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City of Redwood City Proposal No. 03-187 September 18, 2003 Page No. 3 not confirm whether they had been installed as shown on the subdrainage plan. Shannon and Wilson's plot plan also shows two horizontal drains emptying onto the slope below the slide scarp. While we could not find these drains, we did find one clump of pampas grass in the general vicinity of where the plan shows the horizontal drains should be; however, the surface soils in the area were not noticeably wet. We also found covers for the five piezometers installed in the sidewalk area along Nob Hill Road and at the end of the cul-de-sac. These piezometers are located on Plate 1, and were identified on Shannon and Wilson's plot plan as "Borings and observation wells by others, Dec. 1966;" however, no boring logs are available for these piezometers. The first three in the sidewalk area had a small round cast metal box with a "water" cover above a vertical, plastic pipe with no top cap. Boring or Piezometer 1, in front of Lot 15, was found to be 39 feet deep and dry; Boring 2, located near the two lots' common property line, was completely filled with dirt up to the ground surface; and Boring 3, located in front of Lot 14, was open to only 14 feet below the ground surface, with the soil at the bottom of the hole being wet. A cast metal "sewer" cover was found within the street close to the locations of Borings 4 and 5 shown on Plate 1. During later site visits, on September 15 and 17, 2003, (after City personnel had removed AC pavement partially covering the boring and opened the cover) we observed the water level at Boring 4 to be about 28~A feet below the street level, with the hole open to a depth of about 4356 feet. At Boring 5, the water level was measured at 4 feet below the pavement surface, with the hole open to a depth of 4056 feet. In addition, we also observed two "City Monument" covers within the street, which agree well with the two locations (A and B) shown on the Subdrainage Plan, where a permanent 6" well casing was to be installed within the drainage gallery. We opened these two covers and at both locations found a 6-inch, steel casing with a rusted lid, but no lock as shown on the referenced Subdrainage Plan. At Location A (southern end of drainage gallery), the water was measured at 47'A feet, with the bottom of the open hole measured at 49¼ feet. At Location B (northern end), the water level was measured at about 44½ feet, with the bottom of the hole measured at 45¼ feet. This water depth contrasts sharply with that measured in the standpipes at Borings 4 and 5, which are roughly 20 feet and 55 feet, respectively, away from the well casing at Location B, and therefore brings into question whether it's the drainage gallery or the two piezometers that are not functioning properly.