o~a~ ~o ~~ ~ -~ COMMISSIONERS' COURT AGENDA REQUEST • PLEASE FURNISH ONE ORIGINAL AND NINE COPIES OF THIS REQUEST AND DOCUMENTS TO BE REVIEWED BY THE COURT. MADE BY: Commissioner Williams OFFICE: Precinct Two MEETING DATE: January 25, 2010 TIME PREFERRED: SUBJECT: Consider, discuss information provided by Freese & Nichols regarding general description and typical approach to evaluating and remediating silt accumulation in a typical lake reservoir. EXECUTIVE SESSION REQUESTED: (PLEASE STATE REASON) NAME OF PERSON(S) ADDRESSING COURT: Commissioners Williams & Les Boyd, Freese & Nichols, Inc.. ESTIMATED LENGTH OF PRESENTATION: IF PERSONNEL MATTER - NAME OF EMPLOYEE: Time for submitting this request for Court to assure that the matter is posted in accordance with Title 5, Chapter 551 and 552, Government Code, is as follows: Meeting scheduled for Mondays: THIS REQUEST RECEIVED BY: THIS REQUEST RECEIVED ON: 5:00 P.M. previous Tuesday. @ All Agenda Requests will be screened by the County Judge's Office to determine if adequate information has been prepared for the Court's formal consideration and action at time of Court Meetings. Your cooperation will be appreciated and contribute towards you request being addressed at the earliest opportunity. See Agenda Request Rules Adopted by Commissioners' Court. Freese crr2rl ~ N~chals~ If1C. Engineers Environmentat Scientists Architects P~anners 30814 Jotlyvilte Road, Building 4, 5uite 100 Austin, Texas 78759 December 16, 2009 Mr. William "Bill" Williams Commissioner Precinct No. 2 Kerr County 700 Main Kerrville, Texas 78028 Re: Kerrville Lake Dam, (Flat Rock Dam) Silt Evaluation Dear Mr. Williams: 512-451-7955 512-451-7956 fax www,freese.com We have developed this letter to ~rovide a general description of a typical approach to evahiating and remediating the silt accumtilation in a reservoir. This description is provided to assist you in assessing the silt issues at your Flat Rack Dam in Kerr Coui~ty, Texas. We trust this presentation is in accordance with your interests expressed in our phone conversations of recent weeks. The steps to addressing the silt will be preseuted briefly in bullet fornlat and then described in tnore detail in subsequent sections. The basic silt evaluation/ remediation involves: 1. Quantify the amount of silt present in the reservoir 2. Characterize the silt based upon its physical and che~nical properties 3. Determine an acceptable rernoval method 4. Determine an acceptable disposal method and waste location 5. Obtain all applicable Perrnits 6. Develop construction documents for perforniing the work 7. Select/engage conh•actor to remove/remediateJwaste silt 1. Quai~tify the amount of silt - You indicated in our phone conversatiou that no previous silt surveys have been performed for Flat Rock. This should pose no problem in light of the newest bathymet~-ic survey tecluliques presently available. There are firms which perform bathymetric sutveys based upon radar principles and they can identify and map the top of silt and the lake bottom. The cost of this scrvice is directly proportional to the level of accuracy specified for the project. That is, the determination of silt depths within plus or mimts six inches is more costly than that for silt depth plus or minus one foot. This procedure has been used on other Freese and Nichols projects in Texas. [OFF09041 ] T:~K eir Cowi ty\flatrockdamletter 121 G09rev Mr. William `Bill" Williams Commissioner Precinct No. 2 Kerr County December 16, 2009 Page 2 of 3 2. Characterize the silt - You also indicated in our phone conversation that there were no known test results for the silt. Silt samples will need to be gathered as part of the initial evaluation. These samples will be tested for the presence of contaminants such as pesticides, lierbicides, heavy inetals, PCBs, and other contaminants which will affect the disposal options associated with the silt. Ttiese tests vaiy in complexity and cost and a sampling program would be developed to adequately satisfy the regulatory agencies involved. 3, Deternline an acceptable removal method - There are generally two removal methods for silt from a reservoir. The ~rst is mechanical excavation using standard hoes, draglines and associated hauling equiprnent to move the silts offsite. The second rnethod is typically hydraulic dredging which involves pumping the silt from the reservoir and either spreading it out to dry or placing it into hauling equipment for remaval from the site. The cost for either of these methods is highly dependent ori the quantity of silt to be handled. 4. Detennine an acceptable disposal method and ~vaste location - The disposal method for the silt can vary from simply removing it and placing it on available farmlands to sending it to a regulated landfill. It is also possible that the silt will need remediation before it can be removed from the site. All of the options for dispasal are dependent on the test results on what the silt actually contains. Without test data one can only speculate on how the disposal will occur. 5. Obtain all applicable permits - This task can prave to be one of the most daunting associated with silt removal. The Corps of Engineers will likely require a 404 pernlit for the material to be removed from the reservoir. In additioYl the Texas Commission on Environmelital Quality {TCEQ) may be involved with pennitting the silt disposal dependent upon its contaminant contents and disposal method. These permits are not necessa~•ily hard to acquire, but they can take an extensive aniount of time, on the order of six months to a year or more. Perrnit applications are typically filed once the dredging quantity is evaluated, silt chai•acterization testing is performed, and a disposal lacation is determined. 6. Develop construction documents for perfonning the work - This is actually one of the most straightforward tasks associated with the silt removal. A project approach will be developed for the removal method, remediation as necessary, and disposal. The most significant task will be locating and obtaining acceptable waste locations or re-use procedures. This phase would result in project plans and specifications for the silt removal project. 7. Select/engage contractor to remove/remediate/waste silt - This phase of the project would be simply obtaining competitive bids from experienced contractors to perform the project work in accordance with the plans and specifications developed in Step 6 and in accordance with the permit requirements in Step 5. [OFF09041 J T:UCerr County\flatroc kdamletterl2 i 609rev ,: Mr. William "Bill" Williams Commissioner Precinct No. 2 Kerr Cotinty December 16, 2009 Page 3 of 3 The approach to the silt question at Flat Rock Dam should, in our opinion, evolve generally along the above listed sequence. When quantity surveys and silt characterizatior~/testing results are obtained, project costs can be addressed for use in Kerr County's planning and budgeting process. We will be glad to assist yau in any manner you choose, should you decide to proceed with the silt evaluation prograrn. We have worked with bathymetric surveying firms on similar projects and with qualified testing firms. We are available to put together the first components of this evaluation. Please call me at S 12-617-3117 if you have any questions or comments. Sincerely, FREESE AND NICHOLS, INC. ~._~~ . j~~~,,~-;!,f,~~c'~,, ~W_. . ~ ~ M. Leslie Boyd, P.E. Associate [OPP090a1] 'f:\Ken• Countylflatrockdamletter121609re~-