Quick work protects Battle Hill drinking water after heavy rainfall

Urgent erosion protection works carried out at Horokiri Stream on Battle Hill Farm Forest Park by Greater Wellington following heavy rainfall on 26 August have successfully protected the public water supply from accelerated erosion that endangered the water treatment plant housed in the park’s historic red milking shed. 

Greater Wellington Park Ranger Gary Wheaton and Resource Management Advisor Rachael Boisen Round had previously identified this area as an erosion issue, however, the damage caused by the August deluge required urgent action. 

Mike Harkness, Senior Analyst – Hydrology at Greater Wellington reviewed the Horokiri Stream data, stating, “it was the 7th highest flow on record since the Snodgrass monitoring site was established in 2002”. The park was closed to the public when the stream burst its banks. 

Remedial works took place over three days, beginning with fish rescue, carried out by Greater Wellington experts and assisted by park rangers and a representative from Te Rūnanga o Toa Rangatira. 

Senior Biodiversity Advisor – Fish Passage Project Lead Ashley Webby says, “longfin tuna, kōura, and bully were rescued and transferred out of the impacted zone”.   

More than 140 tonnes of rock were used in the construction of four protective groynes, which along with the excavated material dug in the process of making the diversion channel, formed the erosion protection structure. Hay was spread over the exposed soil and replanted with 200 carex grasses. 

George Bowman, Team Leader of Assets & Performance, was pleased with the collaborative effort. 

“The success of the Horokiri Stream erosion works showcases the power of teamwork within Greater Wellington. By leveraging the strengths of various teams, we were able to respond quickly and effectively, safeguarding a critical public resource under challenging conditions.” 

Battle Hill Farm Forest Park is open to the public and a great location for a day of outdoor leisure activities including walks, camping and farming education/experiences.