Implementation design is the process of turning a plan established in basic design into construction-ready drawings.
Literal
Implementation-design [definitional-とは] basic-design [with-で] decided plan [object-を], construction [subject-が] can-do drawings [to-に] write process is.
~とは defines a term: 'X means...' 実施設計 (implementation design) and 基本設計 (basic design) are industry-specific architecture/engineering terms. 工事ができる図面 uses a relative clause with the potential form: 'drawings from which construction can be done.'