The 1996 Grafton flood and the 2016 vote on wind energy 

GRAFTON, Vt. – I thank the Grafton Select Board for inviting me to participate in the October 10, Hydrology Forum. The forum was held to inform the public of the hydrologic, storm water, and flooding issues associated with ridgeline wind development.

The topics discussed included the current state of Lowell Kingdom Community Wind’s storm water management, as it is prototypical of what to expect in Grafton and Windham.

Another topic proposed for discussion was the 1998 report of the Grafton flood of June 12 and 13, 1996 authored by the National Oceanic and Atmospheric Administration (NOAA) and the impact of storms and the mountains on local flooding. Due to the extent of discussions regarding the Lowell KCW project, time ran out to discuss this report.

The storms of June 12 and 13, 1996 impacted much of the southern Green Mountains, but were especially severe on Stiles Brook, the location of the proposed wind project. The storms and resulting flood had origins in a southwesterly unstable air mass, typical of late spring/summer weather patterns. Movement of this air mass over the ridgelines and mountains to the west of Grafton caused thunderstorms to form as a result of solar heating and “terrain forcing”.

In other words, thunderstorms formed over the mountains and ridgelines as a result of the air mass being forced to rise by the terrain. The data collected for the report revealed that eight to nine inches of rain fell over two days. The report concludes that the prediction of storm location is difficult; however, it infers that these storms largely form over the terrain characteristic of the Green Mountains.

Grafton, Windham, or any town located within or around the spine of the Green Mountain range are highly susceptible to such thunderstorms, with runoff draining to the valleys immediately east and west of the mountains. The steep terrain and narrow valleys, as along Stiles Brook and the Saxton River, exacerbate the flood by accelerating and channeling fast flowing waters.

As in the mountainous area of the proposed Windham-Grafton wind project, the largest effective regional storm water management approach with the least need for human intervention is preservation of the forest in these high elevations. In the 2011 ANR report “Resilience, A Report on the Health of Vermont’s Environment”, the forests of Vermont are credited as “[helping to] intercept many downpours, slowing runoff into streams.” So, one can conclude that with human induced climate change the storm water retaining benefits of forests will become even more important going forward.

According to the US Global Change Research Program, between 1958 and 2010 the Northeast experienced more than a 70% increase in high intensity storms. This trend is expected to continue steadily into the future. So then, what is the current administration’s answer to addressing climate change?

It is to promote large-scale industrial wind energy generation plants in the location where rain falls the hardest and the forests provide the greatest benefit in terms of flood resilience in the downstream valleys. The developers will say that ridgeline development is a must as “that is where the wind is”; but its not as simple as planting 400-500 foot tall wind turbines.

In order to build the project, mountainous terrain must be blasted and graded to develop the roads to provide access of trucks and cranes to these high elevations. The natural hydrology is interrupted and redirected, with tens of acres of imperious cover created. To compensate for this change in the natural runoff patterns the Stiles Brook project would contain upwards of 50 plus structural storm water management facilities that would require maintenance in perpetuity.

If these systems fail due to insufficient design or construction, lack of maintenance or poor siting, storm water runoff from the site will increase significantly.

Contrary to others’ position at the forum, it is my professional opinion based on my understanding of stormwater management design, review of the plans and calculations for the project, direct observation of the site, review of aerial imagery, and photographs provided by others, that the Lowell KCW project’s stormwater systems are not functioning to protect downstream resources.

In the best interest of Grafton and Windham, fighting climate change without sacrificing resiliency is better solved with preserving the high elevation forests and building more community scale solar voltaic systems in close proximity and under the control of the residents. That, my friends, would be setting an example for other towns in Vermont…and the world.

This commentary is by Geoffrey M. Goll, who is a founding and managing partner of Princeton Hydro and a 26-year engineer who has been working on renewable energy issues in Vermont for the past six years. He was an expert witness for Energize Vermont during the storm water and wetland permit appeals of the Kingdom County Wind project in front of the Vermont Public Service Board.