Stormwater consent for northeast Levin finally granted: Work under way

Work has started on the Coley Pond.

Work has begun on a sediment pond and wetland treatment system on the corner of Fairfield and Roslyn Rds in Levin, known as the Coley Pond. The area feeds stormwater into a tributary connected to the Koputaroa Stream and has been under considerable pressure in the past few years in times of heavy rainfall.

The earthworks started this month and will hopefully put an end to flooding in Levin and further downstream.

Northeast Levin has a history of flooding during times of heavy rainfall and increased building activity upstream is making this worse.

Work has started on developing sediment ponds on the corner of Fairfield and Roslyn Roads.

Horowhenua District Council has been working for years to alleviate the problem but was stymied by a very slow-moving resource consent process for stormwater discharge in that area, which began as long ago as 2015.

Pumps were installed on Okarito Ave and Kennedy Drive to help deal with the flow of stormwater since then and larger pipes were installed along Fairfield Rd.

By 2017 the pipe and culvert under the intersection with Roslyn Rd were replaced by bigger ones to cope in extreme weather events, reducing runoff going over land.

Given the amount of work involved a resource consent was required and the process of talking to iwi and landowners began with the application was lodged with Horizons in 2017.

In 2018 Horizons requested more information. It was publicly notified in September 2019.

The resource consent was finally granted late 2021.

The extent of the stormwater flow across the Coley Pond.

Greg Bevin, Horizons Regional Council regulatory manager, explains the reasons behind the lengthy process.

"The delay between lodgement and public notification was due to further information being requested from the applicant. The hearing was held in November 2021, with consent issued by the hearing commissioner in December 2021.

"The delay between notification and the hearing and subsequent decision, was due to consultation between the applicant and submitters, changes to the design of the stormwater attenuation system by the applicant and further information required around a number of environmental effects," Bevin said.

For a very long time a so-called penstock has been in place over the enlarged stormwater drain below Roslyn Rd. That was to prevent too much water going down the drain, resulting in water building up front of it in times of heavy rainfall.

The resource consent was needed to "only for the discharge to water of stormwater and the construction of the stormwater attenuation ponds. The only requirement in relation to the pipes (original or upgraded) was that discharged stormwater from them remained the same rate until the new consent was issued," Bevin said.

The penstock, a wooden board, that helps limit the flow of stormwater down the enlarged drain. Once the Coley pond is installed is can be removed now the resource consent has been granted.

Horowhenua council infrastructure general manager Brent Maguire confirmed this. Hence the penstock.

"The timber board penstock is not part of the consent. It was put in by HDC to temporarily restrict flows while the consent was being resolved. Once the Coley Pond has been constructed the boards will be removed and water will be conveyed through the new purpose-built facility."

The facility is being constructed by Higgins at a cost of $2,678,910, according to tender papers, lodged in November 2020.

According to a recent council agenda, the consent allows for the detention of any potential increase in stormwater within the unnamed tributary of the Koputaroa Stream via a series of three embankments and attenuation ponding areas.

"The first stage of works involves construction of a coarse sediment settlement bay and wetland treatment system on council-owned land at 124 Fairfield Rd (otherwise known as Coley Pond). The Coley Pond attenuation area will not be permanently wet and there is currently negligible freshwater or riparian habitat of any value.

Work has started on the Coley Pond.

"The second and third attenuation ponds are not required for the current housing development phase as hydraulic neutrality is achieved with the construction of Coley pond. The consent allows Council to construct these ponds no later than within 12 months of 350 new lot titles being created in the north-east Levin development area."

Bulk earthworks are expected to take two to three months, depending on weather.