diversion of wastes to the Hawera WWTP in the 2010-2011 period, discharges from the Eltham
WWTP now occur only as a result of high rainfall events that exceed the storage capacity of the primary and
holding ponds, and the pumping capacity of the reticulated system to Hawera.
Analysis of the primary pond effluent was not required during the monitoring period, although the
condition of the pond and any associated odour continues to be monitored during routine inspections.
Along with a visual
Application AEE x14 Consents Manawa Energy 14 February 2023
the tributary (WIT000460) exceeded the historical maximum count for that site. High
counts such as these are typically associated with heavy rainfall and the resultant
increase in agricultural runoff. However, the lack of precipitation prior to sampling
page
14
indicates that rainfall was not a significant factor in these results. As the counts were
high at sampling sites upstream of the septic tank and sewage pump station it is
unlikely that these results would be due
effects. Ring drains and bunds
were clear and fit for purpose. Everything was satisfactory.
23 May 2013
Inspection was undertaken following significant rainfall in previous days. The skimmer
pit contained discoloured water as a result of run-off from construction activities at the
site. There were no visual effects from this discharge on the receiving waters. The ring
drain near the generation unit had a section of damaged plastic liner. The newly
constructed ring drain on the eastern boundary
results for stormwater samples collected on
05/10/23 and 07/10/23. Hydrocarbon results were BRL and
within consented limits.
• Confirmation with site that normal operational activities
were occurring at the time and there were no heavy rainfall
events that may have caused a ‘flush through’.
10-Oct-23
Self-notification
was received that
the results of a
further
stormwater
sample were also
above the
hydrocarbon
consent limit
(24.3mg/L).
N No
Additional
is 10 L/s. However as a result of stormwater inputs to the pond, the discharge
rate from the pond to the Mangorei Stream will be highly variable as it is dependent on weather conditions.
The size of the pond will allow storage for a 10% annual exceedance event (AEP) event. The maximum
discharge rate from the pond during large rainfall events is 1,060 L/s as this is dictated by the size of the
page
5
outfall pipe (750 mm). However there is also provision for the pond
combination of native and indigenous forestry, with the
afforestation plan for the entire parcel attached to Mr Gibson’s evidence.
34. The Haehanga enters the Mimitangiatua about 780 m downstream of the
site office and about 100 m downstream of SH3/Mokau Road.
35. A key feature of the existing site is the drainage that has been put in place
to ensure clean water running off the hills in rainfall events is diverted
around the active site areas.
36. The wider catchment of the
devices shall be telemetered and report the data electronically to the Chief Executive once
per day, and shall include the rainfall data at hourly intervals from the station established at
the Mangaotea Road culvert.
A land use consent for the damming of the Mako Stream via an existing dam structure to form
Lake Ratapiko for hydro-electric power generation purposes, including the service and auxiliary
spillway structures
page
Trustpower – Proposed Conditions
also noted that attempts had been made to prevent discharges to ground by placing a plastic liner
under a unit. Unfortunately the control fell short of being useful because there were no sides that would act
as a bund, therefore during a rainfall event any discharges onto the liner would become entrained in
stormwater and flow onto the site. Staff needed to know how to correctly install a bund, with a process set
up to ensure that this activity could be carried out correctly by anyone in the
Normally these discharges are in batches with a frequency ranging from daily to weekly, dependent on
rainfall. During and after exceptionally heavy rainfall, the discharge may occur for continuous periods of up
to 24 hours.
In 2021-2022, the maximum daily volume of stormwater discharged from the site was 6,063 m3/d following
rainfall of 120 mm and 87 mm. Given the extremely high rainfall and that there was only one minor non-
compliance instance above the 6,000 m3/d limit the Company was