Snoopy slugs fry sewer switchboards

Adam Twose with some of the slimy culprits short circuiting sewerage system switchboards in Ruakaka. Photo / Michael Cunningham

Ruakaka residents and the Whangarei District Council are slugging it out with a slippery foe that is sabotaging sewerage system switchboards.

Slugs are finding their way into the boxes housing the circuit boards for pumps that shift sewerage from properties to the Ruakaka Sewerage Scheme.

Each of the 479 pumps in the scheme has its own control panel and it seems slugs have developed a fatal attraction for the shady, dry plastic boxes attached to the buildings.

But the slime they leave during their passage across them has caused several of the boards to short out.

Whangarei District Council staff discovered the shocking truth after being called out to investigate several pump failures, and found skid marks across the boards, shrivelled little black things in the bottom of the boxes and live slugs lurking in the vicinity.

Operations engineer Adam Twose said the slimy creatures were being "drawn like a moth to a flame" - except much more slowly - by the minor electrical field given off by the control panels' circuit boards.

"The system has been working really well, with very few issues raised, but we have come across something we never expected.

"According to our pump supplier it is unique to Ruakaka. They have informed us they have not had this issue anywhere else. We had included a number of features in the scheme as a result of lessons learned on pressurised sewer systems around the country but this is a totally new one that has not previously been recorded."

Because the problem could mean potential sewer issues for homeowners, the race is now on for the council's contractor, Hydrotech, to get to the remaining boards before the slugs do.

Workers will be armed with sealant to fill the gaps around the cables where the slugs have been sliding through. At $25 to seal each of the 479 power boxes, the $1200 goo-against-goo solution is far cheaper than replacing the circuit boards at $450 each, "every time a slug gets curious", Mr Twose said.

New Zealand has 30 species of slugs but it is not known at this stage if the Ruakaka ones with a taste for electrocuting themselves are among the few endangered varieties.