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ON -CALL ENGINEERING SERVICES Wntor ResoVrcea-0010A static water level have remained consistent; and/or the well begins to pump sand and/or gravel pack, or even displays large amounts of entrained air in the pumped discharge. The causes for these observed conditions can be due to many reasons; Including; pump, motor, and/or electrical problems, resulting in decreased production rates; bioiogioal fouling of the perforations and gravel pack, resulting In plugged conditions, thereby decreasing the production rate and specific capacity and deepening of the pumping levels, and even loss of pump efficiency; and/or development of holes in the well casing and/or enlargement of the perforations, resulting in the production of sand. When considering well rehabilitation, site -specific data from the Well in question needs to be evaluated to determine what could be causing the observed conditions, Therefore, it is Imperative to obtain and review available data on both historic and current values for: static and pumping water levels; water quality; specific capacity, well construction records; previous well rehabilitation work; production rates; and video logs, etc. Only through, review of such data by qualified hydrogeologists can the potential reasons) for the decreases in well performance and the Identification of rehabilitation steps be defined, it is understood that the subject of the Santa Ana Water Project is reported as being 3p years old and is currently producing sand. Because It is constructed of low carbon steel, the casing may be reaching near the and of Its useful life and further operations may lead to complete failure, e.g., by a potential casing collapse, However, the life of the existing well could be extended somewhat longer by the installation of a full, stainless -steel liner casing in the well and this is the prime recommended course of action that can now be undertaken on the well. The project can be approached in one of two ways by the City. An initial approach, and one that is less efficient, is to conduct this initial work as part of a prepared set of Technical Specifications where all rehabilitation options are included. However, a second, and more efficient approach, would be for the City to contract with a well rehabilitation company to conduct initial Investigatory operations on the well to determine the Current downhole conditions In the wall. This would Include conducting an Initial short-term pumping test to obtain the current, pre -rehabilitation specific capacity of the well, This would be immediately followed by removing the pump and running a down well video survey to determine the observable condition of the casing and the perforations, and depth of the sand in the well. This would be a preferred approach, because by determining the current condition of the well, a set of Technical Specifications can be prepared with the necessary rehabilitation operations already provided. This is the approach that Tetra Tech is using on the Well No, 32 Rohabllitation Project for the City. The tasks for this preferred initial approach would be as follows: Following removal of the pump motor, column and bowls from the well, inspect and measure all apparatus (conducted by the contractor in the field and at tile pumping contractor's shop). 2. Sound the bottom of the casing to dotormine the current amount (and type) of sediment fill and then bail that sediment from the bottom of the casing; examine the collected sediments and possibly conduct laboratory analysis. Check carefully for the possible presence of gravel pack and/or formation sand in the balled material, 3, perform a current video survey of the well to determine the depth to which sand has filled the well; check for possible holes in the casing, and the possible extent of plugging of the perforations. City of Santa Ana - b - TETRA TECH