DRAINAGE DISCHARGE AGREEMENTS A WAY OF MANAGING RISK Mr. Sam Green Goulburn-Murray Water

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1 Abstract.: 112 DRAINAGE DISCHARGE AGREEMENTS A WAY OF MANAGING RISK Mr. Sam Green Goulburn-Murray Water ABSTRACT Goulburn-Murray Water (G-MW) owns, operates and maintains an extensive regional drainage network. This network provides a drainage service to irrigation customers, towns, roads, businesses and industry. Each of these has their own particular water quality and quantity issues that G-MW must consider when permitting access to the network. The removal of irrigation induced rainfall runoff is the main reason that G-MW manages drains. The drains are sized to receive the quantity of water coming from a rural catchment for a specific rainfall event within a defined time period. The rate at which other sources of inflows can be accepted are assessed against this rural runoff rate. Poor drainage water quality from irrigated agriculture and its impacts on receiving waterways has long been recognised. G-MW and the Goulburn Broken and rth Central Catchment Management Authorities are actively implementing works and activities to improve drainage water quality. The Memorandum of Understanding for Irrigation Drainage Management and Water Quality (IDMOU) specifically addresses this. For other types of drainage customers G-MW uses a risk based approach to assess whether or not an inflow to the drain can be accepted and under what conditions. This paper will show how G-MW uses risk based drainage discharge agreements to ensure that it can assess and effectively manage connections to its drainage network whilst minimising administration and compliance costs. INTRODUCTION Goulburn-Murray Water (G-MW) is responsible under the Water Act 1989 for supplying drainage services to its gravity irrigation customers. It owns, operates and maintains an extensive regional drainage network across the Goulburn Murray Irrigation District. Conveyance of other forms of drainage water is not part of this service, however, in the northern plains landscape this drainage network is often the only form of regional drainage and, by default, G-MW s network provides a drainage service to irrigation customers, towns, roads, businesses and industry. Each of these customers has its own particular water quality and quantity issues that G-MW must consider when permitting access to its network. Under section 199 of the Water Act, G-MW must perform its functions as a regional drainage authority in an environmentally sound way. Its functions area) to provide, operate and protect drainage systems, including the drainage of water into all designated waterways and all designated land or works within its district and, with the consent of the Minister, the drainage of water from that district into any waterway outside that district; b) to develop and implement programs for the protection and enhancement of instream uses; c) to investigate, promote and conduct research into any matter related to its functions, powers and duties in relation to drainage; d) to educate the public about any aspect of drainage. Presented at the Irrigation and Drainage Conference 2009, Irrigation Australia Ltd. Swan Hill, Vic, Australia, Oct of 9

2 The Memorandum of Understanding for Irrigation Drainage Management and Water Quality (IDMOU) signed in June 2004 articulates the day-to-day roles and responsibilities of the signatories and documents the intentions of the parties to work cooperatively in partnership to deliver sustainable surface water management. It also recognises that G-MW is responsible for providing environmentally sustainable drainage services and that it works with its customers and partners to minimise the impact of drainage flows on beneficial use of downstream water. G-MW has obligations under section 39 of the Environment Protection Act (1970) to ensure that those industries that G-MW has entered into agreements with are aware that they must not in any way pollute any waters so that the condition of the waters is changed and makes or is reasonably expected to make those: - noxious or poisonous; - harmful or potentially harmful to the health, welfare, safety, property of human beings; - poisonous, harmful or potentially harmful to the animals, birds, wildlife, fish or other aquatic life; - poisonous, harmful or potentially harmful to plants or other vegetation; or - detrimental to any beneficial use made of those waters. Further to this, discharges from its channels and drains need to be managed to minimise the adverse environmental impact on the receiving surface waters through sediment, nutrient or other pollutant runoff, or by impacts of flow on the aquatic ecology (by altered flow regimes or channel erosion caused by flows) (clause 51 SEPP WoV). There are two broad categories of risk that G-MW is concerned with managing with respect to drainage. The first is the impact of the quantity and quality of drainage water on the receiving waterway, and secondly the impact of the quantity and quality of drainage water on G-MW s irrigation customers and drainage diverters. WATER QUALITY The various Acts and supporting legislation are not prescriptive in what the key drainage water quality parameters are that G-MW must monitor and/or seek to manage. From a regional river health perspective nutrients (phosphorous and nitrogen) and salt are the key elements that impact on sustainable aquatic environments. Phosphorus and nitrogen are two key nutrients in plant growth and are used extensively in agricultural systems. Excess phosphorous in the region s waterways has been linked to blue green algal blooms and nuisance weed growth. A key target of the 1997 Goulburn Broken Catchment Water Quality Strategy was the reduction of phosphorous entering waterways from irrigation drains by 50%. Salinity is still the driving water quality parameter in northern Victoria with salinity targets set for the River Murray at Morgan. G-MW has to keep an accurate record of the length of the drainage network and the area served by its drains and report annually to the Murray Darling Basin Authority (MDBA) on its contribution to salinity in the Murray. Salinity of drainage water is also the main water quality concern of drainage diversion customers. Suspended solids and turbidity are natural features of northern Victoria s lowland rivers and creeks. Drainage discharges can carry additional silt into the streams and 2 of 9

3 if not appropriately managed increase the rate of siltation and may smother invertebrate habitat and fill deep holes necessary for many native fish. In addition to these general water quality parameters toxicants such as heavy metals and hydrocarbons, and pathogens are of interest. Drainage water is only accepted where it enters the drain through an authorised connection. Most customers have at least one farm drainage inlet (FDI) through which they are able to provide off farm drainage to their properties. Many farms have multiple FDIs as a result of the topography and layout of their irrigation bays. The quality of irrigation drainage water entering waterways, particularly in relation to nutrients, is in most catchments driven by the quality of water leaving the irrigated farm. The average concentration of phosphorous and nitrogen in irrigation drainage water leaving farms is shown in Table 1. Table 1: TP and TN in runoff from different irrigated landuse Irrigated land use Concentration (mg/l) TP TN Perennial Pasture Annual Pasture Crops Vegetables Fruit The quality of irrigation drainage water has essentially set the benchmark around which G-MW considers the risk profile for other types of discharges. As part of programs with its catchment partners G-MW encourages the construction of farm drainage and reuse systems to minimise the runoff to its drains. It also encourages drainage diversion to reuse water from the drainage network, thereby reducing the volume of irrigation drainage water outfalling to waterways. The IDMOU mandates a process by which the Catchment Management Authorities and G-MW set water quality and management action targets for drainage catchments. The Resource Condition and Management Action Decision Support System (RCMADSS) is a 14 step semi-quantitative risk based approach to setting irrigation related water quality targets for receiving waterways (Green et al., 2008). Underlying the RCMADSS is an acknowledgement that in order to set realistic and achievable water quality targets consideration must be given to the type and number of management tools that can be applied to a catchment to bring about a positive change. The management actions identified and quantified through the RCMADSS seek to address the risk to the receiving waterway from general irrigation drainage inputs. Between 1997 and 2004 G-MW managed the risk to drainage water quality by requiring all non irrigation dischargers (urban and industrial) to its drains to enter into Drainage Discharge Agreements. This was a blanket approach which was onerous in its requirements. The drainage discharge agreements were to be applied to all new non-irrigation drainage connections and were not applied retrospectively. In 2003 G-MW and Goulburn Valley Water engaged in a process of assessing the risks associated with accepting runoff from properties irrigated with treated wastewater. With assistance from RMCG (Consultants for business, communities and environment), G-MW developed a risk based approach for the management of runoff from properties irrigated with reclaimed water. This progressed to a new 3 of 9

4 management policy and environmental guidelines to facilitate wastewater reuse and establish a framework for acceptance of urban and industrial water into G-MW drains. WASTEWATER / RECLAIMED WATER Across northern Victoria there are many towns and industries that have wastewater treatment plants of different sizes and levels of treatment. Government made a commitment that there would be a significant reduction in discharges of treated sewage to waterways and required urban water authorities to move to greater disposal through land based means. This sensible approach to management of reclaimed water in the northern irrigated region of Victoria often necessitated an increase in land area required for sustainable disposal. This is regularly achieved through third party properties supplied by agreement from the wastewater treatment authority. These third party properties are not licenced by the Environment Protection Authority (EPA) in the same way as the wastewater treatment plant and no specific approval is required for discharges from the farm. G-MW recognised that, for the most part, the quality of runoff leaving these properties would not be that much different to that from a property only irrigated with raw irrigation water. The slight increase in risk is premised on the differences in the quality of water being used for irrigation. Reclaimed water usually contains higher levels of nutrients, salt, toxicants and pathogens than the traditional water sources used for irrigation (RMCG, 2004). Accordingly, G-MW selected risk characterisations for the key water quality parameters around various agricultural input systems (see Table 2). Table 2: Risk categories for nutrients and salinity Category Very Low (VL) Low (L) Moderate (M) High (H) Extreme (EX) Description of Practices Conservative agriculture Common agriculture Acceptable high input agriculture Questionable agriculture, but theoretically possible To be avoided As part of the EPA reuse guidelines (EPA Publication 464.2) that cover the supply of reclaimed water to third party properties an Environmental Improvement Plan (EIP) must be prepared. The EIPs set out the management requirements, operational targets and monitoring/reporting requirements for a range of elements, including surface runoff. Using the process outlined in Figure 1, properties with an overall site risk of Moderate or lower are not required to enter into a drainage discharge agreement provided the reporting requirements are met and that there is no change in the overall site risk. 4 of 9

5 Existing/proposed waste water run off discharge to G-MW drain Australian and New Zealand Guidelines for Fresh and Marine Water Quality Toxicity risk factors and acceptance criteria toxicity issues? Toxicity risk low? Overall site risk for nutrients and salinity Risk levels very Low, Low or Moderate? Table 5 of this Guideline Waste generator/property owner to adhere to management practices in table 5 and produce annual report Drainage Discharge Agreement (see # for template) Waste water run off discharge to G-MW drain authorised Waste water run off discharge to G-MW drain not authorised Figure 1: Acceptance Process Flowchart for properties irrigated with reclaimed water (from G-MW Environmental Guideline 014) This process has been successfully applied to the properties supplied with reclaimed water from Goulburn Valley Water s Tatura Wastewater Treatment Facility. The four properties supplied with reclaimed water do not require a drainage discharge agreement and the monitoring and reporting requirements are no more than those required in each property s EIPs. Goulburn Valley Water assists the farmers in complying with G-MW s requirements by conducting the necessary tests and providing an annual report to G-MW. Salinity is the key risk factor for these sites due to the salt load from food processing on the treatment facility. 5 of 9

6 INDUSTRIAL Within the northern irrigation area of Victoria there are associated industries and businesses that support the agricultural production. Some of these industries are located outside of areas serviced by an urban authority s sewerage system and an alternative way of dealing with wastewater is necessary. An example of this would be the wash down water from a fruit packing shed. Acceptance of industrial discharges is handled differently to users of reclaimed water for irrigation. All other non-irrigation dischargers are required to meet G-MW s defined broad water quality acceptance criteria and enter into a drainage discharge agreement. Existing/proposed waste water discharge to G-MW drain General acceptance Criteria - Item 3 of this guideline Toxicity risk factors and acceptance criteria Australian and New Zealand Guidelines for Fresh and Marine Water Quality Drainage Discharge Agreement (see # & # for templates) Meets broad water quality acceptance criteria and, either there are no toxicity issues, or the toxicity risk is low? Discussions with waste generator/ property owner Waste water discharge authorised Can changes be made to meet Item 3 or to achieve low toxicity risk? Waste water discharge not authorised Figure 2: Assessment and Acceptance Flowchart for direct discharge of wastewater (from Environmental Guideline 013) For the example of cool store wash down water the drainage discharge would most likely be quite simple and essentially record that the connection to the G-MW drainage network is permitted and may specify the type of connection. Recently, the Shire of Campaspe has developed a greenfield site south of Echuca for a new regional saleyards, animal pound and waste recycling transfer station. This has been a staged development beginning with the saleyards then animal pound. The works are currently underway for the waste recycling transfer complex. The development is occurring on farm land that had a small water entitlement, was not 6 of 9

7 extensively irrigated and drained to a G-MW drain. G-MW has been involved in each stage of the development at the planning stage enabling the considerations around drainage discharge from the overall development to be discussed and incorporated into the works. The saleyards site covers the biggest portion of the development area and required consideration of potential effluent discharges as well as rainfall runoff from a large roof and car-park area. The saleyards uses soft floor covering system which is dry scraped and composted off site. Wastewater from the truck wash down bay is separated from general site runoff and directed to an effluent treatment pond. This effluent water is to be used on another part of the property for pasture irrigation. A drainage discharge agreement has been entered into by the Shire which specifies the size of retardation required on site, the way runoff from irrigation with effluent is to be intercepted and the monitoring and recording requirements and timeframes for review. As the overall development has progressed G-MW and the Shire have reviewed the drainage discharge agreement and considered any further conditions or change to the monitoring requirements. With the waste recycling transfer complex nearing completion, G-MW and the Shire will again review the drainage discharge agreement and its requirements. It is expected that the revised agreement will contain updated monitoring conditions and timeframe for review. The desired outcome is for the amount of monitoring and reporting to reduce after the first few years given satisfactory performance of the on-site detention and treatment process. URBAN GROWTH As regional centres like Shepparton, Mooroopna, Kyabram and Echuca continue to expand they move into areas served by G-MW drains. This pre-existing drainage infrastructure was designed to provide a service to a rural catchment and in most cases must continue to do so to rural properties upstream and downstream of urban development. Plenty of research has been carried out on the impacts of urban runoff on receiving waterways, particularly with regard to water quality, and the corresponding risk to the water quality in G-MW drains is fairly low. The risk to a compromised level of service to irrigation drainage customers is, however, high. The increase in impervious area as a result of urban expansion into rural catchments greatly increases both the volume and speed of runoff to the drainage network. G-MW s regional drains are generally built to provide either a 1 in 2 year, or 1 in 10 year level of service. That is, they are designed to remove within a defined period (usually 5 days) the runoff resulting from the design rainfall event falling uniformly over an irrigated catchment. This level of service is much less than that required for an urban drainage system, where water sitting on roads for five days following rainfall is not considered acceptable. Table 3: Drain level of service and maximum allowable discharge rate Drain Level of Service Max. allowable discharge rate (L/s/ha) 1 in 2 year in 10 year of 9

8 G-MW has adopted a range of 1 in 100 year design rainfall events for the determination of the required retardation capacity to restrict the urban development discharge to the design discharge rate for the drain. The increasing application of Water Sensitive Urban Design (WSUD) can allow designers to spread the required retardation volume throughout the development in swale drains and on-site wetlands. Gross pollutant traps and triple interceptor pits where likelihood of hydrocarbons is high are also recommended as part of WSUD to maximise water quality. Due to the low relief of much of the riverine plains most retardation basins must be pumped out following a rainfall event. The pumps must be sized according to the maximum allowable discharge rate in Table 3. To further ensure the level of service of the drain is not compromised the pumps must cut out when the water level in the drain rises above the pre-development ground level. Following the process outlined in Figure 2, a drainage discharge agreement is usually entered into with urban dischargers that specifies the size of the retardation volume required and the allowable discharge rate. G-MW encourages best practice stormwater management so that the general acceptance water quality criteria (Table 4) can be met and may require some testing of discharge events to check system performance. Table 4: Broad physio-chemical and microbiological criteria for determining acceptable quality for discharges to G-MW assets. Parameter Acceptance Criteria Suspended Solids 30 g/m 3 Salinity 1,200 µs/cm ph Total Phosphorous 2.0 g/m 3 Total Nitrogen 5.0 g/m 3 5 day Biochemical Oxygen Demand 40 g/m 3 Blue green algae Escherichia coli 1,000 cells/ml 150 organisms/100 ml CONCLUSIONS G-MW has sought to address the risks to and arising from owning and operating a regional drainage network through the strategic use of drainage discharge agreements and catchment programs with its partners. The IDMOU supports the mechanism through which irrigation drainage runoff water quality targets are set and details the broader roles and responsibilities of the partner agencies. Drainage discharge agreements are tailored to address the risks and management arrangements of the discharge type. Drainage discharge risk is generally assessed/considered in terms of its variance from expected water quality from irrigation drainage runoff. A single register of drainage discharge agreements is maintained as part of G-MW s Environmental Management System to assist in keeping the agreements reviewed and current. 8 of 9

9 This flexible approach to the need for and content of drainage discharge agreements minimises costs to the parties and reduces the amount of ongoing administration by only monitoring and reporting where necessary. REFERENCES Environment Protection Authority Victoria (2003a) State Environment Protection Policy (Waters of Victoria). Government Gazette. S107, 2003 Environment Protection Authority Victoria (2003b) Guidelines for Environmental Management Use of Water Reclaimed Water, EPA Victoria Publication Goulburn Broken Catchment and Land Protection Board (1997) Goulburn Broken Catchment Water Quality Strategy Addendum to Draft Strategy, June Goulburn-Murray Water (2006a) Acceptance of Urban and Industrial Water into G- MW Drains - Management Policy - 16 June 2006 Goulburn-Murray Water (2006b) Environmental Guideline 013 (# ) Wastewater direct discharge assessment and acceptance guideline January 2006, G-MW Goulburn-Murray Water (2006c) Environmental Guideline 014 (# ) Runoff to drain from properties irrigated with wastewater risk assessment and acceptance criteria guideline January 2006, G-MW Green S., Davies M. and Alexander P., (2008) IDMOU The key to better relationships and improved water quality target setting in northern Victoria Irrigation and Drainage Conference 2008, Irrigation Australia Ltd, Melbourne, Vic, Australia, May 2008 Hydro Environmental (2007) Management Action Assumptions Paper for the Goulburn Broken Catchment May 2007, GBCMA HydroTechnology (1995) Nutrients in Irrigation Drainage Water from the Goulburn and Broken Catchments Issues Paper.5, Goulburn Broken Water Quality Working Group Memorandum of Understanding for Irrigation Drainage Management and Water Quality June 2004 RMCG (2004) Management of Surface Run-off From Properties Irrigated with Reclaimed Water Risk Based Approach rationale and background information - February 2004, G-MW Victoria, Parliament. Water Act 1989, Version 092 Vicroria, Parliament. Environment Protection Act 1970, Version of 9