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Home My WebLink About0352.092- -'. -~ -- ~'" .... ' ... ' . . ' .~' .- July 23~ 1992 THE HOtoOP.ABLE CITY COUl'iCl L Palo Al'to, Ca. Mosquito nIntestatjon in pDq, Adjacent to thE: _E...GiJo Alto Bav1anos Members of the Council: .E.ru2or.t in Brief This :report des.::ribes the rece!1t mosquito problems in and around the Pe10 Alto Baylands. No Council action is requir~d. BacKground Recent problems wi t!l the r,.'ater level in the Palo A1 to Flood Control Basi" and the pres€rlse of beth fresh and salt INater in the new ITT Marsh have contributed to a significantl}" increas-sd mosquito popu] ati on in the Palo Alto Baylands and adj acent areas t.his ::::umrner. The water level in the Flood Control Basin is :naintained at a minimunl level throughout the year as a :rr,itigation :measure agreed to by the City and the U.S. Army Corps of Engineers related to the operation of the Pa10 Alto landfill. The minimum level maintains relatively healthy estuarine and salt marsh habitats within parts of the Basin. In order to maintain the ~ater level in ~ cost effectiv~ way, an electronic control system .... 'as installed in one of the Basin's tidegates during the early 1970's. Whe~ operating properly, ~his electronic control opens and closes the tidegate automatically, maintaining th.e prC'per w.'ater level. The electronics for the tidegate he,ve had a recent hist.ory of systems failure~ a~d, although the system has been repaired and i~ present.ly operatin:;, properly, it fa i led sor.tetirr.€ beb,ccn June 22 and June 24, 1"992. This fail'...lre left t.he ':idegate in the Hope,," position, allowing tidal water to fill the Flood Control Basin to a higher level than normally allo~ed. This higher level essentially pushed ~ater into part5 of the Basin ;..'hich ordinarily dc-noe have 1,-,rater in then during the s~mrner CMR:j52::92 i I - _"_"' ..... A ,1 £0. L::-;.' Page T',wo months. M~squi-t.o eggs lying jor1':"1ant in the higher parts of the Basin th<="n hdtchca. The larvae found a co~bin3.t.ion of ter.lper-ature, nou~i5hme~t and ~ater in ~hich to survive, and the first hatching of these ~osquitoes occurred as ~ major emergence during the last ,,",'eek of ,J -.!ne. o:'\. discovering the system hcd failed, staff began operating the: tidegate manually, w~ich is the standard fallback procedure. The electronic repair was completed en July 6th. santa Clara County Vector Control ~ist!ict staff increased their monitoring of the palo Altv Baylands for ~Dsquitoes to an average of three times a week beginning early Feb=uary 1992. They began an intensive program of sl...::-veyir".:; and. spra'li]"~g the area's mosquito breeding habitats with a ~acterial agent as soon as the present prcblern became evident. Distr i ct staf f have sprayed for adult mosquitoes ... ·ith insecticide resr.tetr.rin, or !Tscourge," at the Palo Alto Golf course, ho""lever, they believe spraying for adults is less effective than treating the bri'eding habitats. This is because mosquitoes disperse rapidlY upon hatching and the sprays being used creak dowr. rapidly in sunligh.t and have no resid'<.lal effect. District staff met with City staff on July 2nd and again on July 17th to discuss the :rnosquit~ problem. District staff believe the emergence of such a large population of mosquitoes this June was the direct result of the tidegc::!te failure. A contributing factor, both for the present and for the future, is the presence of fresh and salt W'ater in the ne\oll}' created ITT Marsr .. Moscruito lar'v'ae were found in the salt vater sections Df the marsh early in the District's respons~ to the problem. prompt ~ction on the part of District staff, in spraying the salt water areas of the ITT Marsh, probably prevented the emergence of mosquitoes !rorr. becoming an eVen bigger proble..., ef lc:-,ger jurdtion. Elresent Status City staff continue to monitor the y,,'ater-level in the Basin on at least a daily basis. The oper-3..tion of the autol'r,ated tidegate electronics is also being monitor-ed, and staff will begin manual operation of the tidegate if it fails again. One long-term solution to the problem would be the replacement of the tidegate electronics with a ne',.; system. This '"I'ill be pll!'sued as a Capi1:i1l Improvement PrograM. Vector Control District staff az-e continuing to monitor the presence of mosquitoes in the Fl~od Control Basin and the ITT Marsh, and they are spraying or treating the ~ater when necessary. Treatment continues to be a labor-int.ensive process~ because the CHR: 352: 92 .'~ .. . ~ .~. Page Th:-ee er.vironrn~ntally sensitive hai:'itat preclufles the use of mechanize:d treatment mettlods. District and City staff are l!',eeting to develop ways to minimize the e~ergence of riosquitoes in the future. A~ a last resort response to future ernergcnces of m05quitocs~ Cistrict staff re'[1lain available to spn.l}' (c'r adul t nosqui'toes at th,:, Gal f Course. Respectfully submitted, ~a~~ddAuw/ Daniel B. Wil1ia~s Director of "RecrC3i: ion. Oper, Space & scie.,ces /--~ I r-; '-I-~ I ~- Pdul Thiltgen Dir~cto!' cf COriUl.unity Services fu.~w\v~~~ (Jur\ Flemi ng ... ~ssistant City Manager CMR:352:92 • , , ---'"-"-- .--'.