Revealed: The beaches failing the safety test
Most of the Nelson region's popular beaches and swimming spots are safe to use but some remain prone to faecal contamination, the latest water quality monitoring surveys reveal.
Sampling over last summer shows that bacteria levels exceeded national guidelines 12 per cent of the time at eight sites monitored by the Tasman District council, reaching alarm levels on 12 occasions or half the time, mostly after heavy rain.
It was a similar story at the 10 Nelson City Council sites monitored, where guidelines were exceeded 13 per cent of the time, with half (14) of these samples being above alarm level. Exceedances were up slightly on the previous summer.
In a report to the TDC, resources scientist Trevor James said compliance with the guidelines remained high at 97 per cent during normal conditions, which was similar to previous years.
However, he identified several areas of concern which included:
Tukurua Stream at the camp playground continues to record regular elevated levels of faecal bacteria which exceeded guidelines eight times over summer, prompting warning signs to put up again in February after being taken down earlier in the season.
Samples of freshwater that had ponded after heavy rain in the main recreation areas at Rabbit Island showed bacteria at alarm levels and to be from humans. Although the concentrations dropped below guidelines within four days, they posed a significant risk to health. Further monitoring was required to determine if the pollution came from the public toilets on the reserve or from the discharge of biosolids on nearby forestry land.
The presence of the highly toxic algae, cyanobacteria, exceeded guidelines in the Waimea River and lower Wai-iti River for all but a few weeks from late November through to mid April. It was believed to be responsible for the death of three dogs and also posed a reasonable risk to toddlers who had a habit of eating things as a way of exploring their environment.
Even small floods in the Motueka River and coastal streams were found to cause bacteria levels to breach guidelines at beaches at Stephens Bay and Kaiteriteri.
Water quality was very poor after rainfall at all sites monitored in the Buller River catchment, but was not as bad as in other intensively farmed areas in the district. Bacteria levels returned to normal within a couple of days, but with the river being popular with recreational users, the council had an obligation to try to reduce peak loads and the time it took to be safe to use again, Mr James said.
TDC environment information manager Rob Smith said that apart an ongoing baffling problem at Tukurua, the district's most popular swimming places were not getting any less safe.
However, people wherever they were should avoid getting in the water immediately after heavy rain, particularly if it was discoloured, because of the risk of harmful bacteria from land run-off and stormwater.
The public health risks were not high enough to justify the huge cost involved in the council increasing its weekly summer monitoring regime, which involved taking samples from six core sites one year and then from 23 sites the next year. It currently spends $13,000 a year on a programme that was approved by the Nelson Marlborough District Health Board which had to be consulted over what action to take in the event of high bacteria counts.
The source of bacteria at Tukurua remained a mystery despite upgrades to private sewers and improved farm management, but the council was still working on identifying what was causing it, Mr Smith said.
The TDC had yet to decide what to do about the Rabbit Island pollution as the source had not been identified, but the reserve was closed until it was safe to use.
There was little that could be done about cyanobacteria, which flourished when water flows were stable and in rivers with higher nitrogen and low phosphorus concentrations, apart from issuing public warnings and providing information, he said.
It was usually more prevalent in the Motueka and Sherry rivers.
The city council also has its own compliance issues, with warnings in place for people not to swim in the lower Maitai River below the Collingwood St Bridge and at Paremata Flats reserve on the Wakapuka River.
Both sites rated very poorly, with Collingwood exceeding alarm bacteria levels 11 times and Paremata three times last summer.
The council has had difficulty pinpointing the source of the Collingwood contamination but has spent more than $100,000 since 2009 on investigating and repairing sewer, stormwater and wastewater pipes in the area. Further work is planned after it located hot spots in manholes in Collingwood St.
In the Wakapuaka catchment, the council has been working with landowners to fence off the river and its tributaries from livestock, which are a major source of e-coli bacteria in rural waterways. About 2.5 kilometres has been completed. Since 2011, 23 landowners have planted about 5500 plants along riparian margins to help reduce erosion and bacteria runoff. It appears to be slowly making a difference, with the water quality improving from very poor to poor at Hira Reserve and no alarm exceedances over the past two summers.
There was little change at other main beaches and swimming sites monitored by the city council, with all but Sunday Hole and Girlies Hole on the Maitai River retaining good grades, with the occasional exceedance occurring after heavy rain.
The council, which spends $18,000 a year on water monitoring, said dogs and wildfowl were the most likely sources of faecal contamination at urban parkland sites.
Council communications adviser Nan Ward said the council tested regularly for cyanobacteria; it had exceeded the guideline only once, in May at the Maitai River campsite before rain washed it away. There had been no reports of dogs being affected.
If the algae covered more than 20 per cent of the sample site, the public health authority was notified, warning signs put up and vets contacted, she said.
HOW THEY RATE
How the Nelson region's main beaches and swimming areas rate over summer
Tahunanui Beach good
Monaco Wharf good
Cable Bay good
Hira Reserve poor
Paremata Flats very poor
Maitai camp good
Sunday Hole fair
Girlies Hole fair
Collingwood St bridge very poor
Mapua Leisure Park fair
Rabbit Island main beach very good
Source: Ministry for the Environment
* The Tasman District Council also carried out testing for bacteria last summer at Riverview campground on the Buller River, Kaiteriteri inlet, Lee River reserve, Pohara Beach campground, Paynes Ford at Takaka and Tukurua Stream at the campground, but these sites have not been monitored for long enough to be included in the ministry's official ratings which are based on five years of data. Anything rated poor or very poor is regarded as unsuitable for swimming because of the health risks associated with faecal contamination.
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