Summary
Two significant and related issues confronted the managers of the Hill End water and sewage scheme: the potential for water shortages and the surcharge of untreated sewage to the environment. These concerns are particularly relevant during peak tourist periods. Urban Water Cycle Solutions was commissioned by the NSW Department of National Parks and Wildlife Services to evaluate the efficacy of the water and sewerage scheme that services the town of Hill End. The report reviewed and collated existing information provided by DNPWS into a synopsis that identifies main issues and important gaps in knowledge. The overall objectives of the investigation was to achieve optimum operation of the water and sewerage schemes such that a reliable and safe water supply is provided, wastewater discharges to the environment are minimised and sustainable funding of the schemes. An equally significant goal is to create ecologically sustainable approach to the management of the water and sewerage schemes.
Introduction
The township of Hill End was established during the 1880s due to the discovery of gold in the area and in 1967 part of the town known as the historical village of Hill End was proclaimed as a historical site. Hillend is located about 70 km northwest of Bathurst and 69 km south of Mudgee.
Water supply and sewerage disposal schemes were constructed by the Department of National Parks and Wildlife Services (DNPWS) prior to the proclamation of the village of Hill End as a historical site. The DNPWS own and manage the historical village of Hill End including the water and sewerage schemes. The surrounding areas are managed by Evans Shire Council.
The majority of permanently occupied tenements within the historical village of Hill End are connected to reticulated water and sewerage systems. All of the dwellings are also connected to rainwater tanks and septic tanks. Houses outside of the historical village of Hill End rely on rainwater tanks for water supply and septic tanks for wastewater management.
Outstanding heritage values exist in the historical village of Hill End including a museum, historical buildings, old mine sites, camping grounds, a hotel and bed and breakfast accommodation that serve to attract a large volume of visitors to the area during school holidays and weekends.
Rainfall at Hill End is recorded using daily readings from an accumulating rain gauge located at the visitors’ centre. During the period 1988 to 2002 the average, maximum and minimum rainfall depth recorded was 804 mm, 1248 mm and 500 mm respectively. Even in the driest years the town has sufficient rainfall to ensure that drinking and cooking demand is adequately supplied by rainwater tanks in most circumstances.
Population and water demands
Water supply data from the reticulated network provided by the NSW government was used to establish that 84 people currently occupy 37 dwellings in the historical village of Hill End. This population includes 55 permanent residents occupying 23 dwellings and 29 occasional residents that occupy 14 dwellings. About 14,015 people also visited the town and signed the visitors’ book in 2002. It is also noted that 26 people attend the school during week days in the school terms. Note that DPWS (2000) estimated that 60 students attend the school.
Historical records from 1996 revealed that 58 residents occupied 31 dwellings in the historical village of Hill End and the town received about 16,000 visitors. The population included 39 permanent residents that occupied 22 dwellings and 19 occasional residents occupy 9 dwellings. The population of the historical village of Hill End has grown by 45% since 1996 and the population of locality of Hill End has increased by 20% since 1991.
Visitors to Hill End from 1997 to 2003
Water use
The majority of dwellings and commercial premises located in the historical village of Hill End have water meters installed. Results from meter readings indicated that water use of dwellings in the historical village was 6.362 ML/annum during the period 1997 – 2002 and metered water use in the village was 3.688 ML/annum in the period 1981 – 1996. There has been a 42% growth in metered water use since 1996.
In 2002 the average water use in dwellings with permanent residents was 214.5 kL/annum, the average water use in dwellings with occasional residents was 90.2 kL/annum and the average water use in the Hotel was 573.6 kL/annum. Note that not all water meters are operational and water use is not regularly recorded.
This study motivated the installation of water meters during September 2002 to buildings that are subject to water use from the visitor population to Hill End. These locations are not subject to rates assessments therefore water demand had not previously been recorded. A full network of water meters was also utilised to locate leaks or unaccounted for water in the Village.
The total annual reticulated water demand for Hill End in 2002 can be estimated to be 7,173 kL. Note that the water reticulation system has been found to be leaking in several locations. Thus the total water demand will be greater than the total of annual readings.
Estimate water use for the town of Hill End
The majority of dwellings in the town of Hill End use rainwater tanks to supply drinking and cooking water demand which is about 5% of total household water demand. Rainwater tanks are also used to supply outdoor water demand. Analysis of the rainfall records for Hill End (daily records measured at the Visitors’ Centre (1988 – 2003) show that rainwater tanks could be used to successfully partially supply other water uses with backup from the reticulated bore water supply as required.
Site inspections at Hill End have established that single flush toilets with a flush volume of 13 litres are installed in most residences and commercial premises. It was noted that the use of water conservation measures such as 6/3 litre dual flush toilets will substantially reduce water demand in Hill End. The replacement of all the 13 litre flush toilet cisterns with 6/3 flush cisterns will reduce water demand for toilet flushing by up to 60%.
The Water Supply Scheme
The NSW Government was licensed to extract up to 40 ML/annum from the aquifer under Hill End for water supply purposes. This water is sourced from four ground water bores located within the town of Hill End. Some of these bores have collapsed due to ground movement that has resulted from past mining activities.
A majority of reticulated water supply to Hill End was drawn from a recommissioned ground water bore located near Clarke Street. No details of the capacity of this bore were provided. However local staff reported that the pump has the capacity to supply ground water at a rate of about 0.8 L/s. In addition the NSW government explained that during periods of low rainfall ground water levels are lowered resulting in reduced flow rates available from bores.
The chlorination of the water supply before distribution to large storages that have significant residence times is not optimum and will result in the need to re-chlorinate the stored water on a regular basis. This can produce water with high chlorine content that has unacceptable quality. Local staff reported that it is indeed necessary to re-chlorinate water on a regular basis. It is highlighted that most residents of Hill End use water from rainwater tanks for drinking and cooking.
The water supply from the Germantown tanks should pass through a filter to remove organics and then chlorinated prior to distribution to Hill End. This would involve reconfiguration of the distribution arrangements at the Germantown tanks and moving the chlorination apparatus from the bore pump to the Germantown tanks. Moving the filtration and disinfection process to after the Germantown storages will allow the storages to act as facilitators of natural flocculation and settlement processes that will remove significant amounts of organics prior to treatment thereby improving water quality.
Water is also transferred via a pump to a storage tank with a capacity of 3 kL in the Glendora Camping Ground that is used to supply water to the camping ground. A 135 kL storage tank near the visitors centre and two 90 kL tanks near High Street are also supplied via the High Street booster pump. The visitors centre, toilet block, workshop and nearby dwellings are supplied with water from the storage tank at the visitors centre. An active ground water bore is located near the Visitors’ Centre but no information is available about water use from this bore. A water meter should be installed on this bore and water extractions should be recorded at 9 am each day.
The Sewerage Disposal Scheme
The locality of Hill End has two different sewerage disposal schemes that service the town of Hill End and Glendora Camping Ground. In both schemes sewage is captured in on-site septic tanks that discharge effluent via small diameter pipes to evaporation ponds. This type of sewage management systems is known as a septic tank effluent disposal scheme (STEDS).
Effluent from septic tanks in the town scheme gravitates via pipes to an underground storage tank that has a capacity of 10 kL near Clarke Street. Two submersible grinder pumps with capacities of 1.28 L/s and 1.09 L/s are located in the storage tank. The smaller pump is used as a backup for the larger pump. Effluent is transferred from the storage via the pump and a 50 mm diameter PVC rising main to the Kitty’s Flat oxidation and evaporation ponds.
The two oxidation ponds have surface areas of 1,460 m2 and 1,196 m2 respectively and the three evaporation ponds with surface areas of 1,958 m2, 3,097 m2 and 4,600 m2 respectively. A small portable pump was used to transfer effluent from the first oxidation pond to the second oxidation pond. This results in limited utilisation of the evaporation ponds for treatment of the sewage effluent. A gravity transfer system using valves and small pipes should be installed to allow efficient transfer of effluent to the evaporation ponds.
The ponds have the capacity to treat about 25 ML of effluent per annum and the DNPWS also have a license from the EPA to discharge effluent from the ponds to the environment. Note that the actual volume of sewage requiring treatment is about 5 ML per annum. Provided that effluent can be efficiently transferred from the oxidation ponds to the evaporation ponds and large volumes of stormwater do not enter the sewerage system, the sewage treatment system is adequate for two reasons:
- The annual sewage volume has been over-estimated by a considerable amount (actual volume: 5 ML/annum, volume used in previous design: about 25 ML).
- The volume of sewerage discharges in traditional systems during wet weather can be up to 15 times normal dry weather sewage discharges due to stormwater infiltrating into the sewerage system. However the use of septic tanks and small diameter pipes (STEDS) to manage sewage eliminates the infiltration of stormwater into the sewage system during wet weather. Thus traditional sewage design assumptions will significantly over-estimate the volume of sewage discharges in Hill End.
A number of manholes have been placed in the sewage reticulation system that runs along Clarke Street. Whilst the use of manholes is advisable at bends and junctions to allow removal of blockages the use of manholes also allows stormwater into the sewerage system resulting in surcharges of sewage to the environment. A number of additional manholes have been placed at intervals in straight sections of the sewerage reticulation system (especially in Clarke Street) and the tops of these manholes are below ground level. Thus the risk of sewage surcharges was greatly increased. Indeed the imperviousness of the Hill End sewerage scheme to stormwater infiltration is compromised by the presence of the manholes. Note that the NSW Government reported that the Clarke Street bore had been previously closed down due to faecal contamination of the water. It is most likely that the faecal contamination resulted from sewage surcharges.
The majority of manholes in straight sections of the sewerage reticulation system are redundant. It is recommended that pipe sections with inspection points be placed in those manholes to provide a sealed connection through the manholes. The remaining manholes that are placed on bends or at the intersections of sewerage pipes in the lower reaches of the sewerage system should be sealed with an appropriate sealant to avoid ingress of stormwater into the sewerage system.
Three houses in Germantown do not have adequate sewer management facilities. It is proposed to convey effluent from the existing septic tank at Rose Cottage in a gravity reticulation system with small diameter (50 mm) pipes towards the Village Camping Ground. A septic tank with a capacity of 3 kL will be placed in the grounds of Miller’s Cottage to collect sewage from Miller’s Cottage and the adjoining cottage. Effluent from the new septic tank will be collected in the new gravity reticulation system that falls towards the Village camping ground. It was also recommended that 6/3 litre dual flush toilets be installed at both houses to reduce water demands and sewage discharges.
The proposed Germantown sewerage scheme
Two significant and related issues confronted the managers of the Hill End water and sewage scheme: the potential for water shortages and the surcharge of untreated sewage to the environment. These concerns are particularly relevant during peak tourist periods. The availability of the ground water resource is unknown but will be variable and the performance of the Kitty’s Flat sewage facility will also vary in accordance with climatic conditions. Both issues can be addressed by use of water efficient appliances, elimination of water leaks, and reuse of effluent for toilet flushing and irrigation purposes within the town of Hill End.
It was proposed to use treated effluent to flush toilets in the Village Camping Ground and for toilet flushing in all nearby buildings subject to high tourist visitations. It is also proposed to use the treated effluent to irrigate the commons and the Village Camping Ground. The annual water demand for toilet flushing at the Village camping ground is about 114 kL with a peak daily water demand for toilet flushing of about 4 kL. In addition the annual water demand for irrigation of the commons and the camping ground will be dependent on the area subject to irrigation but it will be reasonable to assume that about 400 kL per annum will be used for irrigation. Thus the proposed scheme will, at a minimum, reduce annual water demand by about 114 kL and reduce annual sewage discharges by about 514 kL. A schematic of the treated wastewater reuse scheme is shown below.
Schematic of the proposed Village treated wastewater reuse scheme
The Glendora Camping Ground has a separate sewerage system that services the amenities block. Wastewater from the amenities block discharges to a large septic tank that overflows via a gravity reticulation system to an oxidation pond and an evaporation pond. The average sewerage discharge from the amenities block is 141 L/day and the peak daily sewerage discharge is 3.2 kL/day. The average and peak water demands at the amenities block are similar.
The ponds are located in the upper reaches of a water supply catchment and the ponds have small surface areas that provide limited opportunity for oxidation and evaporation. As a result the ponds remain full and during rainfall events are likely to overflow.
The important issue to be resolved at the Glendora Camping Ground is to ensure that the ponds do not overflow into the water supply catchment. This was achieved by intercepting the effluent discharging from the septic tank for treatment and reuse in toilets at the amenities block and for irrigation of the grounds. The ponds would remain in the system as a backup to store excess effluent for short durations during peak periods and the treated wastewater irrigation system can be optimally employed to ensure that effluent levels in the ponds is kept to a minimum. A schematic of the wastewater treatment strategy is shown below.
The proposed Glendora wastewater treatment scheme
Conclusions
A number of solutions were proposed for the improvement of the water and sewage systems at Hill End including a conventional wastewater disposal and treatment system, removal of all septic tanks, removal of rainwater tanks and total reliance on an improved reticulated groundwater system. However the town’s limited budget for new infrastructure excluded many of the proposed conventional solutions. The list of feasible solutions included the integrated water cycle management (IWCM) solution were:
- Install water efficient toilets
- Install rainwater tanks for toilet flushing at the hotel and public toilets
- Install water filtration and disinfection at water distribution tanks
- Make sewage manholes impervious to stormwater inflows
- Connect all properties to the common effluent scheme (STEDS)
- Establish an effluent reuse scheme
- Only discharge excess effluent that is treated to high quality to waterways
- Install water meters and implement a program of daily observations to refine management strategies
- Eliminate leakage from the water distribution system
