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HomeMy WebLinkAboutCC AG PKT 2010-02-22 #IAGENDA STAFF REPORT DATE: February 22, 2010 TO: Honorable Mayor and City Council THRU: David N. Carmany, City Manager FROM: Jill R. Ingram, Assistant to the City Manager SUBJECT: McGAUGH POOL STATUS UPDATE SUMMARY OF REQUEST: It is recommended that the City Council: 1. Receive and file the report; and 2. Provide direction to staff as appropriate regarding the continued operation of the McGaugh School community pool, with specific direction regarding funding the recommended installation of a "French drain." BACKGROUND: On February 11, 2010 staff met with Los Alamitos School District officials to discuss ongoing issues with the McGaugh pool. As the school district is in the process of demobilizing from their current modernization process on the campus, they have expressed immediate concerns in the ongoing leak from the pool and saturation of nearing soil. As the District nears the end of their project, they have a desire to convert the existing tennis courts into 63 additional parking spots to address the lack of adequate parking. In the process of planning this conversion, the District contracted a geotechnical distress evaluation from a geotechnical /environmental firm regarding the tennis court slab adjacent to the swimming pool to evaluate the condition of the subsurface soils. Attached is a copy of the limited geotechnical distress evaluation by TGR Geotechnical, Inc. In an effort to keep the McGaugh pool operating at its current level, and to address the concern of a future sink hole issue related to ongoing soil saturation within the tennis court slab adjacent to the swimming pool, the geotechnical project engineer is recommending the placement of a "French drain" adjacent to the northwest end of the pool deck. The "French drain" would outlet water runoff to a drainage area near the sports field. Agenda Item Page 2 On Tuesday, February 16th, our City Engineer and staff met onsite with the District's modernization contractor. Our City Engineer is looking at other options to re- direct the outlet water runoff to a drainage area that will not affect the sport fields, and will provide an update at the Council meeting. The District is gathering a more accurate cost estimate, however, the rough estimate for this temporary solution to keep the pool open is approximately $125,000. The District is requesting the City's assistance to fund the requested "French drain" installation. FINANCIAL IMPACT: While the District is gathering a more accurate cost estimate, the rough estimate for this temporary solution to keep the pool open is approximately $125,000. RECOMMENDATION: It is recommended that the City Council: 1. Receive and file the report; and 2. Provide direction to staff as appropriate regarding the continued operation of the McGaugh School community pool, with specific direction regarding funding the recommended installation of a "French drain." SUBMITTED BY: Q�LL'�R - C61 erwn Jill . Ingram, Assistant to the City anager NOTED AND APPROVED: David N. Car any, City Manager Prepared by: Tim Kelsey, Community Services Supervisor Attachments: A. Limited Geotechnical Distress Investigation of Tennis Courts Northwest Side of Swimming Pool A A_J ilk TGR GEOTECHNICAI_, INC. GEOTECHNICAL• January 5, 2010 Los Alamitos Unified School District 10652 Reagan Street Los Alamitos, CA 90720 Fax: (562) 799 -4599 Attention: Mr. Larry Atherton MATERIALS • ENVIRONMENTAL Project No. 09 -2598 Subject: limited Geotechnical Distress Investigation, Tennis Courts Northwest Side of Swimming Pool, McGaugh Elementary School, 1698 Bolsa Avenue, Seal Beach, California. Dear Mr. Atherton, In accordance with your request, TGR Geotechnical, Inc. (TGR) has completed the limited geotechnical distress evaluation of the Tennis Court Slab at the subject site. The work was performed in accordance with our proposal dated December 16, 2009 and your subsequent authorization to proceed. It is our understanding that cracks had developed within the tennis court slab adjacent to the swimming pools. The purpose of the current investigation is to evaluate the condition of the subsurface soils supporting the subject slab and provide mitigation recommendation. SCOPE OF SERVICES The following were performed at the subject site. 1. Site reconnaissance. 2. Concrete coring at five (5) locations within the tennis court. 3. Sampling and Iogging five (5) hand auger borings to a depth of approximately 5 feet below existing slab. 4. Laboratory testing of selected samples to include: in -situ moisture density and optimum moisture content. 5. Preparation of this limited geotechnical distress investigation report, summarizing current sub- surface soil conditions, findings, and presenting mitigation measures. SITE EXPLORATION On December 22, 2009 field exploration was performed by coring the concrete slab at five (5) different locations, and drilling to a depth ranging from approximately 5 feet to 6 feet below bottom of existing slab, and obtaining representative soil samples. The borings were backfilled with cuttings. Patching the borings was not within the scope of services, and was performed by others. The approximate locations of the borings are shown on the Boring Location Map, Plate 1. Relatively undisturbed /grab samples of soils were extracted using modified California Ring Sampler (CRS), 3 -inch outside diameter, and 2.42 -inch inside diameter. All samples were secured in moisture- resistant bags as soon as taken to minimize the loss of field moisture while being transported to the laboratory and waiting to be tested. The borings were backfilled with excess excavated soils. 3037 S. Harbor Boulevard - Santa Ana - CA 92704 - Ph.: 714.641.7189 - Fax: 714.641.7190 09 -2598 SUBGRADE SOIL The sub -grade soil generally consists of dark brown to reddish brown silty sand. The descriptions of the earth materials encountered, along with the densities and moisture contents, are presented in the table below. Soil collapse and erosion was observed in boring B -1 from the subgrade level to approximately 2 feet below the bottom of the tennis court slab. LABORATORY TESTING Moisture and Density Determination Tests: Moisture content and dry density determinations were performed on relatively undisturbed samples obtained from the test borings. The results of these tests are presented below. Where applicable, only moisture content was determined from "undisturbed" or If "& 1 4 4 enmr%lce uaw uvu v Sample Location Soil Description p Moisture ( %} Dry Density (pc* Relative Compaction N B -1 @ SG No Recovery. Voids and Free Standing Water to 2 ft below Grade. - - - B -1 @ 4' Dark brown silty SAND 17.5 - - B -2 @ SG Reddish brown silty SAND 12.7 111.9 88 B -2 @ 4' Reddish brown silty SAND 10.9 120.2 94 B -3 @ SG Dark brown silty SAND 10.0 112.5 88 B -3 @ 4' Reddish brown silty SAND 9.8 120.0 94 BA @ SG Dark brown silty SAND 18.1 109.8 86 B-4 @ 4' Reddish brown silty SAND 12.5 119.4 94 B -5 @ SG Reddish brown silty SAND 9.3 110.1 86 B -5 @ 3' Dark brown silty SAND 9.6 113.0 89 B -5 @ 5' Brown Silty SAND 11.8 120.8 95 Maximum Density Tests: The maximum dry density and optimum moisture content of typical materials were determined in accordance with ASTM Test Method D1557. The-results of these tests are presented in the a_..a 4 4-- .,.,A Gn 4,6 4_61n hclmm acat Maximum Dry Optimum Sample Sample Description Density moisture content Location (pcf) N B-4 (0 to 4') Silty Sand 127.5 9.5 EVALUATION AND RECOMMENDATION Based on our field observation, encountered voids and water, in -situ moisture content, and change in moisture content with lateral and vertical distance it is TGR's professional opinion that the encountered water is a result of leakage from the adjacent swimming pools. Evidence of water and soil erosion /collapse was present in boring B- ladvanced at the southwest comer of the tennis court in the most distress area located adjacent to the swimming pools. The erosion /collapse and free standing water extended to approximately 2 feet below slab bottom. The subsurface molture content is M EL AM , *4 TGR GEOTECHNICAL, INC. 09 -2598 significantly above optimum moisture content in the upper 4 feet where adjacent to the swimming pools and at the southwest corner of the subject tennis court. The subsurface relative compaction varies from 86 percent to 88 percent in the upper 2 feet of the subgrade, with the exception of boring B -1. In order to protect the upper 2 to 3 feet of subgrade from additional seepage water we recommend placing a "French - Drain" at approximately 2 feet below existing grade adjacent to the existing swimming pools. The drain pipe shall be perforated and wrapped in' /, -inch crushed aggregate. The recommended location of the drain is presented on Plate 1, attached. The drain should outlet to an approved drainage area. The slab may be leveled using void filling /compaction grouting. The grout points shall be in a grid like pattern and shall be spaced at 4 feet on center in two- directions. The recommended limit of the grout points is presented on Plate 1, attached. The maximum depth of compaction grouting should be 10 feet below existing grade, and the grout shall be pumped at 2 feet vertical intervals. The grouting operation shall be performed under the full time observation of TGR to ensure that the intent of this report and the recommendations presented in this report are implemented during construction. CLOSURE This report has been prepared for the exclusive use- of Los Alamitos Unified School District and their design consultants relative to the subject project. No portion of this report may be used by other parties or for other purposes. The findings contained in this report are based upon the information obtained from the limited number of test borings and the results of laboratory testing and engineering analysis. As part of the engineering analysis, it has been assumed, and is expected, that the geotechnical conditions, which exist across the site, are similar to those encountered in the exploratory borings drilled. However, no warranty is expressed or implied as to the conditions at locations or depths other than those excavated. Our findings were obtained in accordance with generally accepted current professional principles and local practice in geotechnical engineering. We make no other warranty, either express or implied. This report is subject to review by the controlling authorities for the project. We thank you for this opportunity to be of service to you on this project. If you have any questions regarding this report, please do not hesitate to call this office. Respectfully submitted, TGR GEOTECHNICAL, INC. J. No C070367 It EXP. 9.30.10 aher J. Yazeji, PE, 70387 ; Senior Project Engineer <' % ?`` �'�vl� - r•�';. Attachment: Plate 1— Coring Location Map Distribution: (4) Addressee A IL An EL -3- e. J ®t TGR GEOTECHNICAL, INC.