City Council Work Meeting

Mayor Hart introduced Sean Amodt, Director of the Southwest Mosquito Abatement and Control District for Washington County and indicated that he and his staff conducted study at Fire Lake Park. He has conclusions and recommendations, should Dry Wash reservoir move forward. Sean Amodt referred to the summary report for the Ivins/Fire Lake Park Reservoir flying insect surveillance project, a copy of which is available as an attachment to this agenda. He reported that four (4) traps were set in various locations around the reservoir from the evening of May 23rd to the morning of May 24th. The average temperature was 74 degrees and the average wind speed was between 5-7 mph. That time of year is typically a moderate to high time of year for flying insects. There are a few environmental factors that can affect the number of flying insects, including the following: Water quality - an imbalance in water quality can cause an increase in flying insect numbers. The amount and type of fish can also affect insect levels; Surrounding vegetation - the amounts and different kinds of vegetation can affect insect numbers; and Reservoir depth - the average depth along shorelines can affect those flying insects that develop mostly in shallow water. Regarding the results of the traps, three (3) traps surrounding the reservoir had an insignificant number of flying insects, mostly containing non-biting gnats. The trap placed in the reservoir discharge wash had an abundance of marsh mosquitoes and a few other insects. In that area the water backs up before Highway 91 which has caused a swampy area to form. Mayor Hart indicated that Public Works will be cleaning that out. Sean Amodt indicated that there were approximately 3500 mosquitos in that area but they do not fly very far because of the type of mosquito that they are and the Mosquito District will continue testing in that area. Their Assessment and Control Recommendations are as follows: In the Reservoir area, the low numbers of flying insects caught near the reservoir should not be much of a concern. Seasonality or environmental changes could cause imbalances and numbers to increase for short periods of time. Those situations could be mitigated by Ultra-Low-Volume (ULV) spray fog in the evenings to avoid non-target insects; traps could be set to attract and contain insects; bacterial treatments to water sources to control larvae and algae; addition of more and different types of fish; vegetation control along the shorelines; and increasing and maintaining the water depth. In the wash area, the high numbers of mosquitoes in that area can be mitigated by treatments through the Mosquito Abatement District for larvae and adult mosquitoes; cleaning and/or clearing vegetation buildup in the lower wash using fire or heavy equipment; channeling the water to flow instead of spreading out; unclogging the blockage at the culvert under the highway; and ongoing monitoring and vegetation control. Regarding future reservoirs, proposed reservoirs can mitigate many issues in design and planning stages by implementing strategies that include water depth where one avoids creating shallow (2 feet or less) areas and the gradual variation of water levels; additional or natural bacterial concentrations to help balance and establish a proper bacterial load in the water source; possible introduction of fish to feed on insect larvae and adults; introduction of aquatic larval predators like dragon flies; vegetation control along shorelines and into drawdown areas; traps placed strategically around the reservoir to attract and contain insects and used for monitoring purposes; pesticide barrier spraying around the reservoir to keep insects contained; and ULV (Ultra-Low-Volume) spray fog on occasions where insects can't be controlled by natural means. Council Member Barton referred to the good bacteria and inquired if there was a visual aspect that could be seen on the water? Sean Amodt indicated that it is regular looking water and the good bacteria reduces that layer of sludge layer and smells. Council Member Gillespie referred to fish as an option for mitigation and commented that the Council was not looking at the Dry Wash Reservoir as a recreational reservoir at this point and inquired if the fish would need to be fished out. Sean Amodt stated that it would depend on the type of fish. Mayor Hart thanked Sean and his staff for the research and information.

Council Member Scott	AYE
Council Member Smith	AYE
Council Member Barton	AYE
Council Member Gillespie	AYE
Council Member Anderson	AYE