Ōtaki Forks temporary walking access and Blue Bluff road reinstatement

Update 30 January 2025

• A press release 28  January from KCDC gives some additional information on the Blue Bluff earthworks, but does not give an actual start date.


• A contract has been awarded for the earthworks but the contractor cannot begin work until a Resource Consent is issued, and KCDC cannot give a date for this.


• As at 30 January the contractor is not on site and the track through the slip remains open. But presumably work will begin immediately a Consent has been issued by the KCDC and the slip track will then be closed and the only access to Otaki Forks will be via the DOC track—but that could be tomorrow, next week, whenever.


• If you are planning a trip to Otaki Forks plan accordingly!?

Update 18 December 2024

• As at July 2022 there is a KCDC formed walking track directly over the Blue Bluff slip. To get to this track simply continue along the road past the orange triangle and sign directing you through the gate. This is well used in spite of warning signs and saves a very significant amount of time and effort over the DOC route. Here is a video of the Blue Bluff track


• In May 2024 Kapiti Coast District Council made a decision to reopen the road, at a cost of $7.5 million subject to available finance. In December 2024 KCDC approved the finance for the work which should start late January 2025 and take between 4 and 6 months to complete.


• This means that during the construction phase the Blue Bluff track will not be available and a temporary higher-level walking access track will again be necessary – possibly this existing one but DOC is yet to confirm the route.


• But sometime about June 2025 vehicle access to Ōtaki Forks should be fully restored. Great for all the Ōtaki Forks visitors – trampers, holiday campers, picnickers, day-walkers, paddlers – and those living past the slip.

KCDC Option A – Open the Road

6        There are two slips which require repair, the under slip and the over slip.

7        Feedback from the community received to date is that vehicle access to the Otaki Forks campground is the most desired option. This provides a level of accessibility for all of the community, especially families, to experience the Tararua Ranges and campground facilities.

8        We recently met onsite with representatives from an earthmoving company experienced in working on complex slip faces to discuss constructability, especially with regards to safety.  After viewing the site they advised they believe they could complete the earthworks to repair both slips within 4-6 months and did not have any specific concerns regarding safety. Their methodology involves:

8.1    Cutting the northern end of the 2016 bottom bench to allow digger and truck access past the under slip to the northern end of the over slip.

8.2    Removing the slip face of the over slip, working up the slip from the road in sections, battering at approx. 1:1 ratio.

8.3    After reinstating the road, safety mesh and / or a rockfall catch fence would be installed.

8.4    Complete realignment of the road above the under slip, by benching back into the 2016 repairs. This is seen as a straightforward process with little risk.

9        This construction methodology for the over slip satisfies Council officers concerns regarding safety as the process minimises risk of slippage and provides an identified escape route for the contractor during construction.  It is to be noted the site contains unknowns and at any point the works may need to stop if safety concerns are raised. 

10      The methodology is also cost effective for Council as it deals with the area with the most uncertainty first, e.g. the over slip and uncertainty regarding the roads existing retaining wall. Using this methodology, we are able to refine the upper limit of expected costs and hold the project should the existing road retaining wall present issues.

11      Following repairs to the over slip, and while the under slip road is being realigned, we can complete repairs to the road corridor from just beyond the over slip to the DOC camp site.  This includes safety repairs to the Pukeatua bridge barriers (bringing up to code), repair of minor under slip near Pukeatua bridge and replacement of 3 stormwater culverts.  Estimated construction is 1-2 months and can be completed any time after the over slip works are completed.

12      The immediate vicinity of the over slip site is part of a larger older landslide that has since healed and re-vegetated with no obvious signs from aerial imagery that it deteriorating further upslope of the road to the south. It is unknown when this landslide initially occurred, however available aerial photography indicates it was prior to 1948.  The historical landslide site is approximately 97,000m2 and has since progressed through cycles of small/moderately sized active landslides which form and then heal.

13      Around 1981 the Otaki Gorge Road was realigned (assuming this was due to the developing loss of land from underslips at Blue Bluff) with the formation of benches cut on the northern hillslope above the road (excavation method to form a series of horizontal steps – this is to protect workers from cave-ins.) Around 2003 an overslip in the area of blue bluff was cleared and the road realigned again. The 2015 blue bluff slip was cleared and the benches recut in the current formation. The 2020 underslip and 2021 overslip are yet to be resolved.

14      No one can predict when the next landslide will occur, however based on historical evidence of 4 significant slips since 1981, we could expect return period of 10 years for similar events into the future.

15      Known slips:

16      The 2015 slip repair was cut into stable material (fractured greywacke) and is performing well. We would be able to cut a similar formation for the 2020 underslip repair and expect similar performance. It is unlikely that similar material will be found in the 2021 overslip area, however the head of the slope has a good shape and moderate stability should be able to be achieved by removing the overburden.

17      The further south we go along the historical slip scar the size of historical slips are smaller and have been able to be managed by general slip removal and retaining walls.  While a large event is possible, the return period is expected to be longer.

18      Acquisition of private property is required to realign the road, and potentially allow access for construction / earthworks and material disposal.

19      ESTIMATED COST to Council is $2.235m

20      We estimate an ongoing cost to Council for repairs to large slips is potentially $1,000,000 every ten years, with current Waka Kotahi subsidy levels; plus annual cost of $75,000 for ongoing maintenance of the road corridor.

21      PROS access is restored to Kapiti’s main entrance to the Tararua’s, and DOC’s Otaki forks campsite and properties located beyond the slip. Likely the quickest solution.

22      CONS condition of road retaining wall located under the over slip is unknown, risk of further slips occurring in the future.