Message
Please refer to the attached file, which is also pasted here.
14 November, 2011
Department of Planning
Major Projects
Sydney 2000
Re: Brooklyn and Dangar Island Sewerage Scheme - Modification to Condition 63
I object to the request by Sydney Water to Modify Condition 63 of the prior approval of the Brooklyn Dangar Sewerage Scheme.
The request should not be considered until Sydney Water (SW) 1. fully considers alternatives to increasing nutrient levels in the effluent being discharged into the Hawkesbury River from the Brooklyn Sewage Treatment Plant (BSTP), 2. models the effects of increased nutrient loads likely to result from increased connections to the BSTP and from any discharge of effluent from the package treatment plants proposed by Gosford Shire Council for communities at Bar Point, Cogra Bay, Wobby, and Patonga, and 3. commences detailed studies of the likely effects of increased nutrient loads on phytoplankton and seagrass in the river. Models of nutrient impacts should also consider the residency time in the estuary of nutrients, heavy metals, estrogens, and other biologically active compounds discharged from the BSTP (e.g., bioaccumulation, accumulation in sediments), as well as any impact on marine life. Moreover, SW has not provided the community with details explaining the poor performance and high cost of the plant, while repeatedly assuring the community since the plant's commissioning that it was operating to specifications. The community needs this information to make an informed decision.
1. Alternatives to increased nutrient levels: SW has ignored suggestions from the community of alternatives to increasing the load of nutrients discharged from the BSTP. These included alternative and modified technologies for the operation of the BSTP, as outlined in submissions from the Dangar Island League and reducing the amount of phosphorous (P) entering the plant. The community is already moving to ban soap powders and detergents with high P levels (e.g., Aldi stores) and a ban on such products in Hornsby and Gosford Shires would be neither onerous nor difficult to implement, while considerably reducing total P loads entering the river from the BSTP and other treatment plants on the lower Hawkesbury River. Before approving the changes to Condition 63, SW should be required to show why reducing inputs is not a practical and cost-effective alternative to increasing discharge levels.
2. Impact models: The documentation provided to the public by SW regarding impacts of increased discharge loads only concludes there are unlikely to be adverse effects (e.g., pp. 22, 38 in SW's submission). There are several deficiencies in the approach taken by SW as to the impact of increased nutrient loads being discharged from the BSTP. Firstly, SW's models fail to consider cumulative impacts of increasing connections to the BSTP, the increase in Sydney's population, with greater total discharges into Hawkesbury-Nepean system, and the nutrients to be discharged from any `package treatment plants' to service the communities of Bar Point, Cogra Bay, Wobby, and Patonga. Statements from SW in their submission that nutrient loads appear to have decreased since SW commenced monitoring of river water quality ~ 20 years ago (e.g., Figure 7 in their submission) have not been substantiated. SW presents no statistical analysis of its data and visual inspection of at least the graphs of Nitrogen (N) and P strongly suggests there are no significant long-term declines. Figure 7 (ammonia) visually suggests a long-term decline, but whether this is independent of periods of high and low rainfall is unlikely and at the least requires statistical analysis. Consideration also needs to be given as to how the data presented by SW were collected, as no detailed methodology is presented in its submission. If SW is relying on water samples taken by locals (e.g., Streamwatch), than the data I have seen has significant gaps over time and samples do not appear (personal observation) to have been collected in a standardized and appropriately rigourous manner.
A major failure of SW from when it first proposed the Brooklyn-Dangar Island Sewerage Scheme was it refusal to measure or model residency time of nutrients discharged into the Hawkesbury estuary. Instead SW has relied exclusively on dilution models (often without proper consideration of more complex river flow patterns, such as the effects of tidal flows in Mooney Mooney Creek) and not taken into account any bioaccumulation of nutrients nor the fact that tidal currents may cause nutrients to remain within the estuary for greater or shorter periods of time depending on tide and weather conditions.
Of equal significance is the failure of SW to measure and model impacts of other chemicals, such as estrogens, which can occur in domestic sewage at high concentrations and are known globally to have significant adverse impacts on aquatic organisms. Domestic sewage can also contain high concentrations of heavy metals, such as cadmium, and, increasingly, nanno particles. SW appears to have data on any of these materials and their likely effects on the river. Although SW is not requesting permission to increase the loads of these compounds discharged from the BSTP, it should be required to consider the totality of its impacts on estuarine health, not consider each compound, nutrient, or chemical separately. Ecosystems simply do not work that way.
3. Impacts on phytoplankton and seagrass: Two of the most important components of any estuarine ecosystem are phytoplankton and seagrass. Both are likely to be highly responsive to changed nutrient loads within the estuary. However, SW has consistently ignored advice that it should include phytoplankton and seagrass as core components of its monitoring of effects from the discharge of effluent from the BSTP. Instead it has chosen to monitor hard bottom fouling organisms on the pylons near the discharge point, but these organisms are primarily detrital feeders and unlikely to respond to changes in nutrient loads, although higher plankton concentrations will increase growth rates. In its last response explaining why there is no need to monitor seagrass in the Hawkesbury estuary, SW said there were no seagrasses near the discharge point. This ignores the extensive seagrass beds around Dangar Island, in Mullet Creek, and at Wobby Point, not to mention smaller beds near Brooklyn and at the mouth of Sandbrook Inlet (very close to the discharge point) and the fact that the community has already invested considerable resources in protecting these seagrasses. It also shows a lack of understanding as to how nutrients, at very low concentrations perhaps, move around an estuary and can have significant effects on phytoplankton and seagrasses.
According to the marine biologists I consulted at Edith Cowan University, `There is no standard or clear understanding about how much nutrient, loads or concentration will negatively affect seagrasses, it is very much dependent on the location.' However, increased nutrient loads are implicated in the decline of seagrasses globally. One impact of increased nutrient levels in an estuary is increased productivity of phytoplankton and organisms growing on seagrasses. Both can diminish the light reaching the seagrass leading to decline and death of seagrass. Seagrasses in the lower Hawkesbury are presently continuing to recover from the high silt loads carried down stream from in-bed sand mining and poor construction practices within the catchment from the 1940s into the 1980s that diminished the light penetrating to the seagrasses. It is important that nothing be permitted to happen that will reverse this by increasing turbidity (e.g., higher plankton concentrations) or increased fouling of the seagrasses by epiphytic organisms.
According to the biologist consulted at Edith Cowan University, `The important question to ask is will the increased nutrients stimulate phytoplankton or algal epiphytes that will then reduce light and adversely affect seagrasses. If it is predicted that phytoplankton will be stimulated, what will the resultant light attenuation be? We do have a better understanding about the light requirements for seagrasses. I am guessing it is Zostera in the Hawkesbury, Zostera muelleri=capricorni has a high light requirement ~ 35% (minimum light requirement (MLR) in Photosynthetic Photon Flux Density (PPFD - light with wavelength (** of about 350-700 nm) ) and a high compensating irradiance of 80-92 muE m-2 s-1( PHOTOSYNTHETIC CHARACTERISTICS OF SEAGRASSES (CYMODOCEA-SERRULATA, THALASSIA-HEMPRICHII AND ZOSTERA-CAPRICORNI) IN A LOW-LIGHT ENVIRONMENT, WITH A COMPARISON OF LEAF-MARKING AND LACUNAL GAS MEASUREMENTS OF PRODUCTIVITY Author(s): POLLARD, PC (POLLARD, PC); GREENWAY, M (GREENWAY, M) Source: AUSTRALIAN JOURNAL OF MARINE AND FRESHWATER RESEARCH Volume: 44 Issue: 1 Pages: 127-139 Published: 1993). As this is a meadow [seagrasses near Dangar Island] that has been impacted before, any significant light reductions are very likely to affect rates of recovery. If any modelling has been done on nutrient dispersal and phytoplankton responses, then it should be possible to factor light attenuation into it too.'
Unfortunately, SW has ignored all advice regarding monitoring plankton and seagrass in the lower Hawkesbury estuary. Hornsby Shire Council has only initiated monitoring of plankton loads (chlorophyll levels) in the last year or so. As a result there are inadequate background data to determine whether even the present outputs from the BSTP are having an effect on these core components of the estuary, much less failing to consider other existing and proposed sources of nutrients entering the estuary. Proposing increases in nutrient loads in the absence of such data amounts to `environmental vandalism'.
SW's proposal, if approved, has the potential of reversing nearly 20 years of effort on the part of government and community to improve water quality in the Hawkesbury-Nepean system. While SW seemed focussed on relatively modest cost savings, the real costs to the estuary and people of New South Wales from the environmental impacts of increased nutrient levels from the BSTP have the potential to be much higher, with losses of amenities, recreation value, biodiversity, and fisheries all following from any increases in plankton loads and any decline in seagrass.
Emeritus Professor Harry F. Recher
Edith Cowan University
c/ POB 154, Brooklyn, NSW 2083
