WORK PLANS - Laserfiche WebLink

Home Browse Search

volume of development water from each well to be 300 gallons based on previous experience installing and developing similar wells on site. Discharge water during drilling and well development shall be temporarily contained and transported to reside in DOT approved 55-gallon steel drums at a centralized location within the fenced McCormick and Baxter site. 5.6. Task 5—Well Survey. The location of each of up to four groundwater monitoring wells shall be surveyed to the nearest 0.01 foot using the state plane coordinate system(California State Plane Zone 3,North American Datum[NAD]83). For puposes of this contract,assume four wells require survey. Top of PVC well casing,top of steel monument,and ground surface beside monument shall be measured and recorded. A notch shall be filed into the top of the north-facing side of the PVC well casing to serve as a measurement point. The elevation of the well shall reference the filed notch and shall be surveyed to the nearest 0.01 foot using the National American Vertical Datum of 1988(NAVD88). All survey ties shall be made from established Government provided bench marks or from pre-existing wells with existing survey control. Survey work shall be conducted by a professional land surveyor licensed in the State of California. OPTIONAL TASKS 5.7. Task 6(Option)—Drill Subsurface Boring up to 300 Feet Depth. Under this optional task the Contractor shall drill a nominal 8-inch diameter boring with a rotosonic drill rig. Temporary steel casing shall be required to keep the bore hole open and prevent material collapse into the bore hole. Continuous soil samples shall be collected using a sonic soil core barrel advanced inside and ahead of temporary steel casing. The soil samples shall be bagged inside plastic sleeves knotted at the bottom with top and/or bottom depths written in permanent ink on each filled plastic sleeve. Samples should be undisturbed to the maximum extent practicable. The plastic sleeves containing soil samples shall be laid out beside the work area in order of boring advancement depth for easily accessible and orderly logging by the Government geologist or engineer. At no time shall soil core runs exceed 20 feet,and if recovery is less than 100 percent,much shorter core runs are expected. Soil cuttings,and soil samples after they have been logged by the Government geologist or engineer,obtained during drilling shall be temporarily contained in DOT approved 55-gallon steel drums and transported to a centralized location within the fenced McCormick and Baxter site as designated by the Government. Note: The boring(s)described under Task 6 will be completed as 4-inch monitoring wells as described under Task 7. The total number of optional borings is anticipated to be 2. 5.8. Task 7(Option)—Install and Develop Groundwater Monitoring Wells. Under this task the Contractor is to construct and install two 4-inch diameter groundwater monitoring wells inside nominal 8-inch diameter,temporarily cased borings. The boring depth will be up to 300 feet;therefore,the well, including all pertinent backfill materials,will be up to 300 feet as well. The on-site Government geologist or engineer logging the lithology of the boring will determine the final screen depth and backfill configuration; however,general backfill sequencing may include bentonite backfill below the base of the screen,and will include filter pack sand backfill within the screened interval of the well,a bentonite seal above the sand pack,and grout from above the bentonite seal to approximate land surface. Grout mix design shall be Type 1 Portland cement,5% dry bentonite per 94-1b sack of dry cement,and maximum 6 to 7 gallons water per sack cement. A steel flush-mount protective monument will be installed to protect the well casing from damage. Well screens shall be flush joint 4-inch nominal internal diameter,Schedule 80 PVC,with 0.010-inch screen slot size,ten(10)feet in length. No tail pipe is to be installed in the monitoring wells,just a threaded end plug at the base of the well screen. Riser pipe shall be of like Schedule 80 PVC. Final stick-up of the PVC casing/riser shall be approximately 0.5 feet below land surface. Centralizers shall be placed above the well screen and every 40 feet to the top of the riser pipe.