Leachate to Land
Last week we celebrated a proud environmental milestone following the completion of an important project in our #bigwastewaterstory programme when we commissioned our leachate to landfill irrigation project.
Check out one of our onsite signs for more detail;
The project initiated in 2011, has had a few stop starts over the years, but pleasingly we got there. The completion of the project ceases the tankering of landfill leachate to our wastewater treatment plants and implements a circular process whereby the leachate is stored onsite and irrigated back onto a completed and capped cell of the landfill at low rates.
Work is nearing completion and by the end of the week, the project should be commissioned, and only general site tidy up and fencing to be completed. On track for the revised opening on the 7th of October 2021.
The recent COVID-19 Level 4 lockdown unfortunately slowed down our planned completion by the end of August 2021, the team has recommenced on site under Level 3 protocols. Work remaining is the concrete pad, pump station installation and our fencing planned for around the pond.
The team is currently working on installing a weir to measure the amount of discharge through the subsoil drain that clears the groundwater under the new leachate pond.
Grass is starting to strike around the pond, and once is better developed - the new fence around the pond will be constructed.
A new date for completion and opening is the first week of October 2021.
We continue to make good progress with the leachate project and the pond is now lined thanks to some good weather a few weeks back, we commence work on reinstating the works area around the pond, works are planned to complete the pour of the concrete pad for the pump by middle of next week, allowing the control unit and pump to be installed in a couple weeks, the project is 75% complete, and work is on track for the opening and commissioning on the 26th August.
The pond is now complete, and the clay lining has passed the densometer testing, some further drying is required and the geotextile and PE liner can be installed.
The pipework is installed within the irrigation area awaiting the irrigation pods to be installed.
Work is progressing all of the underground power and irrigation is now installed, next week will see further import of clay to complete lining of the pond prior to lining.
Work is progressing well, and our contractor has emptied the pond of the remaining stormwater, stripped the pond back and made a number of subsoil connections to the drain. Additional clay is being brought into to site to complete the leachate pond prior to lining.
Council has awarded Stage 2 of these works to Higgins to complete the leachate collection pond and the irrigation system including pipeline, pump station and irrigation pods.
It is anticipated works will be completed by the end of June 2021 and commissioning will take place in July 2021.
Unfortunately Stringfellows are not able to return to site in the near future due to existing regional projects meaning they are unable to resource the Stage 2 works. Council will be procuring a contractor to complete the Stage 2 works.
Council is working with the incumbent contractor Stringfellows who undertook Stage 1 works (commencement of leachate pond construction, subsoil drainage, build of irrigation cell and grassing) to return to site to complete the remaining works known as Stage 2.
Council has been granted a short term (3 year) resource consent to discharge the groundwater collected in the subsoil drain to the nearby farm pond. The short term consent is to allow sampling to be undertaken to understand the effect of the discharge on the surrounding environment.
We have provided further information to support the consent application regarding an assessment of effects of the discharge on the receiving surface water body and aquatic life.
We have provided further information to support the consent application regarding the general groundwater flow direction and additional groundwater quality samples.
We have lodged a resource consent application to allow the discharge of groundwater from the subsoil drain under the leachate pond to the nearby farm drain.
Works have been paused while we gain this resource consent.
This is due to the risk of lining the new leachate pond while their may be presence of water putting pressure on the liner, which may result in the liner perforating (ripping). We cannot complete the lining until we are able to relieve the subsoil collected water.
2020 work will continue on finishing the leachate pond, pump station and pipeline.
Work is also underway to gain a resource consent to discharge groundwater to a local stream. this will alleviate any pressure build up underneath the liner of the leachate pond.
The cap is all but complete to irrigate the leachate onto.
Unfortunately due to water in the pond, and issues with groundwater levels and ability to safely discharge the lining works have been postponed.
The cap is progressing well and is nearing completion.
The team have been doing well juggling the many aspects of this project. With a focus being on sourcing the right clay and relocating the dry sludge from the landfill to fill a void at the landfill, with a third of the dry sludge (approx. 1500 tonnes) carted to the landfill the void is now ready to have mudstone layer applied and then a topsoil layer to allow it to be irrigated onto.
The new leachate pond is also on track to be lined from Mon 25th November, focus then shifts to the new pipeline and pump station.
The void is filling up well as we blend waste and sludge.
We are now also doing some work filling the void at the landfill that we will irrigate onto, this is a great opportunity to fill the void with sludge from the wastewater pond that has been drying for many years.
This saves cost as we dont have to import clay or waste.
Below is a photo from Waipawa geobag drying area.
We have had a lot of rain and this has impacted our pond that was drying nicely, we now need to focus on draining the pond to again allow it to drain and to reduce the moisture content.
The pond is taking good shape now, and is nearly ready to be lined.
We are now investigating a borrow site at the back of the landfill that will be used as final cover to shape the capped area on the landfill where the leachate will be irrigated onto. This is important in getting the right type of fill to ensure the permeability is correct for irrigation.
The pond has largely taken shape and is now being prepared for lining.
Update - 01 October 2019
The team has now shifted to excavating the new trench for the stormwater line that will provide the subsoil drainage.
The pond is taking shape and Stringfellows are working through creating the batters and gradients in preparation for inspection.
Stringfellows are currently excavating around the old leachate pond and continuing to create the new pond shape.
Earthworks on the new leachate pond is progressing well as our contractor Stringfellows currently forms the new pond shape.
Work is progressing well - glass has been shifted to a new bunker, and the team now start earthworks and creating the leachate pond.
Last week council endorsed a report to approve the additional budget required to complete this project, this week the start-up meeting takes place, and the contractor starts establishing site, the project involves shifting all the glass stored at the landfill away from the project site to a purpose built bunker (this glass is stored to be used in future as basecourse for any new cells), a large leachate pond is to be created, along with a new pump station and pipeline through to an irrigation area where new irrigation pods will be installed to irrigate the leachate onto a capped cell area of approx. 1.2ha.
Council has completed a robust procurement process and has identified a preferred supplier for this project.
Council now works to seek the relevant approvals, and is in the planning stages with the contractor and the landfill operations contractor to progress this project.
Works are expected to commence in late Aug 2019.
A resource consent has been submitted to Hawke's Bay Regional Council to amend the current resource consent conditions to allow us to irrigate the leachate back onto the landfill.
Following granting of consent conditions, Council plans to take this project to the market to identify a suitable partner to undertake the proposed works.
Below is an overview of the proposed irrigation area.
Three options regarding storage for the leachate project have been presented, CHBDC have reviewed the options and agreed to proceed with an option to increase the pond storage currently in-situ on the landfill. At present CHBDC are preparing a resource consent application to allow for this change in consent on how we manage the leachate. CHBDC expect to have lodged the consent with HBRC by mid March 2019.
CHBDC commissioned a survey of the landfill to help better understand the topographic and levels to progress improvements at the landfill and inform the leachate project requirements, in particular the surface area required to irrigate the leachate on. Below is a snapshot of the survey image.
Council has re-commenced a project that was conceived in 2011, to eliminate tankering the leachate produced at the landfill to the wastewater treatment pond in Waipukurau, and to instead create a circular system where the leachate is captured and irrigated back onto a completed area/ phase of the landfill.
This holds benefit for the wastewater treatment process - as leachate can be high in ammonia.
The project once completed is expected to reduce operational costs as well as better our environmental and carbon footprint through reduced emissions from tankering the leachate numerous times a day.
The project is in the early stages, design is to be completed and then a contractor procured to deliver this project.
Council hopes to have a system up and running in early 2020.
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