More than 700 days have lapsed since stage two of Carterton's wastewater treatment plant was originally due to be completed.
And the reasons why have been given in a project update set to be discussed by councillors on Wednesday.
In Carterton District Council's 2015-2015 long-term plan, a budget of $2.75 million was included for the majority of the stage one work and for stage two of the project.
The project evolved, and the most recently published budget for stage two is about $5m.
This budget has blown out by $435,550, a council document shows.
Despite this, the wastewater treatment plant's construction total still falls within the project's $12m budget stated in the document.
The document, authored by council chief executive Jane Davis, states five issues have impacted stage two of the project, including the relocation of mudfish from the Daleton Farm site, contractor time delays, Covid-19 time delays, unsuitable material and additional drainage works, and ephemeral channel relocation.
The second stage of the project was initially set to be completed by May 30, 2019, but it is still ongoing.
The latest completion date given is "early June" this year.
The first stumbling block for the project was when 921 mudfish, an endangered species, needed to be relocated from drains on Carterton's Daleton Farm in late 2018 as a condition of the project's resource consent.
Just shy of $350,000 was spent in the relocation; costs to ratepayers included $160,305 for ecologists [$60,000 was budgeted], $49,000 for drain recreation, and $132,862 in claims by the project contractor Central Hawke's Bay Earthmovers.
Very few mudfish survived the exercise.
Other issues identified by Davis were "unforeseen conditions on the farm", requiring the removal and replacement of 62,150 cubic metres of fill within the footprint of the new reservoirs.
This was despite detailed geological investigations completed in mid-2016 by Tonkin and Taylor and the council's first project team.
Davis said in the document that CHB's speed to remove the material was "significantly less" than the rate it included in its tender.
The company was awarded a two-month time extension.
The document states that while CHB's "slow productivity has caused major time delays", costs were still lower than alternative tenders.
CHB's costs for this stage of the project were $1.6m, and the next lowest tenderer was nearly $2.7m.
Davis cites "CHB's poor contract performance" for about 12 months of delays.
Other delays were attributed to unforeseen elements including bad weather and Covid-19.
The CHB delays caused significant project supervision costs; initial costs of supervision were forecasted at $136,000 to June 2019.
"However, two years on, costs are forecasted to be $550,000 to June 2021," Davis said.
"Under the general conditions of the contract, there is a provision for time-related damages [against CHB] of $6460 per week to cover this additional cost."
The Carterton wastewater treatment plant project is not yet completed but is still within the time period of consents to have the reservoirs working.
Once the works are done, the plant will be commissioned.
Davis has recommended a full independent review of the project to identify any "shortfalls on the council's part … and any lessons we can learn for future projects".
The project update document and a review will be discussed by members of the council's audit and risk committee on Wednesday.