Agmt25 Casey Construction, Inc. - Laserfiche WebLink

Browse Search

TRENCHING & BACKFILL 02 2020-5 2.04 SPECIAL REQUIREMENTS FOR SELECT BACKFILL IN BAY MUD CONDITIONS A. In areas where Bay Mud is prevalent, there are two distinct types of soil material present, Bay Mud and Imported Fill Material. Bay Mud consists of very soft, cohesive, clayey material, and it may be encountered from 1 to 4 feet below grade, depending on location. (At Redwood Shores for example, Bay Mud generally occurs at elevation 100). Excavated Bay Mud may be either segregated and hauled off the site, or dried and conditioned for placement back into the trench per Paragraph 3.07 of this specifications section, at the Contractor's option. B. The existing imported fill may be salvaged and used for backfill if it meets with the requirements of select backfill, per Paragraph 2.03 of this specifications section. C. Suitable excavated Bay Mud from trenches may be conditioned by aeration and used as backfill. To accelerate drying to optimum moisture content for compaction as backfill, spreading, disking or harrowing may be required. 2.05 SUBDRAIN MATERIAL A. Where required for trench drainage and for subsurface drains, bedding shall conform to the requirements of Class 1, Type A Permeable material per Section 68 of State Standard Specifications. 2.06 CONTROLLED DENSITY FILL (CDF) (in trenches) A. Controlled density fill will be accepted in lieu of the standard backfill specifications. It shall be mandatory in trenches eight (8) inches wide or less where the prevention of subsequent settlement after placement of backfill is required. CDF shall conform to the following requirements: 1. Strength Requirements a. Non-structural CDF that can be excavated by hand shall produce unconfined compressive 28 day strengths from 50 psi to a maximum of 150 psi. CDF that is to be excavated by hand shall contain aggregate no larger than 3/8" top size nor shall the 3/8" aggregate comprise more than 30% of the total aggregate content. 2. Materials a. Cement shall meet the standards as set forth in ASTM C-150, Type II Cement. b. Fly ash shall meet the standards as set forth in ASTM C-618, for Class F pozzolans. The fly ash shall not inhibit the entrainment of air. c. Air entraining agent shall meet the standards as set forth in ASTM C-260. d. Aggregates need not meet the standards as set forth in ASTM C-33. Any aggregate, producing performances characteristics of the CDF, for any