4202 CRESCENT AVE 2016-01-01 MF Import

Sep 2B 00 12: 36p GEOTECH COHSULTHnTS, InC. [4251747-8561 p, 5 I I I Leggcy Development JN 00376 � September 27.2000 Page 5 Retainlnn Wall Backfill � Backfill placed behind retaining or foundetion walls ahould be coarse, hee{Jraining � atructurel fill containin�no on3anip. This backfill should contain no mora than 5 percent siR ' or day particles and have no grave! greater than 4 inches in diameter. The perceMage of particles passing the No. 4 sieve should be between 25 and 70 percent. The native sifl soil should not be used as free-draining backfill far this project. The purpose of these backfill requirements Is to enaure that the design criteria for a retaining wail are not exceeded because of a build-up of hydrostatic pressure behind the watl. The top 12 to 18 inchee of the backfill should consist of a compacted, relatively impem�eable aoil or topsal, or the surface should be paved. The ground surfac� must also slope avray from backfiNed walis to reduce the potential for surface water to percolate into the backfill. The section entitled GENERAL EARTHWORK AND S7RUCTURAC FlLL contains recommendaUons rn�arding tt�e placemaM and compactfon of�huctural fiH behind retaining end toundation wails. The above recommendations are not intended to waterproof the below-grade walls. The pertormance of subsuriace drainage syatems will degrade over time. Therefore, , waterproofing should be provided whero maist condfions or some seepage through ttie walls are not axeptabla fn the futu2. This typfcally includes limiting cold-joir�ts and wall penetrations, and using bentonite panels or membranes on the oubide cf the walls. Applying a thin coat of asphalt emulsion is not considered waterproofing, but will only help to prevent moisture, generated from weter vapor or capillary ection, from seeping through the concrete. . SLABS-�N•GRADE The building floors may be constructed as slabs-on-grede atop firtn, non-organic, native soil or atructurel fill. The subgrade sol must be in a firtn, non-ylelding condition at the time of slab constructian or undersleb fili placement. My soft areas encauntered should be e�ccavated and replaced with select, imported strudural fill. All slabs-orrgrade should be underlein by a aapillary break or drainage layer consistlng of a minimum 4inch thidcness of coarse, iree�draining strudural fiil with a gradation simaar to thet discussed in PERMANENT FOUNDATION AND RETAINING WAI.LS. As ►mted by the American Concrate Institute (ACq in Sedion 3,2.3 of the Guides for Concrete Floor and Sla6 Sbudures, proper moisture protection is desirable immedfetely below any on-grade slab that wiil be covered by tile, wood, carpet, impertneable floor coveringc, or any moisture-seneitive equipment or producb. ACI also notes that vapor retarders,such as 6-ml visqueen, are typically used. A vapor retarder is d�ned as a material with a permeance of less than 0.3 US pertns per square foot (ps� per hour, as determined by ASTM E 96. It is possible that �oncrete admixtures may meet this specfication, although the manufacturers af the admiutures should be consuRed. However, if no potential for vapor passage through the slab is desired, a vapor banier should be used. A vapor barrier, as defined by ACI, is a product wkh a water transmission rate of 0.00 pertns per square foot per hour when tested in accordance with ASTM E 96. Reinforced membrenes having sealed overlaps pn meet this requirement. Addidonaily, ACI (Section 4.1.5) recommends that a minimum of 4 incfies