Flooding strains Blenheim sewer system

As yesterday’s flood waters began to subside, pump stations started making headway on Blenheim’s overwrought sewer system.

People were given the all clear to flush their loos at about 9pm last night as a perfect storm saw the town’s sewer struggle to keep ahead.

Marlborough District Council operations and maintenance engineer Stephen Rooney says in contrast to last years July 17 flood, more rain fell on southern Blenheim and the Wither Hills, swelling the Taylor River to levels higher than what was seen in the last big flood, slamming the town’s the stormwater system.

“July 17 last year was a flood event that effected a wider part of Marlborough, especially headlands. Our response focused on what was happening on the Wairau River,” Stephen says.

“We didn’t have the heavy rainfall over Blenheim, southern or the Wither Hills.

“Yesterday, we had a lot more stormwater around Blenheim, and the Taylor River came up.”

He says the flood gates were closed on the Taylor, which meant the town’s stormwater relied on pumping to remove the excess.

“When those ponding events occur, we start to get stormwater into the sewer network.

Stephen says when the river gets so high, the groundwater comes up, causing a higher pressure in the sewage pipes.

“All those things cause the sewer system to fail.”

He says they had 12 people actively managing the flooding in Blenheim, as well as six people manning the phones and coordinating teams to the worst hit locations.

The rivers team were also all hands on deck, and contractors from Simcox and Downers leant manpower to keep rivers flowing in the proper place.

Stephen says it’s a shame the flooding event didn’t happen in late October, when the major sewer upgrade in northern Blenheim is completed.

“We are only months away from completing a major sewer upgrade that would have alleviated a large portion of yesterday’s stormwater overflow.

“A significant part of that project is a new pump station with a component of treatment of stormwater flows.

“It will enable us to manage these stormwater events much more effectively.”

Stephen says to avoid playing it ponding water, as there is a possibility it could be contaminated with sewage.

“Once we start getting sewer overflows, it’s probably not that sensible [to come into contact with flood water].

“Treat ponding areas like they are contaminated.

“If you come into contact, practice sensible hygiene. Wash your hands before eating.”

He also has good toilet etiquette advice for during storm events such as yesterday.

“When you flush the toilet, the bowl fills up with all the water in the cistern.

“Flushing a second time soon after, before the water has a chance to drain, is when you get issues.

“The second flush doesn’t have anywhere to go.”

He says if everyone is flushing, it can stress the sewer network.

“We ask people if it’s yellow, let it mellow. If it’s brown, flush it down.

“If you have to, flush it once and wait until it’s empty before you flush again.”

If there was a sewer overflow onto a path or gardens, let council know.

Put lime on grass areas, it will help disinfect anything captured on grass,” says Stephen.

“Concentrate on picking up paper and solids – sunlight will do the rest. And practice good hygiene.”