1.1 This specification covers the manufacture and purchase requirements of products used for the assembly and construction of circular precast reinforced concrete manholes used in sewer and water works. 1.2 Part I, Sections , of this specification presents general requirements and requirements that are common to each precast concrete product covered by this specification. 1.3 Part II of this specification presents specific requirements for each manhole product in the following sections: Product Section Grade Rings Flat Slab Tops Risers and Conical Tops Base Sections Steps and Ladders Note 1 Future products will to be included in Part II in a future revision of this specification. 1.4 A complete metric companion to this specification has been developed, Specification C 478M; therefore, no metric equivalents are presented in this specification. Note 2 This specification is a manufacturing and purchase specification only and does not include requirements for backfill, or the relationship between field load conditions and the strength requirements of the manhole products and appurtenances. Experience has shown, however, that the successful performance of this product depends upon the proper selection of the product strength, type of foundation and backfill, and care in the field installation of the manhole products and connecting pipes. The owner of the project for which these products are specified herein is cautioned to require inspection at the construction site.