616 PECKS DR 2018-01-01 MF Import

1 � � � Everett School District JJ-6884 � � � 15 June 1990 Page 5 K n H 'A b H b � � � the nature of the proposed construction, we anticipate that pumped sumps and local � � interceptor trenches would adequately collect and remove water from the work site. The H �' � need for such drainage measures, as well as their location, depth, and design, shouid be � y � assessed according to conditions encountered during construction. H N O N � � � Structural Fill � y All fill placed within the buiiding areas, under paved areas and sidewalks, and in utility trenches should be placed in accordance with the recommendations contained herein. Prior to placement of structural fill, all surfaces to receive fill should be prepared as previously recommended. Structurai fill should be placed in horizont3l lifts not exceeding 8 inches in loose thickness. We recommend that the upper 2 feet of fill piaced under asphalt-paved areas . be compacted to a uniform density of at least 95 percent of the modified Proctor / . maximum dry density (ASTM:D 1557). Fill placed under slab-on-grade floors, in utility ( �,'^ trenches, under walkways, and more than 2 feet below asphalt-paved areas should be mechanically compacted to at least 90 percent of the modified Proctor maximum dry density. Utiiity trench backfill procedures should aiso satisfy local utility district 1 1�� requirements. Structural fill placed under footings should be compacted according to � the criteria described in ihe foliowing section of this report. We recommend that a �� representative from our firm be present during the placement of structurai fill to observe I �.�� the work and perform a representative number of in-place density tests. In this way, the adec,uacy of earthwork may be evaluated as grading progresses. I��j Soils used for structural fill should not contain individual particles greater than about 6 inches in diameter and should be free of erganics, debris, and other deleterious � 1�) � , materials. Given these prerequisites, the suitabiliry of soils used for structural fill Idepends primariiy on the grain-size distribution and moisture content of the soil when it is ' placed. As the amount of "fines" (that soil fraction passing the U.S. No. 200 Sieve) ��r increases, soils become increasingly sensitive to small changes in moistu�e content. Generally, soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm, non-yielding condiliun when the moisture content during compaction is more than 2 percentage points above or belo�v optimum. The soiis encountered at this site are generally silty in nature, containing at least 20 percent finas.