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i Minnesota Pollution .Control Agency r 520 Lafayette Road, Saint PauInMinnesota 55155 44 Teleph.one.(612_) 296-6300 t: j ,*C,; {-^£1 ^ * MtNMSOIA 1««0 • % • '• •«. «!• November 27, 1989 Sergeant Pill Chandler Hennepin County Water Patrol Post Office Box 187 Spring Park, Minnesota 55384 Dear Sergeant Chandler: I appreciate the opportunity to have participated In the personal watercraft noise testing on September 29, 1989, at Lake Minnetonka. It's hard to believe that only 8 weeks ago I was tempted to roll my pants up and wade In the water to cool off! Attached Is a copy of your test results to which I added ray results. Since my microphone was set up at the corner of the dock platform, the open-throttle pass-bys may not have been at exactly 50 feet. Also, I was not looking for a maximum level during the 50 foot Idle pass-by, but rather a minimum range. The following numbers are the result of logarithmically averaging the data on both types of watercraft: (log) average maxlmums: 050', 0100', 0300', 0400', 0500' modIfled: 87 85 stock: 80 77 Modified - vehicle 1,2,3. Stock - 5 didn't fit In either category so 62 71 68 64 61 vehicle 4,6,7,3,9,10. Vehicle I left It out. Two vehicles of each type were monitored at “play" for a few minutes. t was curious to see how close to shore they could operate and be within the State's ambl.!nt noise standards for residents on shore. Two stock vehicles, assuming they stayed in the same area for an hour, would appear to be within limits at distances beyond 200 feet. Two modified vehicles, under the same conditions, would need to be beyond 500 feet. Regional Ollices: Duluth • Brainerd • Deiiort Lakes • Marshall • Rochester Equal Opportunity Empteyer P'lnlad on Recycled Paper ; I I 1