Environment Waikato needs to be more involved in subdivision planning to avoid environmental damage from earthworks, this week’s Environment Committee meeting heard.
Forestry and minerals programme manager Grant Blackie said sediment as a pollutant tended to be downplayed by some contractors, consultants and others and was seen as a “natural” response to rainfall events. Cumulative effects of sediment – runoff from several earthworks sites - on water was also difficult to measure.
Sediment discharges from earthworks could be up to 2000 times greater than from land under forest and up to 365 times greater than from pasture.
Effects included degradation of water quality and aquatic ecosystems, infilling of waterways, increased flooding, effects on the use of water for drinking, industrial and recreational use and effects on tangata whenua relationships with water.
Construction activities affected sediment movement by vegetation clearance, exposure of unprotected soil to rain, changing runoff flows and moving and de-consolidating soil. Contractors, consultants and others either did not always understand or were not motivated to take appropriate action to use low impact designs, control soil erosion or sediment discharges from earthworks, he said.
Inter-agency liaison varied enormously between regions, depending on the local issues and agencies involved. Some industry sectors had responded in different ways to the requirement to lift their environmental performance, and there was considerable scope for improved liaison with territorial authorities.
Cr Andra Neeley said guidelines were needed, and the Council needed to look at staged subdivisions. In Taupo a publicly funded riparian planting “took a pummelling” when a subdivision brought a hill down on it.
Chairman Lois Livingston said the Council needed to get more involved in subdivisions and look closely at its plans to see how it could get involved right at the beginning.
Mr Blackie said erosion and sediment control guidelines had been completed and two workshops had been held for territorial authorities and land developers. Consent conditions relating to earthworks and sediment control had also been recently reviewed.
There was increasing demand to lift the standards of earthworks sites. The Council had been light in taking enforcement action, and needed to look at the effect of small cumulative problems, he said.