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Activity no: 10-06588 41/ Describe the reason for the proposed alternative: We would like to use a double layer of clear 6 mil polyethylene covering on the roof and a single layer on the sidewall. It appears to be the industry standard for covering greenhouses. A review of membrane materials by interne search and by Oregon Valley Greenhouse have found no replacement materials that meet FAR 701 and still let enough light through to grow quality plants under(60% shade would create leggy plants during the spring growing season that would be unsaleable). The proposed alternative is beneficial in the following ways: 1. Each layer lets approximately 90%light transmission(about 80%light transmission on the double wall roof). 2. Polyethylene has a good thermal property(U .7 value)which is better than glass or single wall polycarbonate. This would help with heat retention in the spring growing season. 3. There are no seams or small panels to allow heat leakage. 4. In a verbal conversation with Woodburn Fire Marshall Paul Iverson,he indicated that in a greenhouse environment that polyethylene was an excellent choice because it is self—extinguishing and one could readily go through the sidewall if 1610 necessary. 5. By using polyethylene on the sidewall,a roll up could be used which could be used for summer cooling in lieu of running exhaust fans. Describe the why,how,etc., the proposed alternative is equivalent and meets the intent of the code in terms of"strength,effectiveness,fire resistance,durability, health,and safety". Chapter 31 in the building code covers membrane type structures. Marion County Building Department has said that for a retail garden center that the membrane covering the structure must meet FAR 701. We believe the intent of the code is to ensure that no building is constructed of materials that may cause a fire hazard. The submitted flammability report shows that the polyethylene film is self-extinguishing and thus will not burn on its own. When we take into account that the green house frame is steel and it would be filled with live plant material that is non-combustible, there would be nothing to fuel the fire that happens to ignite. While the proposed structure is approximately 6000 sft,one has to take into account that there are 6 exterior exits. Each 40X55 greenhouse will have exit doors on each end, which would mean a travel distance of less than 50 ft to exit the building in case of