Fremantle Port Inner Harbour and Channel ... - Fremantle Ports

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Management measures shall be implemented to neutralise return water to
within acceptable pH range.
Return water discharge shall cease until it can be demonstrated that no risk to
the environment is posed from unacceptably low (or high) water pH.
Dissolved Oxygen within proximity of Inner Harbour Dredge, Return Water, Offshore
Dredge and Disposal Plumes
Frequency
• Baseline prior to dredging or discharge of reclamation water, then weekly (or
fortnightly at Inner Harbour sites monitored by DoW) until the completion of dredging
or reclamation and conclusion of return water discharge, and one week thereafter or
until water quality meets relevant criteria.
• Monitoring will be targeted and focussed on data collection at those sites within
proximity of the visible plume/s (as based on field observation and aerial imagery),
which technically defines the potential zone of influence, plus associated reference
sites. That is, not all sites may be sampled, and to reiterate for emphasis, when
dredging only those sites within proximity of the visible dredge, disposal and/or return
water plumes will be sampled, plus associated reference sites.
Location
Total of twenty-one sites including:
• Four ‘dynamic transect’ sites within the Inner Harbour dredge plume (at distances
10 m, 50m, 100 m and 500 m from dredge head) as detailed in Section 3.3,
Figure 3.1 and Figure 3.2 (N.B. ‘mock’ sites at the same distances of separation along
a transect within the Inner Harbour, at a random location overlying the footprint of
potentially contaminated sediment, shall be used for (i) baseline sampling and (ii)
water quality sampling in the week subsequent to dredging of that sediment, if the
dredge has moved out of the Inner Harbour).
• Six sites including one site within the reclamation pond, one site within the weir box,
three ‘dynamic transect’ sites within the return water plume (at distances 10 m,
200 m and 500 m from silt curtain) and two ‘static reference’ sites within the
Cottesloe Reef Fish Habitat Protection Area, as shown in Figure 3.1 (N.B. ‘mock’ sites
at the same distances of separation along a transect offshore of the return water
discharge outlet / weir box, shall be used for (i) baseline sampling and (ii) water
quality sampling in the week subsequent to conclusion of return water discharge).
• Three water quality sites surrounding the Inner Harbour, monitored by the DoW, as
detailed in Section 3.6 and Figure 3.1 (N.B. salinity and total nutrients will also be
monitored by the DoW at these sites for contextual purposes).
• Eight ‘dynamic transect’ sites within the offshore dredge plume (4 sites) and disposal
plume (4 sites) (at distances 10 m, 50m, 100 m and 500 m from dredge head or
location of spoil disposal) as detailed in Section 3.4 and Figure 3.1 (N.B. ‘mock’ sites
at the same distances of separation along a transect within the offshore deep water
channel and disposal area, at a random location overlying the footprint of sediment to
be dredged and disposed shall be used for (i) baseline sampling and (ii) water quality
sampling in the week subsequent to dredging and disposal of that sediment).
Method
• Measure daytime DO saturation within bottom waters (0-50 cm from sediment
surface) at each site every week (or fortnight at DoW sites) in accordance with EPA
(2005a,b).
• For contextual purposes TSS concentration will also be determined at each location by
collection of a single integrated-depth water sample, sent to a NATA-accredited
laboratory for analysis of the concentration and determination of the organic
component via loss on ignition (LOI).
• For contextual purposes the water turbidity (NTU) and temperature profile will also be
measured at each location.
• For contextual purposes, Secchi depth will also be measured at each site in
accordance with EPA (2005a,b).
• Compare rolling 2-week median DO saturation of bottom waters at each potential
impact site against EQG triggers for moderate and high protection as listed in
Table 4.4.
24 Oceanica: Fremantle Ports: Inner Harbour and Channel Deepening - Water Quality Monitoring Program