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• DDJC-Sharpe Work Plan-Demolitiote Building 137,Closure of Well 2 foreign materials into the well. After removal of screen interval to facilitate grout a Ary • the well head,the URS field crew will begin a through screen perforations and in o the systematic dismantlement of the existing wood- filter pack and formation. frame structure.This will include all constructed attachments,and will be completed by • The volume of required plugging demolition of the concrete foundation that is part material will be calculated prior to grout of Building 137,including the removal and mixing,taking into consideration dasing disposal of the concrete material. diameter, well depth,and applicable loss of material to the formation. Well 2.8 Using a slurry mix, URS and the drilling construction details are included i field crews will pressure grout Well 2 through attachment 2. Based on well casing screened intervals; any excess water that is diameter,the volume of grout reqt ired produced during grouting will be containerized. to fill the casing is estimated to be 2,475 It is assumed that the displaced water in the well gallons.Verification during grout will be used in conjunction with the slurry mix placement will ensure that the voli ime of design.Any well water displaced by grouting sealant equals or exceeds the volui ne of that has a pH measurement of 7.8 or greater will the casing. be contained in drums. All drummed water will be disposed at an on-depot groundwater • During grout placement, necess treatment plant. injection pressure will be calculaf d to achieve an effective seal,using specific 2.9 Grouting procedures will include the gravity of the grout mixture and following: hydrostatic head of the grout column. The amount of pressure applied depends • Well-abandonment procedures will on the characteristics of the cement • adhere to requirements set forth in slurry, slot size of the well screen, Bulletin 74-90, California Well characteristics of the filter pack at d Standards(Department of Water formation,temperature, and well epth Resources). (estimated pressure using a grout 1 veight of 16 pounds per gallon grout slur is • The slurry mix(i.e.,grout) will consist 0.83 pound per square inch per foot of a mixture of Type 11 Portland cement, below grade, plus the pressure apt lied at or equivalent(e.g.,Micro Matrix the surface to be determined by the Cement®or Pozmiz), with 3 pounds of drilling subcontractor).Pressure st all be powdered nonbeneficiated bentonite and maintained for a length of time 7 gallons of water per 94-pound sack of sufficient for the cementing mixtul a to cement; grout materials will be weighed set.The pumping of grout is antici aced with a mud scale and metered for the to occur in three stages, with each 3tage appropriate water-to-cement ratio(slurry to approximately 10 feet above each weight of approximately 16 pounds per screen interval, with pressure gallon). An accelerant will be used if maintained approximately 15-30 needed, based on site conditions. minutes at each stage. • The consistency of the grout will be • After the well casing has been bac dilled sufficient to flow through the well with grout,the protective casing iN ill be screen and into the filter pack.The grout removed and the well casing cut off at will be pumped using a tremie pipe, least 2 feet below grade and removed. which will initially be set at the bottom Additional grout will continue to be of the well and will be lifted upward as added to the casing if any settlement • grout placement occurs; the bottom of occurs. After the casing is cut off 2 feet the tremie will be adjacent to each below grade, grout will be placed in a WELL2-WP.DOC 3 9Novem er 2001