We're paying for reckless repairs
Erosion protection for the pathway at Hardinge Rd is under way which will please local residents. The contract was awarded to the HBRC which owns the port company responsible for the damage, however, the Napier ratepayer is required to fund repairs. What should have been cheap maintenance of simple shoreline protection has turned into a very expensive remedial project.
During the 1970s, vast quantities of rock rubble were removed from the in-shore for retaining reclamation at the port. Hindsight and recent erosion could question the wisdom of this exercise. Also, countless truckloads of sand and gravel were carted from Perfume Point.
This site was a renewable source of cheap filling which would otherwise accumulate and overflow across the channel and deposit on Westshore Beach.
The shingle pit was closed around 1980 because accretion had ceased. At the time, nobody connected starvation of beach replenishment and port development. These events were not a mere coincidence.
Over 80 reports by engineers agree on the cause of erosion at Hardinge Rd, with the exception of the Komar Report which omitted or disregarded crucial factors. These undisclosed interruptions to coastal sediment are detailed in my Erosion Assessment 2009.
The length of seawall repairs extend 45m and involve filter cloth, crushed concrete, limestone rubble and a 1.5m layer of limestone boulders costing $135,000. This is over designed and extravagant expenditure. Even though retaining beach sand is not an issue, the 2 to 1 slope of the seaward face will make beach access difficult and wave backwash will increase. If this seawall, at $3000/m is adopted for the remaining 900m between Macauley St and Ahuriri Lane, then the whole project at $2.5 million will be an inexcusable waste of ratepayer funds.
In my opinion, a simple "rip rap" seawall with a base of graded rubble and a rock armour layer with varied sizes to 1m diameter at a 1 to 3 slope would be quite adequate. The current seawall was constructed by direct dumping without the benefit of hydraulic diggers to place rock. During the past 80 years, shoreline protection has worked exceptionally well but unfortunately, nobody took responsibility for repairs and maintenance.
A simple top up with quarry run limestone by a skilled operator could suffice for another 80 years.
Engineering consultants consistently report the breakwater is the principle cause of erosion at two Napier beaches. Recent extensions to the breakwater deflect shingle to deeper water but the main cause is the shipping channel collecting the sand and gravel. Depth soundings confirm this conclusion, however, the port company and the HBRC successfully exonerated themselves with the uncanny assistance of an overseas expert. Unfortunately, Mayor Arnott and her councillors unwittingly accepted a pre-existing problem and a massive burden for ratepayers. An exception was former Councillor John Harrison who did the research but still could not get his colleagues to support him.
The port has developed superb facilities and it is vital the navigation channel is regularly cleared of built-up sand and deepened to handle larger ships but adjacent beaches have suffered. It is obvious channel dredging has to continue but the full cost to repair and make good should fairly rest with the port company.
Hardinge Road residents have successfully pressured the NCC to save a section of concrete pathway. At Westshore, the pathway is not under threat but the sandy beach has been destroyed and the reserve continues to retreat. The NCC recognised the problem in 1980 yet a solution is nowhere in sight. I have presented comprehensive engineering evidence but both councils will not discuss or answer questions. This council has completely failed Westshore Beach - any suggestions?
Larry Dallimore, Westshore