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HomeMy WebLinkAboutPurissima Hills Water District (9)26375 Fremont Road Tel (650) 948-1217 Los Altos Hills, CA 94022 Fax (650) 948-0961 August 3, 2000 Town of Los Altos Hills 26379 Fremont Road Los Altos Hills, California 94022 Drilling of Emergency Production Well on Town Hall Site RECEIVED uo 0 3 20na TOWN OF LOS ALroS HILLS Enclosed for your review and comment is a copy of the Purissima Hills Water District's Initial Environmental Study for the construction of an emergency water supply well on your property, as well as the Notice of Preparation of Proposed Negative Declaration and Negative Declaration. The Notice, of Preparation is scheduled to be published on Tuesday, August 8, in the San Jose Mercury News. The comment period is thirty days from date of publication. Enclosures Sincerely, Lucy E. Xavier District Secretary Service To The Hills Since 1955 Y PURISSIMA HILLS WATER DISTRICT NOTICE OF PREPARATION OF PROPOSED NEGATIVE DECLARATION DRILLING OF EMERGENCY PRODUCTION WELL Notice is hereby given that the Purissima Hills Water District has prepared a Proposed Negative Declaration, in accordance with the California Environmental Quality Act ("CEQA"), on a project to drill an emergency production well approximately 400 feet deep and 10 to 12 inches in diameter in the Town of Los Altos Hills. The project site is located near the northeast corner of the Los Altos Hills Town Hall property in the Town of Los Altos Hills in Santa Clara County, California. Copies of the Proposed Negative Declaration and the accompanying Initial Environmental Study are available without charge at the District's administrative office, 26375 Fremont Road, Los Altos Hills, California 94022, during office hours. The project will not have a significant effect on the environment. Written comments on the Proposed Negative Declaration may be submitted to the District at the above address in the care of Patrick Walter, General Manager of the District, for thirty days from this date of publication. The proposed project will be discussed at the public meeting of the Board of Directors at 7:30 pm on Wednesday, September 13, 2000, at the District's administrative office. Dated: August 3, 2000 Patrick D. Walter District General Manager 802354.1 PURISSIMA HILLS WATER DISTRICT NEGATIVE DECLARATION DRILLING OF EMERGENCY PRODUCTION WELL 1. Description of the Project: The project consists of the drilling of a production well approximately 400 feet deep and 10 to 12 inches in diameter in the Town of Los Altos Hills. A production well will only be drilled if a test well, to be drilled at the same location, indicates the likelihood of producing at least 200 gallons per minute. The primary purpose of the project is to provide an emergency water supply for the Purissima Hills Water District in the event that service from the District's sole present source, San Francisco's Hetch Hetchy system, is interrupted. The most probable event that could cause such an interruption is a major earthquake. 2. Location of the Project: The project site is located near the northeast corner of the Los Altos Hills Town Hall property in the Town of Los Altos Hills in Santa Clara County, California. 3. Proposed Finding: The project will not have a significant effect on the environment. 4. Initial Environmental Study: The reasons supporting the proposed finding are set forth in the Initial Environmental Study, a copy of which is attached. The Initial Environmental Study was prepared by Berryman & Henigar, Inc., District Engineers for the Purissima Hills Water District. A copy of the study may be obtained at the District's administrative office, 26375_ Fremont Road, Los Altos Hills, California 94022. Mitigation Measures: Since no potentially significant environmental effects, no mitigation measures are required or appropriate. Dated: September 13, 2000 Patrick Walter District General Manager 802342.1 INITIAL ENVIRONMENTAL STUDY CONSTRUCTION OF AN EMERGENCY WATER SUPPLY WELL LOS ALTOS HILLS TOWN HALL SITE TOWN OF LOS ALTOS HILLS AND SANTA CLARA COUNTY, CALIFORNIA PURISSIMA HILLS WATER DISTRICT 26375 FREMONT ROAD LOS ALTOS HILLS, CALIFORNIA 94022 INITIAL STUDY I. BACKGROUND A. Lead agency: Purissima Hills Water District B. Address: 26375 Fremont Road Los Altos Hills, California 94022 C. Name, address and phone number of person to be contacted concerning this project: Patrick Walter, General Manager Purissima Hills Water District 26375 Fremont Road Los Altos Hills, California 94022 (650) 948-1217 II. PURPOSE AND DESCRIPTION OF PROJECT The Emergency Water Supply Well Project proposes to drill a production well approximately 400 feet deep and 10 to 12 inches in diameter, to be located near the northeast corner of the Town of Los Altos Hills Town Hall property (see Figures 1 and 2). A production well will be drilled only if a test well, to be drilled at the same location, indicates the likelihood of producing at least 200 gallons per minute (gpm), which is the minimum yield deemed useful to the District even under emergency conditions. The purpose of this project is to provide an emergency water supply for the Purissima Hills Water District in the event that service from the District's sole present source of water, San Francisco's Hetch Hetchy system, is interrupted. The most probable event that could cause such an interruption is a major earthquake. The District will not use the well for normal service since groundwater quality in this area, while potable, is highly mineralized. Thus there will be little or no impact on groundwater levels in the area. The first phase of the project will be test hole drilling. The test hole will be 7- to 8 -inches in diameter and approximately 400 feet deep. During drilling operations, a hydrogeologist will be on site to observe the work and document subsurface conditions. Samples of the cuttings taken at selected intervals will be geologically logged. Sieve analyses will be run on these samples for well screen slot -size determination, as required. Following drilling, an electrical log, consisting of resistivity and spontaneous potential will be run. There is no test pumping associated with this task, only drilling and logging. The work requires a drill rig on site. The District will periodically remove the material removed from the hole from the site using their loader and truck. Drilling mud will be recirculated and kept from flowing offsite. After all exploratory work has been completed, the test hole will be "destroyed" (i.e., filled) per 1 Santa Clara Valley Water District (SCVWD)/State Department of Water Resources (DWR) requirements. A production well, if warranted by the test hole results, will be designed. It will be drilled adjacent to the test hole site, a few feet away. The drilling procedure for the production well will be similar to that employed for the test hole except the hole will be larger, requiring the removal of more material, which will also be trucked from the site. Additionally, casing and screens will be installed, as well as a gravel pack and concrete surface seal all in accordance with SCVWD/DWR requirements. A hydrogeologist will be on site to observe the drilling process, the installation of casing and screens, the placement of the gravel pack and the installation of the surface sanitary seal. The completed well must be developed and then test pumped to establish the safe yield of the well. The pumping test will be performed in accordance with applicable SCVWD/DWR requirements. Drawdown and recovery measurements will be taken in order to determine the safe yield for the well. A report will be prepared by the hydrogeologist summarizing information collected during the project, including the basis for estimating safe yield. A conceptual design of the well station has been developed, as shown on Figures 3 and 4. The well station will include the following features: 1. Well Puma - The size and characteristics of the pump selected will depend on the safe yield and drawdown data for the well. The pump will be a submersible -type unit, likely 6- or 8 -inches on diameter. 2. Surface Construction Features - All openings at the top of the well will be capped or plugged to prevent the entrance of surface water and foreign matter. As shown on Figure 4, the well will be equipped with a screened and vented casing vent, an air release valve, a pressure gage, a sample cock and a flowmeter. All piping will be ductile iron pipe. 3. Electrical Panel - Pump switchgear and controls will be housed in a small panel adjacent to the well. 4. Chemical Feed and Storage Facility - Chlorine gas (i.e., in pressurized cylinders) will not be used at the well facility. Chlorine in this form is hazardous. Sodium hypochlorite (i.e., a more concentrated version of household bleach) will be used. Being a liquid, it does not present a gas release hazard. The chemical and its feed pump will be housed in a small building adjacent to the well to provide containment in the event of a spill and to mitigate against vandalism. No chemical will be kept on site unless an emergency condition exists, requiring the use of the well, since the chemical deteriorates with extended storage. When on site, the sodium hypochlorite solution will be stored in plastic 2 drums or tanks which will be double -contained. Double -containment is a requirement of fire authorities and OSHA. The volume of sodium hypochlorite needed on site will depend upon the capacity of the well, which is now an unknown because neither a test hole or the well itself has yet been drilled. The District's target capacity is in the 200 to 500 gallon per minute (gpm) range. Assuming an average chlorine dose (i.e. 3 parts per million), the daily hypochlorite solution requirement would range from 7 gallons per day (gpd) at a 200 gpm well production rate to 18 gpd at 500 gpm. This is equivalent to a chemical requirement of 50 to 125 gallons per week. III. ENVIRONMENTAL SETTING A. INTRODUCTION The project area is located entirely within the boundaries of the Town of Los Altos Hills and the County of Santa Clara. The emergency water supply well will be located immediately west of the Los Altos Hills Town Hall parking lot approximately 150 feet east of Fremont Road, B. GEOLOGICAL SETTING The Purissima Hills Water District engaged Geoconsultants, Inc. to perform a geological and geophysical survey for locating possible sites within the District for constructing one or more emergency supply wells. The full text of their report, dated August 26, 1998, is included as Appendix A. The following is a description of hydrogeological conditions in the area which has been taken from this report: "The area surveyed is on the west side of the Santa Clara Valley, in Los Altos Hills, California. The majority of the District is underlain with rocks belonging to the upper Pliocene to lower Pleistocene Santa Clara Formation. This unit consists of weakly to moderately consolidated lenticular beds of pebble and cobble gravel with lesser amounts of sand, silt, and clay (Pampeyan, 1993). This unit was deposited in a fluvial and alluvial setting as streams drained the highlands to the west. Cummings (1968) divided the Santa Clara Formation into several distinct lithofacies based on clast composition. According to Vanderhurst and others (1982), the Arastradero facies is overlain by the Searsville facies in the Los Altos Hills area. Gravels of the Arastrasdero facies consist mainly of red chert, graywacke and arkosic sandstone, laminated siliceous shale, and siliceous volcanic rocks enclosed in a fine sand matrix (Cummings, 1968). The Searsville facies gravels are composed of greenstone, graywacke, and arkosic sand stone clasts, with chert clasts being subordinate (Cummings, 1968). The Santa Clara Formation unconformably overlies rocks of Pliocene and older age, and may be as thick as 500 feet in the study area (Pampeyan, 1993). "The primary ground -water reservoir materials are the sands and gravels found in the Santa Clara Formation. The underlying bedrock formations, such as the Ladera Sandstone 91 and the Monterey Shale, are generally considered to be non -water bearing unless highly fractured. Some geologic structures including minor faults and folds occur within the survey area, and may create compartments and barriers to ground -water flow in some instances. "In general, ground -water is produced from those materials exhibiting a .more granular nature, such as gravels and sands within the Santa Clara Formation. Our survey was directed toward identifying such favorable environments with particular reference to delineating the thickest sections of saturated materials in the subsurface portions of the Santa Clara Formation. Locations exhibiting the thickest sections of saturated material will have the best potential to supply the maximum quantity of ground -water to production wells." C. BIOLOGICAL SETTING The area supports a growth of native grasses and trees which are typical of the Oak -Woodland Biotic community which is common throughout the Town of Los Altos Hills. The following lists include those birds, mammals, and reptiles which have been observed in the Los Altos Hills area and may be considered as possible and occasional users of the property. Representative Vertebrate Fauna include: MAMMALS BIRDS REPTILES Bobcat Bushtit Mockingbird Alligator Lizard Chipmunk Dove Owl Fence Lizard Cotton Tail Chickadee Pigeon Horned Lizard Coyote Gndtcatcher Quail Newt Mule Deer Finch Robin Garter Snake Grey Fox Flicker Sparrow Gopher Snake Pocket Gopher Flycatcher Swallow King Snake Deer Mouse Hawk Thrasher Rattlesnake California Mouse Hummingbird Towhee Skink Bush Rabbit Jay Warbler Red -legged Frog Shrew Crow Wren Yellow -legged Frog Wood Rat Kingtit Wrentit Coast Range Newt Vireo Bat (any species) Rabbits and deer have been observed occasionally in the past within the area, however none of these has been observed as residents. None of the plant communities, wildlife or plant species observed are considered significant or of such limited occurrence as to justify protection. No threatened or endangered species as established by the U.S. Fish and Wildlife Service have been observed on the site or are believed to occur on the site because of a lack of suitable habitat. El IV. IDENTIFICATION OF ENVIRONMENTAL EFFECTS A. ENVIRONMENTAL CHECKLIST A review of the environmental impacts of this proposed project has been undertaken in accordance with the California Environmental Quality Act and the implementing regulations and guidelines issued by the California Resources Agency. The review is divided into two parts. The checklist which follows indicates, for each of a number of potential areas of impact, whether the project will, will not, or might produce an effect. Thereafter, in Part IV B, there is a discussion of certain areas of impact in which the review indicates the possibility of an effect. Those items marked with an "asterisk" are the subject of further explanation in Part IV.B although these items are not deemed to identify areas of significant impact. 5 Yes Maybe No 1. EARTH Will the project: a. Cause unstable earth conditions or changes in X geologic substructures? b. Disrupt, displace, compact or cover the soil? X* C. Change the topography? X d. Affect a unique physical feature? X e. Increase soil erosion? X f. Change deposition or erosion of a beach, a X stream channel, or the bed of a water body? g. Expose people or property to hazards such as X earthquakes, landslides, mudslides, or ground failures? 2. AIR Will the project: a. Emit air pollutants, or cause air quality to X* deteriorate or contribute to an air quality violation? b. Create objectionable odors? X C. Change the local or regional climate? X 3. WATER Will the project: a. Change the flow of water in marine or fresh X waters? b. Change the infiltration rate, the runoff rate, X or the drainage pattern? Cl Yes Maybe No 3. WATER Will the project: (cont.) C. Change the course of flow of flood waters? d. Change the amount of water in any body of water? e. Change the quality of surface waters? f. Change the direction or rate of flow of ground - waters? g. Change the quantity and/or quality of ground - waters? h. Reduce the amount of water otherwise available for public water supply? i. Expose people or property to water -related hazards? j. Change the temperature, flow or chemical content of surface thermal springs? 4. PLANT LIFE Will the project: a. Change the diversity of species, or the number of plants? b. Reduce the numbers of unique, rare or endangered plants? C. Introduce new species of plants into an area, or create a barrier to normal replenishment of species? X X X* X* X* X MM X X* X X U. Reduce acreage of a crop? X 7 • 'b Yes Maybe No 5. ANIMAL LIFE Will the project: a. Change the diversity of species, or the numbers X of animals? b. Reduce the number of unique, rare or endangered X animals? C. Damage fish or wildlife habitat? X 6. NOISE Will the project: a. Increase noise levels? X* b. Expose people to severe noise? X 7. LIGHT AND GLARE Will the project: a. Produce new light and glare? X 8. LAND USE Will the project: a. Change the present or planned land use of an X area? b. Use Prime Agricultural land, or lands from a X Timber Production Zone? 9. NATURAL RESOURCES Will the project: a. Use more natural resources? X b. Deplete nonrenewable natural resources? X 10. RISK OF UPSET Will the project: a. Cause an explosion or release hazardous sub- stances? b. Interfere with emergency response or emergency evacuation plans? 11. POPULATION Will the project: a. Alter the location, distribution, density or growth rate of the human population in the area? 12. HOUSING Will the project: a. Affect existing housing, or create a demand for additional housing? 13. TRAFFIC/CIRCULATION Will the project: a. Generate more traffic? b. Affect parking facilities, or need new parking? C. Affect transportation systems? d. Alter circulation patterns? e. Alter water, rail or air traffic? f. Increase hazards to vehicles, bicycles or pedestrians? 14. PUBLIC SERVICES Will the project affect: a. Fire protection? b. Police protection? 9 Yes Maybe No X X* X X X X X X X X X 14. PUBLIC SERVICES Will the project affect: (cont.) C. Schools? d. Parks and other recreational facilities? e. Maintenance of public facilities, including roads? f. Other governmental services? 15. ENERGY Will the project: a. Use substantial amounts of fuel or energy? b. Increase the demand for energy? 16. UTILITIES Will the project affect these utilities: a. Power or natural gas? b. Communications? C. Water? d. Sewer or septic tanks? e. Storm drainage? f. Solid waste and disposal? 17. HUMAN HEALTH Will the project: a. Create a hazard to health (excluding mental health)? b. Expose people to potential health hazards? 10 Yes Maybe No X X X X X X X X X* X X X X X 18. AESTHETICS Will the project: a. Obstruct a scenic view that is open to the public, or create an ugly view? 19. RECREATION Will the project: a. Affect recreational opportunities? 20. CULTURAL RESOURCES Will the project: a. Affect a prehistoric or historic archaeological site? b. Affect a prehistoric or historic building, structure or object? C. Cause a physical change which would affect unique ethnic cultural values? d. Restrict existing religious or sacred uses within the potential impact area? 21. MANDATORY FINDINGS OF SIGNIFICANCE a. Does the project have the potential to degrade the quality of the environment, substantially reduce the habitat of a fish or wildlife species, cause a fish or wildlife population to drop below self-sustaining levels, threaten to eliminate a plant or animal community, re- duce the number or restrict the range of a rare or endangered plant or animal species or eliminate important examples of the major periods of California history or prehistory? Yes Maybe_ No 1 X X X X X Yes Maybe No 21. MANDATORY FINDINGS -OF SIGNIFICANCE (cont.) b. Does the project have the potential to achieve X short term, to the disadvantage of long term, environmental goals? (A short term impact on the environment is one which occurs in a relatively brief, definite period of time while long term impacts will endure well into the future). C. Does the project have impacts which are in- X dividually limited, but cumulatively con- siderable? (A project may impact on two or more separate resources where the impact on each resource is relatively small, but where the effects of the total of those impacts on the environment is significant). d. Does the project have environmental effects -X which will cause substantial adverse effects on human beings, either directly or indirect- ly? B. DISCUSSION OF ENVIRONMENTAL EFFECTS Items which follow are referenced by number to the Environmental Checklist (Section IV. A) and describe measures, if any, which can be taken by the District to mitigate potential adverse effects or provide further explanation on certain issues as to why the project will not produce any impact or only a short-term effect. Lb. Temporary disruption of the soil will occur during test hole and production well drilling, during well station construction and during trenching for the installation of the pipeline that will connect the well with the water system. These activities will result in a small quantity of surplus material which must be disposed of legally. The District will be responsible for removing and disposing of surplus material. Due to the limited scope and temporary nature of the excavation and debris removal operations, the impacts upon the environment will not be significant. 2.a. Appropriate air pollution control measures will be applied to control any temporary increases in airborne dust during construction. 3.d.&e.Water will be imported to the project site for use in drilling, and any excess will be removed by tank truck after completion of the project. Drilling fluids will be recycled throughout 12 the drilling phase of the project and will be reclaimed to be removed by tank truck. No drilling fluids will be discharged to the storm drain on site, which drains to Barron Creek. Only clean water will be discharged to the storm drain during the pumping test for the production well. Prior to beginning the pump test, all drilling and construction fluids will be suctioned from the well and removed from the site by tank truck. The initial surge of water from the pump test is expected to contain some fine sediment that will have remained trapped in the gravel envelope. To ensure that only clean water is discharged to the storm drain, the initial surge from the pump test will be discharged into a baffle tank and removed from the site by tank truck. 3.f.&g.Because this well will only be used under emergency conditions, its impact on groundwater quantities, direction of flow and quality will be negligible. The few wells in the area are used only for irrigation owing to the poor mineral quality of the groundwater. 4.a. A small amount of existing grasses, plants, and foliage will have to be removed during construction. All areas disturbed during construction will be revegetated and restored. 6.a. Temporary increases in ambient noise levels caused by construction equipment would have an insignificant short-term impact. Construction noise would not produce any long-term effect. Since the well pump will be of the submersible type (i.e., both the pump and the motor will be installed down the well under water), there will be no noise due to pumping when the well is in operation. 1 La. The project is not growth -inducing in that the well will be used only in emergency situations. 16.c. The project will provide an emergency source of water for District customers, thus improving the reliability of service within the project area. V. MITIGATION No potentially significant environmental effects are noted, therefore mitigation measures are not applicable. VI. COMPATIBILITY WITH EXISTING ZONING AND PLANS The project is consistent with existing zoning and plans. VII. NAME OF PARTICIPANTS This initial study was prepared for the Purissima Hills Water District by Berryman & Henigar, Inc., District Engineers, for the Purissima Hills Water District, and was reviewed by Geoconsultants, Inc., who are the project hydrogeologists. 13 VIII. DETERMINATION On the basis of this Initial Study, it is found that the proposed roject COULD NOT have a significant effect o the environment, and a NEGATIVET L TIO will be prepared. Dated:3 A i / P tri . Walter, General Manager 14 0�� I a a HALF MOON '—'15 CITY" ` BAY AW.1f, .Wit. POWAN ACMLOS ALMS ivrti LOS ALTOS HILLS PARK A DUBLIN YARD FREMONT SAN JOSE �Z*A Y 28 ' `LA0 AVE. \ ALTAMONT ROAD ONE STONEBR00 J roti MOODY ROAD PROSPECT ° P < a P( aIIA AVE. OAK Rid LA LOMA 5� UT�y- I PROJECT LOCATION MAP FIGURE 1 NO SCALE 28 R° aPROPOSED q' °rte R EMERGENCY �o cnw WATER SUPPLY WELL ca Ry HILL CT. ERO ROAD RN DR O FREMONT ROAD d 0�� I a a HALF MOON '—'15 CITY" ` BAY AW.1f, .Wit. 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