Whitehead & Associates Environmental Consultants Pty Ltd PO Box 23 Bellingen NSW 2454 Australia Telephone +61 2 6655 9623 Facsimile +61 2 6655 9623 Email [email protected]Mr Warren Harriss Kempsey Shire Council Kempsey NSW 2440 Our ref: 1064b 280415sd 28 April 2015 Stormwater Infiltration Investigation – Stuarts Point Holiday Park, NSW 1. Introduction Whitehead & Associates (W&A) were commissioned by Kempsey Shire Council (KSC), to undertake a stormwater infiltration investigation and updated review of the On-Site Sewage Management System (OSMS) infrastructure at Stuarts Point Holiday Park (SPHP), Stuarts Point, NSW (Site). 2. Scope of Work Works were undertaken in accordance with our proposal dated 25 February 2015. W&A staff reviewed the provided flow meter data, previous available data on file, and then inspected the Site to assess potential stormwater and OSMS issues, then directed Round The Bed Plumbing to undertake CCTV inspections at those locations. Limited dye testing was also undertaken by W&A. 3. Results 3.1 Flow Meter Data A summary graph was provided by KSC (attached). The graph includes data from flow meter readings obtained of throughput of the FujiClean PTP, plus recorded rainfall, and limited water usage and occupancy data (Table 1). Table 1. Graphed Data Provided by KSC Date Range Flow Readings Rainfall Site Water Usage Site Occupancy 29/12/13 – 31/1/15 Yes Yes - - Mid Dec 2014-Late Jan 2015 - - - Yes Mid Jan 2015-Late Jan 2015 - - Yes - Whitehead & Associates Environmental Consultants Pty Ltd 1
PO Box 23 Bellingen NSW 2454 Australia Telephone +61 2 6655 9623 Facsimile +61 2 6655 9623 Email [email protected]
Mr Warren Harriss Kempsey Shire Council Kempsey NSW 2440 Our ref: 1064b 280415sd 28 April 2015
Stormwater Infiltration Investigation – Stuarts Point Holiday Park, NSW
1. Introduction Whitehead & Associates (W&A) were commissioned by Kempsey Shire Council (KSC), to undertake a stormwater infiltration investigation and updated review of the On-Site Sewage Management System (OSMS) infrastructure at Stuarts Point Holiday Park (SPHP), Stuarts Point, NSW (Site).
2. Scope of Work Works were undertaken in accordance with our proposal dated 25 February 2015. W&A staff reviewed the provided flow meter data, previous available data on file, and then inspected the Site to assess potential stormwater and OSMS issues, then directed Round The Bed Plumbing to undertake CCTV inspections at those locations. Limited dye testing was also undertaken by W&A.
3. Results
3.1 Flow Meter Data A summary graph was provided by KSC (attached). The graph includes data from flow meter readings obtained of throughput of the FujiClean PTP, plus recorded rainfall, and limited water usage and occupancy data (Table 1).
Table 1. Graphed Data Provided by KSC Date Range Flow Readings Rainfall Site Water Usage Site Occupancy 29/12/13 – 31/1/15 Yes Yes - -
• Water consumption based on the limited data over January 2015 was between approximately 32-48kL/day. This correlates with the water consumption figures provided previously by KSC for quarterly data from November 2007 to March 2011 of 12kL/day to 49kL/day depending on seasonal usage;
• During a window of no rainfall in mid-January, wastewater throughput at the PTP ranged between 74-82% of the limited water consumption values. This correlates well with the wastewater generation ratio estimate of 80% of water usage that W&A applied in a previous audit of the Site1;
• Wastewater throughput at the PTP has a base value of 8-17kL/day, typically around 15kL/day, with seasonal spikes in April of around 39kL/day and October of 20kL/day;
• A spike wastewater throughput of 40kL/day was recorded in late July 2014, a day following 40mm rainfall event, preceded by 92mm rainfall in 24hrs, and 48mm in 48hrs;
• A spike wastewater throughput of 53kL/day was recorded in over Christmas/New Year 2014/2015 that corresponded with peak occupancy and three days of rainfall of 24mm, 30mm and 60mm;
• A comparison of the Christmas 2013 and 2014 peaks indicates that rainfall for Dec-Jan 2013/2014 was 75mm in total with peak wastewater throughput of 46.6kL/day, whilst rainfall in Dec-Jan 2014/2015 was 483mm in total with peak wastewater throughput of 53kL/day;
• Investigations by Truewater Australia in early 20132, including installation of a flow meter and recording of final irrigation pump run times, confirmed that pump run times increased from a base load rate of around 50mins/day up to 200 mins/day in the day following rainfall; and
• The increased daily wastewater throughputs within 24hrs of a medium rainfall event (>60mm) or a more prolonged lower rainfall event seems to generate a sustained spike of wastewater flows. This suggests a combination of base wastewater generation loading (occupancy derived) and weather loading from groundwater seepage or intermittent overland stormwater flow seems to be present within the OSMS;
Given these results and historical 2007-2011 data, W&A confirm that the best estimate of wastewater production is still ~12kL/day low season, ~18kL/day shoulder season, and 42-47kL/day over short peak periods. The peak load has been revised slightly upwards based on the 2013/2014 data. This wastewater production is being augmented and diluted by rainfall infiltration into the OSMS, and removal of the infiltration source is critical to ongoing reliability of treatment.
1 Upgraded Wastewater Management for Stuarts Point Holiday Park, NSW. Revision B, dated 18/11/13. 2 Truewater Australia, Tender Submission to Kempsey Shire Council for SPHP OSMS Design and Install/ TQE13/13.
3.2 Package Treatment Plant W&A inspected the FujiClean PTP on 27th February 2015. The distribution well appears to be working satisfactorily with surprisingly limited scum, and each of the CE-6000 FujiClean treatment pods appeared to be operating with no undue frothing, overflows, poor sludge return etc. The FujiClean CE-6000 treatment pods have a combined treatment capacity of 24kL/day at design specification. The 2013 tender document from the supplier/installer, Truewater Australia provided the range of treatment capacity and effluent quality expected from the 4 CE-6000 pods proposed to be installed (Table 2).
Table 2. Predicted PTP Treatment Ability
Quality Units Typical Secondary
Quality1
Truewater FujiClean Product
Brochure
Truewater <24kL/day2
Truewater 36kL/day3
Truewater 43.8kL/day4
BOD mg/L <20 <20 <10 <20 No data
TSS mg/L <30 <20 <10 <30 No data
Faecal Coliforms
cfu/100ml <30-1,000 No data <10 No data but chlorine disinfection
Total Nitrogen mg/L <35 <10 <10 <30 No data
Total Phosphorus
mg/L <15 <10 <10 <15 No data
Free Chlorine mg/L >0.2, <2 No data No data but chlorine disinfection
Dissolved Oxygen
mg/L >2 No data No data No data No data
Oil & Grease mg/L <3 No data No data No data No data
1. DLG 1998
2. Truewater Tender Page 11. Assumed influent of BOD <200mg/L, SS<160mg/L and TN <45mg/L
3. Truewater Tender Page 15 for 36kL/day at “Secondary” Quality.
4. Truewater Tender Page 15. No value provided for >36kL/day, but assumed to be better than primary and less than secondary quality.
The design specification by W&A for the PTP had been for secondary quality at 42kL/day without disinfection, with further polishing undertaken passively in an at-grade Wisconsin sand mound3. Due to budgetary constraints, it is understood by W&A that KSC subsequently decided to not upgrade the LAA and maintain the existing two pressure dosed discharge control beds. Based on the data provided in the accepted tender that the Fujiclean can produce above secondary quality at 24kL/day, the selected design is expected to produce
3 Upgraded Wastewater Management for Stuarts Point Holiday Park, NSW. Dated 15/1/13.
secondary quality around 24-30kL/day, but operating at any more than 24kL/day would possibly void the manufacturer’s warranty, something to consider. W&A do not have effluent quality data to confirm variations in effluent quality for the PTP under different flow regimes, but secondary quality is unlikely to be achieved during peak 42-47kL/day flows with the current PTP sizing. W&A were asked to comment on draining fish cleaning waste from near the camp kitchen to the PTP. As a general comment, the direct application of a small amount of fish offal and washdown water should not be affecting the adjacent water quality. It may though affect the distribution of opportunistic organisms in the vicinity of the outlet pipe. If draining to the sewerage system, the volume of offal and water that will be generated is expected to be insignificant, perhaps 100-300L/day, and will not substantially affect PTP performance. Fish offal will have slightly higher BOD than general domestic waste, but given the low volumes, again will not substantially affect PTP performance. Fish scales should be macerated by the pumps in P7 prior to pumping to the PTP, but may cause some clogging issue with pumps and media, though again given the small volumes this risk is low. It is recommended that a coarse filter trap be constructed beneath the scaling table to catch the majority of coarse particles and binning for waste collection
3.3 Land Application Area W&A inspected the LAA in 2013 as part of the audit of the Site and confirmed that surface expression of effluent is not occurring, even though the existing two beds are highly loaded. Permeability testing undertaken by W&A at that time confirmed that the sand subsoils are highly permeable, meaning that the higher loading of effluent is likely deep percolating to groundwater. In the Revision B of the W&A audit document (November 2013), a revised design was recommended that supplemented the existing pressure dosed discharge control beds. It is understood that these have not been constructed but were planned for the 2015-2017 financial years as funding became available. In the interim W&A recommended installation of two additional groundwater monitoring wells to the existing three well network, and six monthly sampling to monitor any groundwater contamination issues. The revised design by W&A requires amendment based on 2013/2014 data of peak wastewater flows reaching 47kL/d. The existing bed area is 324m2, and an additional 617m2 basal area is required to ensure soil loading rates are maintained at manageable levels. These calculations assume no stormwater infiltration into the sewerage system.
3.4 Site Inspection Strider Duerinckx of W&A attended the Site on Friday 27th February 2015. All amenities, pumpwells and septic tanks were inspected in and around the Site (Figure 1 attached). Andrew from RTBP inspected the Site and undertook CCTV inspections over 2 occasions in late March. Photographs 1-9 highlight some features observed, sketches of the northern and southern amenities area are provided in Figures 2 and 3, and a summary of the observations and recommendations are provided in Table 3.
Ceramic pipes are still located at the toilets and exiting the northern side of the amenities, but PVC lines have been installed outside concrete slabs.
Southern side of amenities, poor join work with ceramic and root ingress.
On southern side, drain holds water under concrete slab, and failed o-ring seal at IO may be allowing stormwater ingress as downpipe outlet is directly above.
From southern side, drains directly to Septic Tank T2, and at 13.5m from T2 is holding water and at 3m from tank starts to rise to tank inlet. Sedimentation evident.
Rear western side of block, two surface gullies are flush or below ground level and could accept stormwater runoff or overflow from blocked roof guttering. One gully pipe extends into air for 1m and is open at top.
Northern exit of drains are a mix of PVC and ceramic, and holding water. A small collection well is present. A campervan dump-point is present, open to rainfall collection.
A rectangular septic tank T1 is present in moderate condition with no obvious leaks, but distribution box on northern outlet of T1 has water inflow at base and shows major stormwater ingress by surface runoff from residence.
Ceramic pipework is present on the outlet of the distribution box, but PVC pipework has been installed to the Pumpwell P2.
Septic tank T2 was observed to be flooded with water level over inlet levels. RTBP did not CCTV.
Repair/raise gullies to prevent surface stormwater infiltration. Suggest chinaman’s cap also to limit potential gutter overflow affects.
Replace gutter to larger flow capacity and include gutter guard to prevent blockage.
Repair joins on southern side of amenities including broken o-ring. Assess if downpipe is able to be relocated.
Replace all ceramic pipework on northern side of amenities, decommission the collection well and septic tank T1/distribution box and drain all wastewater directly to Pumpwell P2.
Decommission septic tank T2 and re-lay PVC pipework with appropriate grade into Pumpwell P2 from southern side of amenities.
Provide canopy over dump point on northern side of amenities.
Remove existing mature paperbark tree adjacent to Pumpwell P2 to limit root ingress. Clear vegetation around pumpwell and ensure minimum 100mm height to lid level is maintained to prevent stormwater ingress.
Tank T3 Septic tank is blocked up and sitting above outlet level. RTBP did not assess so cause of blockage is unknown.
Decommission the septic tank and extend discharge line directly to Pumpwell P2.
Southern amenities.
PVC IOs are present, plus toilet connections are PVC. CCTV confirmed all PVC lines, but three separate lines run from mens, ladies and laundry and joining into one line just prior to main Pumpwell P7. Pipework poorly joined
Extend 150mm pipe up alongside southern side of amenities and join all three mens, ladies and amenities into this one line.
Provide canopy over dump point on southern side of amenities.
Location Comments Recommendation and holding water and may also be rising to final 150mm main line.
Dye testing and CCTV undertaken or stormwater drain in passageway between amenities and disabled toilet. Crushed 90mm line observed adjacent to rock wall at river edge, preventing discharge. Manager reports this blocked line contributes to surface flooding at the amenities, and there is a tenuous implication that this could also contribute to stormwater ingress into sewerage lines.
Repair blocked stormwater line at river edge.
Sullage pickup stations
Many concrete slabs are partly buried, allowing stormwater runoff to enter sullage pickup lines that have been constructed flush with the concrete.
Raise slab or construct concrete or wooden lip around all slabs that do not have 100mm clearance to groundsurface
Provide plugs and caps for sullage connection points that have chain affixed (to prevent loss), that limit stormwater infiltration during high rainfall.
Pumpwell P3 At P3 cable was damaged and switch hanging low. After rehanging, duty pump permanently on.
Replace with 4 float switches as per Pumpwells P4 and P6. 2 for duty and 2 for standby. Preferable is also an alternating duty/standby controller for all pumpwells. Pumpwell P5 In P5, effluent levels were high and
switch not turning pump on.
Photograph 1. View of northern side of northern amenities with mix of older sewerage infrastructure (collection well and septic tank), and interconnected ceramic pipework.
4. Conclusions The review of the provided water usage, wastewater flow, occupancy, and rainfall data has confirmed that peak wastewater generation should be around 42-47kL/day over the Christmas/New Year period, and additional wastewater flows of up to 53kL/day recorded in the 2014/2015 peak was a combination of occupancy and stormwater contribution. The investigation by W&A, in conjunction with RTBP, has highlighted a number of likely stormwater infiltration pathways into the sewerage system at SPHP, plus a number of operational issues including:
• Poor connections between ceramic and PVC pipework at the northern amenities;
• Partially buried gullies and poorly sealed inspection points;
• Redundant and partially buried septic tanks (T1-T3);
• PVC pipework laid at poor grade and holding water/sediment at the southern and northern amenities;
• Blocked stormwater line at the southern amenities;
• Partly buried sullage pickup points; and
• Faulty water level/switch sensors at pumpwells. The repair of these items, and removal of redundant infrastructure will improve the OSMS operation and remove stormwater infiltration potential. Eventual replacement of the northern amenities should also be considered to allow all pipework in that area to be renewed. The existing PTP installed is undersized to treat effluent to a secondary quality during peak loading, though is of sufficient capacity for about 95% of the year. Either the capacity of the treatment plant should be increased or measures devised to reduce flows over the short three week peak period either by pumper truck removal or balance tank installation. W&A recommend two more 6kL/day Fujiclean pods be installed, raising the capacity to 36kL/day, and then effluent quality and quantity monitoring undertaken over Christmas 2016 to confirm that secondary quality is achieved. To save on costs, it is recommended that only three units should be running for the remainder of the year, and the final three brought instream two weeks prior to a peak load (April and Christmas), and seeded with activated sludge from the active three systems. The existing land application area is significantly undersized for peak wastewater loads, and additional beds should be installed. An additional total 617m2 bed area is required based on available data, and should be installed prior to Christmas 2016. Yours sincerely,
Strider Duerinckx Senior Eng-Environmental Geologist Attachments: Graphed data Figures 1-3
