterns. Dredging, which involves removal of sediment form the sea bed, can directly cause loss of sea grass and corals if they are situated on the seabed that is dredged. The environmental impact assessment identifies areas of seagrass, coral, algae etc and the port layout, channel etc are designed to minimise impacts to these habitats. There is also a risk of impact to these marine habitats from the dredge plume in the water generated. Dredge plumes/cloudiness in the water can spread out and potentially smother algae, sea grass etc as the sediment settles. The environmental impact assessment will determined the extent of the dredge plume and predict the likely area of marine habitats potentially impacted. The dredging will then be designed to minimise this impact to an acceptable level. Question ñ What are the likely impacts on reefs? Is this linked to drilling for the jetty? The nearshore marine environment/saltwater country consists of sandy patches and an extensive rocky platform extending from the shore. There are no coral reefs close to the site, although there are some small patches of isolated coral and sparse sea grasses, particularly in the northern area. Construction of the jetty, breakwater and other marine facilities will likely involve piling and dredging in the nearshore marine environment. Depending on the location of the site, the impacts to the marine environment including the rocky platform will include some physical disturbance (e.g. holes drilled into the rocky bottom to stabilise the jetty) and also temporary disturbance from sediments which become stirred up during the process. The Environmental Impact Assessment (EIA) being undertaken by the State in cooperation with Woodside aims to identify the impacts to elements of the environment (including areas of reef, sea grass etc) and development measures to reduce these impacts to acceptable levels. Question - How long until the sea life comes back after dredging? Sediment plumes (cloudiness of the water) caused by dredging temporarily affect water quality in the area around the activities. The higher turbidity of these waters could cause some species to temporarily move away from the area, however these are likely to 5279225 60
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