Category Archives: Construction


Many people use different definitions for the term “Shotcrete”. To clarify, the International Building Code (IBC), Section 1910 clearly defines “Shotcrete” as “…a mortar or concrete that is pneumatically projected at high velocity onto a surface.” The American Concrete Institute (ACI) ACI 506 (Guide to Shotcrete) further defines shotcrete as a “wet-mix” process and “gunite” as a “dry-mix process”. Both shotcrete and gunite are defined as “Shotcrete”.

From the terms above, you can see that shotcrete is purely a method of placement. It is not a design process. Therefore, whether the pool shell placement method is shotcrete or cast-in-place, the design method is still the same. Don’t let anyone tell you there is a difference in the design. There is not!


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Measuring The Olympic Aquatic Facility Course

If you’ve been watching the Olympic swimming events, you’ve probably been noticing all the exciting finishes and as the athletes win their medals.  What you have likely missed is the tiny target marking on the edge of each lane.  This target is what the surveyor uses to accurately measure the length of the pool each day. 

Facility Design & Construction Module MAHC

The Facility Design & Construction module for the Model Aquatic Health Code (MAHC) has just been posted by the CDC today, July 20, 2012 for public comment. This module will likely have the greatest impact for the design, regulatory and construction community and not as much for operators as other modules. The deadline for public comments is October 14, 2012. Counsilman-Hunsaker strongly encourages everyone in the aquatic community to review and participate in this process.

If you are a frequent reader of Hydrologicblog, you will have seen the responses that have been compiled by Counsilman – Hunsaker and submitted as a friend of the industry through the public comment process.  If you would like to read these responses, please visit the regulation section of the blog.  We would be very interested in your comments on this section to be included in our response.

MAHC Facility Design & Construction Module Abstract

The sound design and construction of swimming pools, spas, and aquatic venues are paramount to ensuring safety of patrons who use these facilities. The Facility Design & Construction Module contains requirements for new pool construction that includes:

1) Design/construction aspects of the pool shell that include general shape, design, and slope requirements;

2) Design/construction aspects of the aquatic venue that include decks, lighting, electrical, wastewater, and fencing;

3) Design/construction aspects of specialty bodies of water and features that include spas, wave pools, slide pools, wading pools, and infinity edges; and

4) Design/construction parameters for pool equipment and under what conditions its use is acceptable including starting blocks, moveable floors, bulkheads, and diving boards.

In addition to the Facility Design & Construction module, an annex section is provides support information to assist users in understanding the background of the provisions.

The Model Aquatic Health Code Steering Committee and Technical Committees appreciate your willingness to comment on the draft MAHC modules. Click here to download comment form.

All public comments will filter back to the Technical Committee for review before the module is officially released.

MAHC Background

The Model Aquatic Health Code (MAHC) effort began in February 2005. The first industry standard was issued in 1958. In the subsequent 50 years, there have been at least 50 different state codes and many independent county codes. What was required in one jurisdiction may be illegal in another. It is clear that this historic approach is not working. Thus, the National Swimming Pool Foundation took a leadership position and provided funding to the Center for Disease Control (CDC) for the creation of the MAHC. The MAHC is intended to transform the patch work of industry codes into a data-driven, knowledge-based, risk reduction effort to prevent disease, injuries and promote healthy water experiences. To view the latest updates regarding the Model Aquatic Health Code go to

What Gets Built First – Pool or Building?

When constructing an indoor pool, we are often asked what get built first the building or pool? 

In the cold winter belt, if construction starts in the summer or early fall, contractors frequently erect the natatorium shell with its roof, before the pool is dug.  In this scenario, the dirt floor at deck level can serve as a staging area for the construction of the shell and, especially, the roof.  Once the building is enclosed, the pool can be constructed and sheltered from the weather during the winter months.  In the Sunbelt, the opposite is frequently the case. 

When the Goodwill Games was built in Long Island, the pneumatically applied concrete shell was shot against soil as a backform in the summer months.  The building was then constructed over the pool with cranes staged outside of the building, which lifted much of the material and components, including the roof trusses.  By contrast, the 109’ high roof structure at Georgia Tech was lifted by tower cranes staged on the bottom of the pool after the cast-in-place floor footings and walls were placed.  Empty areas of the floor were left for the movement and location of the tower cranes.  The floor slab voids were cast after the cranes were removed from the site. 

In the United States, the preference is to avoid below grade tunnels and full basements as a means of reducing construction costs.  In Europe and Australia, the custom and practice is to excavate to the foundation footprint of the natatorium at one time, build the cast-in-place pool shell and then finish the other spaces for storage, filtration, switch gear, possible chemical feed systems, storage: chemical storage, etc., plus other storage of dry items for the building. 

There are several options to the finished basement or even a perimeter below grade tunnel.  At Notre Dame, as well as some other pools, a below grade room was created along one of the 50M walls of the cast-in-place pool, as well as behind the pool wall at one end of the pool.  The other two walls were sealed off with concrete walls, but with an access man opening at each end of the space, which has a dirt floor and has pool piping running inside this tunnel.  Under this design, access is limited to rare maintenance and repair needs, the space does not require a finished floor, floor drainage, electric lights, or ventilation.  All of these can be provided on a temporary basis similar to sewer workers when entering a sewer for maintenance. 

The acceptance of this concept is often up to the building code officials and project.

Clear As Spring Water

The water released through automatic hydrostat valves attached to the well points under the main outlet sumps is as clear as spring water.  Most lay people expect it to be dirty because of its source in the ground.  While this may be true shortly after construction, or during construction, the gravel sub-base and soil functions similar to that of a gravity filter.  I’m sure this information can be corroborated by Andy, Bob and Scot, all of whom have emptied and cleaned pools.

Sometimes pools are stained due to construction dirt in the below grade pipes which can be washed into the pool if the tank is being filled for the first time through the surge tank and subsequently through the main drain lines.  For this reason pools are often filled through the gutters (main drained closed and gutter pipes open) so the water overflows the gutter lip and runs down the walls.   When the pumps start, the dirt in the suction pipes is drawn into the filters. Another advantage to this type of filling is that it can warm the water, flowing down the walls, several degrees inside a warm natatorium and, inversely, cool the walls and floor gradually, thereby reducing the variable between the incoming water and the warm pool shell.  As most of you are aware, cold water on a warm shell can result in thermal shock and the cracking of the pool tank. 

Another misconception by many is that ground water must be at or below the main outlet elevation to avoid foating the pool tank.  Field experience, and the laws of physics, proves that this is not the case due to the ballast weight of the concrete pool shell.  During the early years of my pool management company, I personally emptied several hundred pools. In a number of cases the automatic hydrostats opened and ground water ran into the pool for as long as thirty minutes while the submersible sump pumps were extracting the water out of the outlet basins onto the deck.  The pool at Country Hill (which was located at the top of a hill) had so much ground water one year, due to rains, that water started squirting up to 6 inches high through the expansion joint at the 5’ break when there was still several feet of water in the deep end. The hydrostats were plugged rather than fitted with check valves. There was a case at a swim club in Collinsville which was down in a small gorge with a clubhouse and tennis courts approximately thirty to forty feet above. When one of the pool cleaning crew unthreaded the brass hydrostat plug in the main drain, it shot over the three meter diving board.  For that reason everyone knew to stand aside and not be over a hydrostat when the plug was removed. 

Hopefully this specific background information will be helpful should you have an occasion to discuss the subjects with clients or operators.