Te Marua, Upper Hutt

The New Zealand Transport Agency is undertaking erosion control works to repair and protect the Hutt River bank beside State Highway 2 south of Te Marua Golf Course. Successive storms and the November 2016 earthquake have caused parts of the riverbank to collapse. The Rimutaka Cycle Trail runs along the bank and is currently closed to pedestrians and cyclists in this spot due to safety concerns.Emergency stabilising work began in early April following slips caused by heavy rainfall and protected the state highway until a permanent solution could be put in place. From late April, a project has begun in which a wall of interlocking rocks will be constructed as permanent protection for the riverbank, highway and cycle trail from further erosion.

The construction phase is expected to take up to six weeks through May into June 2017 and follows approvals from the Greater Wellington Regional Council and Upper Hutt City Council. The works will take place during the day from 8.30am-3.30pm Monday to Friday.

Impact on trafficThis is a busy stretch of highway, particularly during commuter traffic morning and late afternoon. Travellers became accustomed during April to stopping to let trucks enter and exit the emergency stabilisation works site and to driving to a temporary speed restriction through the area.

The normal speed limit of 80kph through Te Marua has now been reinstated. Through May into June, drivers should expect on occasions to come up behind a traffic control truck with an electronic sign which will hold back the traffic for a few minutes to let works trucks through.

Protecting the riverbank at Te Marua

HUTT RIVER

Te Marua Golf Course

Location of collapsed bank

FLOW

Te Marua, Upper Hutt

Impact on neighboursThis work is important for the safety of people using the highway, the cycle and pedestrian trail and for your community. Neighbours of the work site will notice some noise and vibration from machinery during the day, including the sound of large rocks being off-loaded and placed on the riverbank. The worksite will be closed to the general public by gates at the entrance.

Our workers will become a familiar presence in the community, with a regular crew of six or seven people on site as well as truck drivers coming in and out. Four utes used by the construction workers will park on Beechwood Road during the project.

For those living near the worksite, access to your properties will not be affected. Local residents travelling from their homes onto the highway will notice traffic travelling slower than usual during the daytime and should allow extra time to reach their destinations.

Top, the collapsed cycle and pedestrian trail after slips from March 2017 flooding.

Bottom, the temporary trail behind the safety barrier, looking north.

Te Marua, Upper Hutt

Impact on cyclists and pedestriansThe Transport Agency is committed to restoring this important section of the cycle and pedestrian trail which forms part of the New Zealand Cycle Trail. The trail will be reinstated after the works are completed.

In the meantime, there is a temporary path on the road shoulder behind the safety barrier. During the working day while the work site is in use and trucks are entering and exiting, our personnel will escort cyclists and walkers from one side of the site to the other. At all other times, you will be able to walk past unescorted to rejoin the trail on the other side.

Hutt River and State Highway 2 at Te MaruaThe state highway lies adjacent to a sharp bend in the Hutt River just downstream from Te Marua Golf Course and the junction of the Hutt and Mangaroa Rivers. The highway is on an embankment and is about 7 metres above the level of the river water in dry conditions. The Rimutaka Cycle Trail is about two-thirds of the way up the river bank.

Due to the sharp change in the river’s direction of flow, the bank has been progressively eroded below the state highway. A 70-metre section of riverbank has undergone numerous slips and now needs permanent stabilisation with a rock wall.

What’s happening?A rock wall known as a riprap wall will be constructed over a riverbank that has been backfilled, covered with geotextile cloth that filters water through and overlaid with gravel compacted as a base. Riprap means layers of large rocks laid carefully to form an interlocking mass as a strong barrier against floodwater. The angle (or batter) of the wall and the slope up the bank will not be steep but will lean back gradually to prevent the wall from slumping.

About 3000 tonnes of large rocks of will be delivered early in the construction period at a rate of 20 truckloads per day and each load will be stockpiled on site according to its weight and mass. A 20-tonne excavator with bucket will lay the rocks in place. The works track along the riverbank has been upgraded to handle the weight of the trucks and is closed with a large gate out of hours.

Works: • Temporarily realigning the river flow away

from the wall construction site to allow the placement of compacted gravel and riprap rocks at the toe of the bank. This involves dredging a channel through the gravel spit in the centre of the river.

• Constructing a temporary bund (mound) from river gravel connecting to a river spit for access to the work site.

• Backfilling the riverbank and constructing the riprap rock wall to protect the 70-metre stretch of riverbank that has been eroded.

• Building a reinforced earth retaining wall for the cycle trail and slope adjacent to the highway.

On completion of the riverbank works, Capital Journeys will restore the cycle trail and install a new guardrail beside the highway.

Rocks for use in the riprap wall.

Constructing the bund.

And finally…please let us know how we didOnce this work is finished we’d really like your feedback on how you feel it went. You can fill in a survey online at www.surveymonkey.com/nzta-feedback or simply email us your comments on info@nzta.govt.nz

Te Marua, Upper Hutt

Thank you from the Transport AgencyOn behalf of the Transport Agency, thank you in advance for your patience and understanding while we do this important work in your community. The work is being carried out by the Capital Journeys joint venture of Opus Consultants and Fulton Hogan.

Keeping you informedStay up to date with this and other highway projects at www.nzta.govt.nz/wellington-maintenance or information broadcast throughout the day on major Wellington radio stations.

For more information, email customer@capitaljourneys.co.nz or contact: NZ Transport Agency Project Manager Dandan (Grace) Huang, dandan.huang@nzta.govt.nz, 021 830 012 or Capital Journeys Project Manager Glen Loveridge, glen.loveridge@fultonhogan.com, 0272 727 355.

For daily information on what’s happening with traffic on the roads, follow NZTA Wellington on Twitter and Facebook.

March 2017 photo showing the erosion close to the highway before emergency

stabilisation work was done.