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HomeMy WebLinkAbout1992-01-27 LYMAN CREEK WATER SYSEM IMPROVEMENTS - CId / 9 I / Gaston Engineering & Surveying January 27, 1992 W.O. # 86-511-3 Phill Forbes City of Bozeman P. O. Box 640 Bozeman, MT 59715 RE: Lyman Creek Water System Improvements Dear Phill, Enclosed please find a draft of the information you requested regarding the DNRC loan for the Lyman Creek Water System Improvements. (I have included a copy of the guidelines for preparing this report, to refresh your memory.) Items 2, 3, & 4 are probably best answered by your staff, however, if you need assistance, please advise. This enclosure should clean up items needed from us. If you have any questions, please feel free to give me a call. Y . Ga o , P.E. Enclosure GG/zdb Consulting Frtgineers & Lend Surveyors I'() II, I I I I N.;Lh Avv,Iito-it wit.NIT 59i 15 1106);;hi;115.148 tillw'I'It lµ'l rltU'I',l2n ll' LI';Inlh',I101h'.M I ('II1(;)7'15JII:S January 24, 1992 W.O. # 86-511--3 LY11L4N CREEK WATER. SYSTEM IMFR0VE,MEN TS Y. HISTORY Or, PROJECT A. There are two major sources of supply for domestic water for the City of Bozeman. The main source comes from the Sourdough & Hylite. drainage. This water is treated using filtration and chlorination. The second source is located at Lyman Creel. This source (Lyman Creek) consists of water originating at a spring in the Lyman Creek drainage. The water originally flowed in a stream to a diversion structure located approximately 3/4 of a mile from the spring source where water was collected in a pipe line and diverted to a open reservoir. This reservoir supplied water to a portion of the City of Bozeman Water distribution system located on the north side of the interstate. The newly enacted Safe Drinking Water Act requires that all water sources that consist of surface supplies be filtered and disinfected. The problem that existed with the Lyman Creek water supply was that as long as the reservoir and supply were open to the atmosphere, they would be considered a surface supply. In checking with the MT Department of health & Environmental Sciences, we determined that if the reservoir was covered and if a pipe line was installed to the spring and the spring source covered, that the water supply would not require filtration. The cost of constructing a filtration plant would far exceed the cost of constructing a pipe line. B. The project selected to enclose the (Lyman Creep) water supply was to install a pipe Iine from the spring source to the existing pipe line which is currently connected to the existing diversion and install a chlorination system with flow metering and reservoir cover. Several alternate solutions for covering the reservoir including a wood roof, structural concrete roof, and a flexible floating cover were researched. The flexible floating cover was selected because of the low initial first costs. Several routes for installing the pipe line were evaluated including using ball joint 2 Lyman Creek Water System Improvments January 24, 1992 pips Iaid on the surface of the existing ground. The alternate selected was to install ductile iron pipe underground on the south and east side of the stream. Spring development was accomplished by driving sheet piling into and around the Spring source similar to a cut-off wall. Two cut--off walls were installed at two specific sources. The spring areas were then covered with a clay cap and seeded with native grasses. C. DESIGN ENGWEER: Gaston Engineering & Surveying, p.C, P. O. Box 861. Bozeman, M`1' 59715 (406) 586 -0588 Gerald M. Gaston, P.E. PROJECT INSPECTOR: Gaston Engineering & Surveying, P.C. P. O. Box 861 Bozeman, MT .59715 (406) 586-0588 Julian Dodge, TEC11 Brent Miller, CET CONTRACTORS: Phase I/Il (Reservoir Cover &, Phase I Pipelilae) Nelcon, Inc. P. O. Box 2667 Missoula, M;l" 59806 (406) 721-1733 Phase X (Spring Source & Phase II Pipelifce} Bozeman Sand & Gravel P. O. Box 1327 .Bozeman, MT 59715 (406) 586-2211 D. Phase Z & 11 - This portion of the project consisted of a floating, reservoir cover and first phase of pipe tine. Subcontractor on the floating cover was Gundle Lining of Texas. The reservoir was drained and the floating cover installed against the dry sides of the reservoir. Take up reel and pulleys were installed around the perimeter of the reservoir to 3 Lyman Creek 'Water System Improvments January 24, 1992 pull the surplus cover material to the sides when the reservoir was filled. Phase 11 consisted of the chlorination building utilizing ton cylinders and flaw metering and chlorine residual monitoring. Pipeline installation consisted of connecting to the existing pipeline and by passing the existing diversion. The initial phase of pipeline construction consisted of installing pipe to the mouth of the narrow canyon and installing a small diversion darn. Construction was done by Nelcon, Inc. of Missoula. Engineering design, construction layout and project inspection was provided by Gaston Engineering & Surveying. Phase III consisted of completing the pipeline into the narrow carryon and to the spring source, Improvements were also completed at the spring source to cover the area with a clay cap and to install cut—off walls to help concentrate the underground water. Construction was done by Bozeman Sand & Gravel, Engineering design, construction layout and project inspection was provided by Gaston Engineering & Surveying. E. The water supply and source are entirely enclosed, disinfection and chlorine residual is currently being performed with weekly results being forwarded to the, MT Department of Health & Environmental Sciences. The project meets State and Federal requirements for both biological and chemical quality. Turbidities have been reduced due to the elimination of surface contamination. The project is considered a success in meeting State and Federal criteria as well as assisting in meeting the water demands for the City of Bozeman. F. Spring collection system utilized interlocked sheet piling. 'These pilings were driven to refusal and cut off at uniform heights. The other option was to excavate and place structural reinforced concrete cut off walls at specific location. Spring development is a sensitive area where construction can change the spring source or possibly destroy the source. By utilizing sheet piling disturbance of the surrounding area was kept to a minimum and the danger of interfering with the spring source minimized.ized. 4 Lyman Creek Water System Improvments January 24, 1992 G. Problems were encountered in the construction of the pipe line in Phase III. Rock lay6rs were encountered at or near the design depth of the pipe line. Extensive efforts to remove this rock layer were exerted during pipeline construction, Slope stability was also a problem trying to hold slopes ire--place while excavating for Pipe line installation. Project costs were within budget and change orders kept to a minimum.