To: Honorable Mayor and Members of Town Council
From: Mark Marlowe, PE, Director of Castle Rock Water
Title
Update: Mosquito Abatement Program
Body
________________________________________________________________________________
Executive Summary
In order to prevent cases of West Nile Virus, the Town began treating all public drainage areas in 2003, through a joint effort with Douglas County and the Tri-County Health Department. Non-invasive, environmentally safe measures were used to eradicate mosquito larvae and prevent them from becoming adults. At that time it was determined that no spraying, for adult mosquitos, would be done without prior notice to residents. These tactics are still in effect today. Castle Rock Water oversees the Mosquito Abatement Program for the Town as stormwater ponds are a primary location used for mosquito control.
Notification and Outreach Efforts
Public outreach regarding mosquito control on private property has been conducted through articles in Town Talk and on the CRgov.com website FAQ page. On CRgov.com a link has been set up that takes the resident directly to the Town’s mosquito abatement contractor Vector Disease Control International (VDCI). The VDCI website provides education regarding mosquitos, home mosquito prevention, and their surveillance and treatment programs. From the Contact Page residents can send an email or call VDCI with any questions or complaints they may have. Data from 2011 through 2018 shows that most customer mosquito calls are received during the months of July and August, but can vary seasonally, depending on when monsoonal moisture arrives, (see Attachment A).
History of Past Town Council, Boards & Commissions, or Other Discussions
On March 27, 2019, this item was presented to the Castle Rock Water Commission and the Commission recommended that Castle Rock Water continue with the Mosquito Abatement Program.
Discussion
Initially, the Town operated the mosquito control program internally, through its Public Works and Utilities Departments. Since 2010 the program has been operated through contractors that were vetted by a competitive bid process. Costs for the mosquito abatement program have remained relatively consistent, starting out at $23,850 in 2010 and going to $24,711 in 2018.
A Request for Proposal (RFP) was posted on BidNet in 2018 and respondents submitted quotes for mosquito control services for the Town. Currently, the Town is scheduled to renew their services agreement with VDCI, which is in the second year of a three year agreement. The Castle Rock mosquito treatment map identifies possible mosquito breeding areas, (see Attachment B).
From May through September, VDCI is contracted to survey stormwater areas based on each site’s ability to support the growth of mosquitos. They also set up adult mosquito traps which enable the contractor to determine specific species and quantities of mosquitos found at each site. Specific mosquito species, such as Culex pipiens, are known to spread West Nile virus. Determining the dominant type of mosquito allows the vendor to estimate the possibility of disease transmission.
Depending upon the amount of moisture, organic matter and ponding at each site they then distribute Vectobac or Vectolex, naturally occurring soil bacterium that inhibit mosquito larvae development. Spraying for adult mosquitos is considered a last resort measure and has yet to be performed in the Town. VDCI sends monthly reports to the Tri-County Health Department and also to the mosquito program manager at Castle Rock Water. VDCI completes an annual report at the end of each year. A copy of the 2018 annual report has been provided, (see Attachment C).
Comparisons of VDCI’s mosquito report data, taken from surrounding municipalities treated, shows that the Town has similar mosquito trap counts as Centennial and Arapahoe County, but much lower quantities than the Parker and Columbine Valley areas, (see Attachment D). The key to controlling adult mosquito populations is in preventative larval treatment. The number and location of sites can vary year to year, depending upon summer precipitation.
Budget
In 2019, staff has reevaluated the scope of work for VDCI, as there has been significant growth in Town, since the implementation of the program. Costs for 2019 will be approximately $26,595, which includes a 5% contingency and will come from the Stormwater Field Services Other Professional Services account 212-4440-444.30-70.
Staff Recommendation
Staff recommends continuing the Mosquito Abatement program as presented.
Attachments
Attachment A: Recap 2011-2018
Attachment B: Treatment Maps
Attachment C: VDCI 2018 Annual Report
Attachment D: VDCI Area Trap Counts 2018