This paper looks at two bank stabilisation projects and a treatment wetland project to demonstrate the benefits and challenges of integrating nature into engineered stormwater solutions.
This paper outlines our reflections on the experience of disseminating flood hazard information, the challenges encountered and the resulting process proposed for communication utilising the lessons learnt from the release of flood hazard information for the Mangaroa and Wainuiomata Rivers.
This paper will describe the regional planning framework’s development, discuss the planning initiatives used by the ECan expedite district councils to prepare stormwater management plans (SMPs) and catchment/network discharge consent applications. Also discussed will be the specific issues relating to SMP’s and catchment / network stormwater consents granted in the Canterbury region to date.
Te Whariki is a joint venture Ngai Tahu Property and Lincoln University residential development in Lincoln, Canterbury. This transition of a greenfield site into extensive urban development includes the use of constructed wetlands which have shown improving stormwater treatment efficiencies.
Atmospheric deposition is increasingly being recognised as a significant source of total suspended solids (TSS) and heavy metals in urban runoff. However, many uncertainties and challenges remain with measuring and managing these pollutants in runoff. Impermeable concrete boards were deployed in a residential, industrial, and airside landuse area in Christchurch for almost one year in 2013 to determine the spatial and temporal variability of airborne pollutant loads (principally TSS, Cu, Pb, and Zn) in runoff.
A challenge that faces all stormwater network managers is finding the appropriate balance between good environmental outcomes and cost effective solutions. The resource consent process can lead to controls being placed on discharges through consent conditions that limit flexibility, does not provide for advancement in knowledge, or limits consent duration.
The paper presents key learnings including: soil container construction, advantages and disadvantages of the three bank re-grading options used, potential for community construction initiatives, construction of fish refuge habitats, woody weirs and log overhangs, and effects of sedimentation on those features. The performance of the stream bank erosion mat product used and associated variable vegetation uptake on the stream banks is also discussed. A design calculation method for anchored woody instream structures is also presented.
This paper describes the objectives, site constraints, tight timeframes, options considered, stormwater solution designed and constructed and the lessons learnt for the new Business Park and existing Airport landside development.
This paper outlines some of the lessons learnt regarding managing flooding in England, such as understanding the full costs of land use planning decisions, planning tools used in England, and the importance of defining terms such as ‘safe’ with respective to flooding. Although there are some marked differences in both catchments and development pressures between New Zealand and England, this paper also considers how this knowledge and some of the lessons could be applied in the local context.
Rain gardens are Water Sensitive Design devices that use bioretention to retain, and reduce pollutants in, stormwater runoff. Resilient rain gardens consistently attenuate pollutants, volume, and peak flows from small rain events. Research projects investigated combinations of readily available materials in the Auckland region that have consistent physical and chemical properties suitable for bioretention. The mulch and filter (or fill) media used influence rain garden performance – mulches must not float and must have high permeability.
Conventionally biogas production and renewable energy generation utilising digestion at wastewater treatment plants (WWTPs) has only been considered cost effective at a large scale, unless the facilities have pre-existing digesters and primary sedimentation tanks. The perception is that small WWTPs (less than 20 MLD) - are limited in opportunities for beneficial biogas and renewable energy generation. This view has arisen from two key factors: Small facilities have limited sludge volume which typically means low gas production, and; the capital cost associated with installation of new infrastructure is proportionally high, meaning these facilities are not cost-effective at a small scale.
Currently, landfilling of biosolids is practiced by the majority of local authorities due to perceived and real uncertainties around social and cultural acceptability and risk of alternative disposal methods. There is a strong scientific case that application to land is a sustainable option, because biosolids are carbon-rich and contain high concentrations of valuable nutrients that can be used to bolster soil carbon reserves, thereby reducing dependence on artificial fertilisers. However, this approach is also potentially the least acceptable to the New Zealand public.
Prior to the 2010 and 2011 Christchurch earthquakes, microbial water quality measurements of the Avon River intermittently exceeded recreational water quality guidelines. The 2011 earthquakes resulted in direct sewage discharges to the Avon River of more than 5,000 cubic meters a day over six months.
Globally there has been a paradigm shift from disposal to resource recovery of biosolids. The K?piti Coast District Council is in a favourable position to be a leader with municipal biosolids beneficial use in New Zealand. This is due to high quality Grade ‘A’ equivalent biosolids being produced from its sludge treatment systems which allow various beneficial use options to be a possibility.
The Wairakei geothermal power station situated in Taupo in the North Island of New Zealand was commissioned in 1958. Condensing water and geothermal steam condensate containing hydrogen sulphide is discharged to the Waikato River.
Aeration in Wastewater Treatment Plants (WWTP) is typically undertaken via diffused aeration systems (membrane or ceramic diffusers and aeration blowers). Operational costs for aeration are typically 30-40% of total plant OPEX and 50-70% of the electricity consumption in an activated sludge process.
The Paraparaumu Wastewater Treatment Plant uses a thermal sludge drying process to produce a Grade ‘A’ stabilised biosolids. This treatment plant previously used a diesel boiler which provided heat via a high pressure hot water circuit to a rotary drum dryer.
This paper considers how the attributes of existing properties can impact upon the preferred reticulation technology through cost, risk and practicality. A methodology is presented to facilitate the quantitative assessment of each individual property in the catchment and how this assessment can be used to optimise the selection of the final wastewater reticulation technology and network configuration.
This paper describes the investigation and planning phase, optioneering, risk analysis and early involvement with specialist pipe rehabilitation contractors which resulted in an alternative approach. This approach resulted in the trunk main itself being rehabilitated using Cured in Place Pipe (CIPP) liner.
The paper discusses both the design and construction stages of the projects including pros and cons of directional drilling technology for the pressure main, pipe welding, pipe testing, inlet design of the pump station, wet well hydraulics, proper pump selection to minimise wear and tear, odour treatment and ground improvement strategy to mitigate seismic-related damage and construction issues.
This paper will describe the differences in BDOC concentration in relation to the backwashing frequency of the BAC filters, water temperature, initial dissolved organic carbon (DOC) levels, ozone residuals and temperature of the BDOC test itself in the water collected from Orange WTP over the year 2012.