SDs, DDs, & CDs -- What to do?

By Timothy Allinson, P.E.

Murray Company, Long Beach, Calif.

A few months ago we issued a project for 100% design development (DD). The project was design-build delivery and included an MEP engineer on the design team for the purpose of peer review of the design-build subcontractor documents. Prior to the issue, our executive administrator distributed criteria from the general contractor (our client) that itemized the information that should be included on the DD drawings -- an actual checklist.

After the issue, the MEP engineer did his peer review and came out with an enormous list of comments. He had reviewed the documents as if they were 100% construction documents (CDs) rather than DDs. Instead of this approach, he should have used the above referenced checklist for his review rather than generating a subjective list of what he thought should have been included in the DD submission. His comments sparked a debate over the completeness of our DD package. Thankfully, the general contractor (GC) had provided the checklist that resolved the issue, but if that checklist had not been provided, we would have likely been considered guilty of producing an incomplete DD package.

This experience inspired me to investigate a formal definition of what constitutes schematic design (SD), DD and CD, but I was unsuccessful in coming up with "the bible" on this issue. Many regular builders, such as universities, developers and GCs have their own criteria and, surely, the AIA has criteria that are available for purchase. Short of making this investment, I decided to collect information readily available from multiple entities and present it here as a reference for your future plumbing design packages.

Schematic design

Schematic design provisions may vary, depending on whether you are working on a design-bid project or a design-build project. For design-build, the requirements for design narratives and outline specifications are not usually necessary, as these have often been stipulated with the design-build RFP. In fact, design-build projects generally skip the SD phase entirely.

For design-bid projects, the SD package should generally include the following.

• Design criteria, including applicable codes, description of systems and outline specifications that establish the level of quality and performance for the project.
• An estimate of utility loads for the various plumbing systems, including domestic water, sanitary and storm drainage. Other pertinent systems should be included, such as fuel gas, medical gas and the like.
• A site plan depicting the project location and utility connections.
• Floor plans sufficient to depict the basic project space requirements and location of all major equipment. (Note: it is never too early to start coordinating chase wall requirements with the architect. The sooner the better.)
• Schematic diagrams (simplified riser diagrams) depicting basic system configurations.

Where appropriate, such as for an office building or place of assembly, it is wise to evaluate and coordinate the fixture quantities indicated by the architect with code requirements.

Design development

After the SD package has been submitted, reviewed and blessed, the DD phase begins. For design-build projects this is usually the initial phase of the project. Depending on the project size, sometimes the DD package will be issued as incremental percentages, such as 50%, 75% and 100%. For smaller projects, it might only be issued once, as 100%. Regardless, the completed DD package should generally include the following.

• Draft specifications describing the major elements of the plumbing systems. Piping materials, major equipment and standard appurtenances should be included. Detail items such as plumbing fixtures will likely not yet be determined at this phase of the project but, if they are known, they can certainly be included in the spec. If something is in doubt, it is better left out than specified incorrectly.
• Schedule sheets with standard items such as symbols, materials and the like. Equipment and fixture schedules can be included and left blank as placeholders when information is not yet known.
• To the extent that electrical requirements are known, they should be provided for the electrical engineer. Calculation sheets can be established as placeholders, with preliminary calculations for bulk loads or major pieces of equipment indicated.
• An updated site plan.
• Floor plans with preliminary bulk distribution piping and riser locations indicated. A plan should be provided for every floor or typical floor of the project. Often the architecture might not yet be defined for non-typical areas of the building; if so, these floors can be excluded. (Don't forget to continue the process of pipe chase requirements with the architect.)
• Riser diagrams further depicting the various systems, updated to agree with the floor plans. Where the architecture is still in flux it would be a waste of time to develop the risers for any such areas. Major piping can be sized where possible, and system loads can be indicated where known.

Construction documents

Obviously, the construction documents should depict the completed project. Again, for large projects the CDs are usually issued incrementally, as 50%, 75% and 100% packages or the like. Often there are disputes about what the incremental packages should include: does 50% mean that 100% of the drawings are 50% complete? Or that 50% of the drawings are 100% complete? Generally, the incremental packages will reflect something in between these two extremes.

Floor plans might be nearly complete, but since risers are one of the last things completed on any project, they are not usually completed and sized until the 100% CD submission. Ultimately, the risers should have every pipe sized with associated fixture units indicated. These sizes should then be transferred to the floor plans.

Detail sheets vary a great deal from project to project. Many engineers regurgitate standard details on every project for items that really don't require any detailing. CAD makes this regurgitation process very easy, and it makes it appear to the client that they have done a great deal of work. On our design-build projects we produce very few details -- only those necessary for non-typical or unusual project elements to be clearly understood by the guys and gals in the field. Often the details provided by the engineer are not the details required by the installer.

When finalizing a set of construction documents, engineers must remember that they are painting a picture for the contractor. The engineer should try to think in terms of, "What will the person who installs this need to know? Where are things clear and where are they unclear?" Try to resolve the areas lacking clarity to the best of your ability.

Timothy Allinson is a Senior Professional Engineer with Murray Company, Mechanical Contractors, in Long Beach, Calif. Prior to entering the design-build industry he worked for Popov Engineers, Inc. in Irvine, Calif, and JB&B in New York City. Tim holds a BSME from Tufts University and an MBA from New York University. He is a professional engineer licensed in both mechanical and fire protection engineering in various states, and is a leed Accredited Professional. Tim is a past-president of ASPE, both the New York and Orange County Chapters, and sits on the board of the Society of American Military Engineers, Orange County Post.