Loading...
HomeMy WebLinkAbout01/05/1993, 4 - EXPLORATORY NON-POTABLE WELL AT WATER RECLAMATION FACILITY1IIINI11I11 QUINfI MEETING DATE: 1W� 11 city Of Sark �aIS OBISPO January 5 1993 so COUNCIL AGENDA REPORT 0� FROM: John Moss L ',.( Prepared By: David Pierce Acting Ut' ities Director Reclamation Coordinator SUBJECT: Exploratory Non - Potable Well at Water Reclamation Facility RECOMMENDATION By motion, approve plans and specifications for "Non- Potable Well at Water Reclamation Facility, City Plan Number T -35L" and authorize soliciting of bids and contract award by the CAO, if the lowest responsible bid is within the Engineer's cost estimate. DISCUSSION This project consists of drilling three small diameter holes to determine the most promising location for a well and then drilling an exploratory well to test the production potential. This work needs to be accomplished at this time to confirm the yield of the well so that the impacts of a permanent well can be analyzed in the Water Reclamation Project EIR. This is not a recommendation to actually operate this well at this time. The recommendation is merely to evaluate the potential in order to scope the project for the EIR. Preliminary design work on the Water Reclamation Project has identified that a significant limitation to amount of reclaimed water that can be used for irrigation will be the amount of water that can be provided to meet the customers peak demands. The flow through the Water Reclamation Plant will be fairly constant during dry weather. The number of customers that may be connected to the system will be limited by the amount of water that can be provided to meet their peak demand in August. If the peak supply can be increased during the month of August, additional customers may be served and they can continue to be served using reclaimed water only during the lower demand periods. The additional water for peak supply can be supplied from seasonal storage of reclaimed water or by obtaining water from another source. Seasonal storage requires large land areas for ponds or tanks which may be susceptible to algae and odor problems and will be very costly. Therefore well water is proposed as a readily available cost effective additional source. Although well water is being drawn from the same ground water basin as our potable water supplies, there is a net reduction in the need for potable water for irrigation because the addition of this water during the peak demand periods allows an increase in the use of reclaimed water during non -peak periods. Since the main users of reclaimed water would be using well water or potable water for irrigation if the reclaimed water were not available this will produce a net reduction in demand for potable water.. ������i� ►►►�IIIIIII�I��� °� ►��II city Of san ,.-.is OBISPO COUNCIL AGENDA REPORT Well Project T -35L page 2 Without a well it will be possible to deliver up to 1480 acre feet of reclaimed water per year for irrigation. Using a 200 gallon per minute well during August, it will be possible to provide a total of 1600 acre feet of water per year for irrigation. This will include 35 acre feet of well water and an additional 86 acre feet of reclaimed water. This roughly translates it; for every gallon of well water used to supplement the program peak needs, an additional 3 gallons of reclaimed water can be sold. On the following graph, the bars depict the reclaimed water available from the treatment plant (monthly variations reflect the length of the month), the - +- line depicts the water useful for irrigation without a peaking well, the - *- line depicts the water useful for irrigation with a 200 gallon per minute peaking well, and the darkened portion of the bars depict the increase in reclaimed water that is useful for irrigation with the peaking well. Note that the additional water available for irrigation is reclaimed water except for August and a portion of June. 300 250 200 a a L6 150 a L U 100 50 M Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun ® Available —+— No Well A 200 gpm WATER RECLAMATION PLANT EFFLUENT AND IRRIGATION WATER SUPPLY �����►r►►i�uiIIIIIIIJP�► ��lllll Clay Of San _JIS OBISPO COUNCIL AGENDA REPORT Well Project T -35L page 3 The non - potable well can be located on City owned property, adjacent to Interstate 101 near the ponds. This site is an excellent area for groundwater, and due to Health Department restrictions and possible water quality problems, is unsuitable for a potable water well. FISCAL IMPACT Engineer's estimate for the installation of this exploratory well is: Drill 3 pilot holes $ 61000 Drill & test exploratory well 17,000 Contingency @ 9% 2.000 Total Engineer's estimate $25,000 A total of $2.35 million was approved for groundwater water development, phase III (1989 -91 Financial Plan Supplement and Approved 1990 -91 Budget, page H -16). ALTERNATIVES 1. Construction of seasonal reservoirs. To replace a 200 gallon per minute well would require 40 acre feet of storage. To use all available reclaimed water for productive irrigation would require 1300 acre feet of storage. This alternative would require significant land for storage pond siting and would be costly to construct and maintain. This alternative is not recommended. 2. Limit the distribution of reclaimed water to those customers whose needs can be fully met by available reclaimed water from the reclamation plant. This alternative would reduce the amount of water available for reclaimed use by approximately 120 acre feet /year. This alternative is not recommended. Plans and Specifications are available for review in the City Council office.