Generic or Project Specific Engineering?
Generic structural engineering fills a void in the concrete swimming pool construction market by providing cost effective "ready made" and "off the shelf" engineering. These plans are sufficient for most tract home pools with a flat yard and no surcharges.
Project specific engineering is structural engineering that has been designed FOR YOUR SPECIFIC PROJECT. This means that the experts have consulted with each other and have designed something that will economically function on your site.
The Dangers of using Generic Engineering
The publishers of generic structural engineering provide a catalog or on-line listing of their various plans and construction details. This allows the pool builder to select the products that they need & rapidly receive the plans. Therein lies the whole problem... the pool builder SELECTS the engineering, the strengths and what is required.
Though the plans are engineered, each is contains details unique to the soil conditions. Standard plans are designed to accommodate various types of expansive soils. Many contain three to four various steel schedules, based upon the soil condition on the construction site. Who determines the soils conditions on the site and the resulting strength of shell to use? The pool builder, of course.
Without obtaining a soils report (aka: geotechnical report) prior to construction, then your pool builder will select the appropriate (or inappropriate) engineering. There is ABSOLUTELY NO WAY to determine the soil conditions without a soils report.
Generic mail order plans also do not take into consideration the "site conditions" on a construction project. The structural engineer has not reviewed the topography of the site to determine if any surcharges are present. A surcharge is something that can potentially place stress upon the pool structure. Surcharges can be nearby up slopes, down slopes, buildings, structures, lakes, retaining walls, surf, snow, wind or even seismic events.
Without a structural engineering review of the project plan, soils report, topographical map and site images, the responsibility of identifying these surcharges is left to the pool builder. Even if they do identify potential surcharges, do you really want them determining the amount of surcharge? Are you confident that they identified ALL of the potential surcharges?
Generic engineering is designed to be a catch-all for all geographic regions where the mail order engineering firm is licensed. This means that the plans may include structural elements that are not required in your local. This all translates to unneeded additional cost for the buyer. The plans may also omit items that may be required by local code or ordinance.
Additionally, these plans are only designed to meet the MINIMUM standards. Though industry standards often utilize 4,500 or even 5,000 PSI concrete, these generic plans oftentimes only specify 2,500 PSI concrete.
Why? Because most pool builders who are utilizing mail order plans are cost conscience. 5000 PSI concrete costs more. Concrete exceeding 2500 PSI also requires that the placement of the concrete be inspected by a special deputy inspector, and in some regions, a quality assurance testing laboratory. Again, additional costs. But why wouldn't you want these workmanship guarantees and quality assurances?
Correctly Utilizing Generic Engineering
If you plan on utilizing generic mail order engineering, then there are some things that must occur:
1. A soils report for the construction site must be provided to the structural engineer. Test borings must occur in the proposed locations of construction.
2. The structural engineer must be provided site images, a topographical map and proposed project layout.
3. The structural engineer must provide a letter or notations on the plans that they actually reviewed the soils report & make reference to the Soils Engineering Report, date and author.
4. The soils engineer, then must review the generic mail order structural engineering and write a letter stating that they have reviewed the structural engineering and that they agree that the plans meet or exceed the requirements for the site.
5. The structural steel should be inspected by the structural engineer to verify that the plans were followed. This can be an in person inspection or through digital photographs. An "inspection letter" should be obtained, stating that the structural engineer has reviewed and approved the steel placement.
6. Minimum concrete strengths should be 4,500 PSI.
7. An inspector should be present during all gunite/shotcrete placement. Samples should be sent to a testing lab to verify that you're getting what you paid for.
Why not use Project Specific Engineering?
Since project specific engineering requires that the same steps be followed as using generic engineering correctly, why not just obtain project specific engineering?
GOOD QUESTION !
Paolo Benedetti Aquatic Artist, Consultant & Construction Defect Expert Witness
"Creating water as art."™
Aquatic Technology Pool and Spa