HomeMy WebLinkAboutLetter from David E. Gallo - TSM16-0002 Testimony regarding TSM16-0002
Dr. David E. Gallo, Professor Emeritus
Environmental and Energy Economics
California State University, Chico
The Leen subdivision map provides a 150 foot setback for structures located within the development
and the agricultural operations to the south. The claim is that the reduction from the county standard
of 300 feet is justified by the presence of a vegetative screen along Comanche Creek. Yet the developers
'have provided no evidence that the discontinuous stand of deciduous trees that constitutes the
"vegetative screen" will offer any significant protection from dust and noise from the large walnut
orchard to the south of the project area.
There has been a considerable amount of research on the effectiveness of vegetative screens,
particularly for reducing dust and odors from poultry operations. However, the tested screening
vegetation bears no resemblance to the vegetation along Comanche Creek. In one study the screen was
a"...three row planting of 4.9 m high bald cypress(9 m from the exhaust fans), 4.3 m high Leyland
cypress (12.2 m from fans) and 2.4 m high red cedar (14.6 m from fans)..."
(http //extension_udel.edu/factshee_ts/using_trees_to-reduce dust-arid odour emissions from-poultry_
farms/). Clearly all of the trees used were evergreens with dense foliage, and the emissions were point
source, emitted through the fans used to ventilate the poultry house. While this screen was somewhat
effective, it was clearly not sufficient to eliminate the nuisance. "Total dust was reduced 53% (0.659 vs.
0.333 mg/m3) and 50% (1.039 vs. 0.527 mg/ m3) in years 2002 and 2003, respectively".
-There are three key points to be taken from this and similar research.
1. An effective vegetative screen requires multiple rows of plantings where each successive row of
trees pulls out a percentage of the fugitive dust.
2. Those plantings need to be composed of dense evergreen trees.
3. To be effective the screens need to be installed close to the pollution source.
The third point is particularly important in the case of the Leen development because it is impossible to
locate any vegetative screen close to the dust source. In addition, no vegetative screen is going to
significantly filter noise. It has be demonstrated that even dense plantings reduce noise levels by only 6
decibels.