Assessment of Environmental Impact of STP Discharge to Evans River

DISCHARGE SCENARIO IMPACT RISK ASSESSMENTS 8-19estuary. The magnitude of the predicted increases is largest in the lower estuary and lowest inthe upper estuary.8.6 Social and Environmental Value ImpactsFollowing on from a review of social and environmental values associated with the estuary (refer toSection 3.8); further assessment of the potential impacts of the discharge scenarios on identifiedsocial and environmental values is provided below:• Nature Conservation Values – Minor increases in nutrient concentrations have been predictedthroughout the estuary for ebb-tide and continuous release discharge scenarios (but not forwetland / forest scenario) thereby increasing the risk of a biological or ecosystem response, e.g.changes in macroinvertebrate community abundance and distribution, increased algal productionand associated risk of algal blooms, changes in trophic status of estuary, etc. These outcomes ifrealised could impact on identified nature conservation values and have longer term cumulativeimpacts on the estuary to support certain fish and bird populations. It would be prudent tocomplete further more detailed water quality modelling which can assess these implications. Ifsignificant impacts are identified in this regard, this would influence scheme feasibility.In addition to in-stream nature conservation values, the Evans River catchment itself has avariety of terrestrial flora and fauna values. The siting of the wetland / forest and associatedpipelines to this system or to lower estuarine discharge locations would need to be cognisant ofthese terrestrial values. Further assessments would need to be completed at a later stage in thesiting of this infrastructure depending on the scheme which is ultimately chosen for assessment.• Cultural and Heritage Values – Options leading to a noticeable biological response which affectthe health of the estuary may impact on cultural values and its role in food harvesting. There arelikely to be a number of cultural and heritage significant sites within the catchment which willneed to be considered in planning any pipeline route.• Education and Scientific Values – It is unlikely that the introduction of the STP effluent wouldsignificantly impact on the estuary’s education and/or scientific values. The siting of the wetland /forest and associated drainage infrastructure should be considerate of the location of thesubfossil coral reef and not give rise to direct or indirect impacts on this, i.e. direct damagethrough construction or enhanced bank erosion through poorly designed dischargeinfrastructure.• Scenic Values - It is possible that the bridge and revetment wall discharges (and possibly theentrance site) may on occasions be visible to the public either through the presence of surfaceripples, or via differences in water clarity/hue in the immediate vicinity of the discharge. Theseeffects would only be noticeable under certain conditions, i.e. certain low tides, clear ambientwater surrounding the discharge, etc. While not considered a major impact, these effects maylessen an individual’s appreciation of the estuary’s scenic values.The wetland / forest scheme will be far less evident to the general population and the likely effecton scenic values is considerably reduced.• Recreation and Tourism Values – Assessment completed as part of this investigation have notfocused on faecal contamination of the estuary. Generally, recreational water quality standardsand aquatic food standards relate to the degree of faecal contamination present withinG:\ADMIN\B17607.G.DCC_EVANSRIVER\R.B17607.001.03.REVISED FINAL.DOC