Category Archives: Construction

Modern Swimming Pool Concrete and It’s Ancient Past

Beneath the water and under the plaster and tile finish lays the fundamental element in most swimming pools: concrete. It has been used to reinforce a pool’s structural shell for over 2,500 years; the Ancient Romans were the first to use it in their baths. But what is it about concrete that has kept it in use throughout history and into the modern day?

Concrete is made up of three basic components: water, aggregates and Portland cement.  Water hydrates the cement and provides the exothermic chemical reaction which begins the hardening process.  The amount of water in a concrete mix can vary, but in general, the lower the water/cement ratio, the stronger the resulting material.  Contrary to popular belief, concrete and cement are not the same thing; cement is actually just a component of concrete.  The cement and water form a paste that coats the aggregate and sand in the mix. That paste hardens and binds the aggregates together.  The aggregates vary based on the mix design, but usually include small, medium, and large aggregates such as sand, gravel, and crushed stone.

Other than stone, the aggregate category also includes additives which alter the properties of the concrete. Some additives accelerate the concrete setting time, while others slow it down according to the designer’s needs. Two common additives are Fly Ash and ground granulated blast furnace (also known as “Slag.”) These common pozzolans react with calcium hydroxide to improve the workability of concrete, improve surface finish, and reduce the heat generated by setting concrete.

The American Concrete Institute (ACI) has extensive documentation on the use of both Fly Ash and Slag in concrete mixes.  As these additives tend to be less expensive than cement (and may be used as cementitious replacements up to 50%), they can be tantalizing options with significant budgetary implications.   Fly Ash and Slag may even be used interchangeably if one is not available.

It is important to note that while up to 50% of cementitious material may be substituted with Slag (per ACI standards), a rule of thumb in pool structural design is to cap the replacement at 15%, as the long-term performance of the concrete may be affected.

From purely a structural performance perspective, with an eye to serviceability and durability, the ACI does not have any issues the use of pozzolans.  However they will affect the concrete, something contractors need to be aware of prior to construction.  Additionally it is critical that the concrete batch plant is aware of the application of the concrete prior to determining the mix design.

How does all of this affect swimming pools?  The use of pozzolans in swimming pool concrete has been used for many years.  Regardless of the pool’s intended finish (tile, plaster, or paint), it is important to follow the manufacturer’s recommendations for finish application; such as ensuring the concrete is clean and free of debris.

As always, please contact a structural engineer for any structural design solution.  For more information on swimming pool concrete or the application of a pool shell finish, please refer to following online resources:

Portland Cement Association – http://www.cement.org/index.asp

National Plaster Council – http://www.npconline.org/

The Tile Council of North America – http://www.tcnatile.com/

All Stories

What To Do When Your Pool Leaks

A leaking pool is a problem…for everybody. How do you find the leak or leaks, and then how do you fix the problem?

Following a plan can often reduce time and frustration.  A good strategy for finding one leak is the following:

1.      Identify the most likely sources of a leak in a pool:

a)  A crack or hole in the shell

b) The expansion joint and the water stop is broken and the sealant is compromised

c) Honey combing (tiny holes) in the concrete around fittings

d) An underwater light conduit broken or unglued

e) A leaking seat at a hydrostatic relief valve

f) A failure in the underground piping

2.      Testing for leak:

  •  Step one: At closing time, mark the normal operating water level.  Operate the filter pump all night and then mark and measure the loss of water 12 hours later the next morning.
  •  Step Two: At closing the following evening, repeat the same as above except turn off the filter pump. The next morning mark and measure the loss of water.

a)  If the water loss is the same, whether the filter pump is running or not, the leak is in the pool shell, and at one or more probable sites identified as in a-e above.

b)  If the water loss is greater when the filter pump is operating it suggests the leak is in the pressure piping.

c)  If the water loss is less when the filter pump is in operation, it suggests that the leak is in the suction piping i.e. the suction in the pipe draws groundwater into the pool or mud impacts a crack in the pipe, thus reducing the loss of water.

d) If a leak in the pool shell is identified as large or small, the next step is to confirm the location. The most common is to use food-coloring concentrate or crystal violet with scuba or mask and snorkel.

e) Modern technology provides professional leak detection contractors.

f)  If the leak can be diminished by temporary underwater repairs to the pool shell or piping, that may be the best tactic until the end of the outdoor season. If in an indoor pool, a shutdown will need to be scheduled to make repairs.

This was shared by Joe Hunsaker with Aquatic Professionals in 2005.

 

ADA Update

The revision to the Americans with Disabilities Act was signed into law on July 26, 2010, published in the Federal Register on September 15, 2010, and went into eect on March 15, 2011. Full compliance with the regulations was originally slated for March 15, 2012.

In January, 2012, the Department of Justice released a Technical Assistance Bulletin in an attempt to clarify several areas of confusion regarding swimming pool accessibility, specifically, the use of swimming pool lifts.

This document discusses requirements for both Title II (local and state government owned) and Title III (privately owned) facilities.

In providing access to their aquatic programs, this document gives Title II facilities the option to either use a fixed pool lift, or equipment such as a portable pool lift, providing the lifts met the requirements of the regulations. The document also states that sharing lifts between pools is not be permitted unless providing a lift at each pool would create an undue burden. The document also stipulates that accessible features must be available whenever the pool is open to the public.

Title III facilities were instructed that barrier removal can be accomplished by the use of a fixed lift or other means of access that conform with the regulations. If the installation of a fixed lift is not readily achievable, a facility can then consider alternatives, such as the use of a portable lift, as long as the lift conforms to the regulations.

This document was the first mention of any distinction between fixed lifts and non- fixed lifts dating back to the mid-1990’s and the initial study conducted by the National Center for Accessibility at Indiana University, which laid the groundwork for the eventual ADA regulations. As a result of the uproar generated by the January document, Allison Nichol, the Chief of the Disability Rights Section of the Department of Justice, sent a letter to the Hotel and Lodging Association to attempt to clarify the confusion. In this letter Ms. Nichol states:

The 2010 Standards apply to “fixed” or built-in elements. A “fixed” element is one that is attached to a covered building or facility. Therefore, for an existing pool with less than 300 linear feet of pool wall, for example, removing barriers will involve providing one accessible means of entry, meaning a built-in or “fixed” pool lift or a sloped entry that complies with the 2010 Standards to the extent that it is readily achievable to do so (larger pools with 300 or more linear feet of pool wall are required to have two accessible means of entry, with at least one being a pool lift or sloped entry). If, in our example, an entity chooses to use a lift complying with the 2010 Standards that is removable or otherwise designated as “portable,” it may do so, so long as while the lift is provided at the pool, it is axed in some manner to the pool deck or apron.

If installation of a fixed lift or sloped entry is not readily achievable, then a public accommodation may consider alternatives such as use of a portable pool lift that is not axed to the pool facility but incorporates features that in all other respects comply with the 2010 Standards, or the public accommodation may consider other readily achievable accessible means of entry, such as a transfer wall or pool stairs. However, the 2010 Standards’ emphasis on the provision of a lift or a sloped entry recognizes the fact that many people with mobility disabilities rely more heavily on these means to independently enter and exit a pool.

Rather than clarify the situation, this rather ambiguous comment added more confusion. Especially the passage that seemingly now requires portable lifts to be attached to the pool deck. I contacted the DOJ and asked them to provide some guidance on what they considered an acceptable way to attach a portable lift to the deck, for example, would they allow wheel clamps. To date, despite numerous calls and emails, I have received no reply to this question.

The furor and confusion created by these new interpretations of the regulations led to a great deal of public backlash, including legislation proposals in both houses of Congress to challenge them. In fact, a Congressional hearing was conducted in the House of Representatives to investigate the issue. The central question of the legislative concern was whether or not the Department of Justice was overstepping its authority and engaging in rulemaking without following the proper steps, including seeking public comment, prior to doing so.

Because of this uproar, the DOJ extended the compliance date for swimming pools into May, 2012. On May 24, 2012 it issued a follow up Technical Assistance Document. The language in the follow up document was basically the same as the January Bulletin, with this addition:

If you have purchased a non-fixed lift before March15 th that otherwise complies with the requirements in the 2010 Standards for pool lifts (such as seat size, etc.), you may use it, as long as you keep it in position for use at the pool and operational during all times that the pool is open to guests. Because of a misunderstanding by some pool owners regarding whether the use of portable pool lifts would comply with barrier removal obligations, the Department, as a matter of prosecutorial discretion, will not enforce the fixed elements of the 2010 Standards against those owners or operators of existing pools who purchased portable lifts prior to March 15, 2012 and who keep the portable lifts in positon for use at the pool and operational during all times that the pool is open to guests so long as those lifts otherwise comply with the requirements of the 2010Standards. Generally, lifts purchased after March 15, 2012 must be fixed if it is readily achievable to do so.

In addition, the compliance date for existing facilities was pushed back to January 31, 2013. New facilities and facilities undergoing renovations must adhere to the March 15, 2012 compliance date.

It is very likely that the final outcome on the issue of fixed and non-fixed will be decided in a courtroom, sometime after January 31, 2013. In the meantime, manufacturers of portable lifts are providing adaptor kits that allow these lifts to be fixed to the deck. In most cases, these attachment kits are designed so they will not require any bonding.

For now, here is the status:

•  Every pool has to be accessible. Lifts cannot be shared between pools, unless providing a lift at each pool would create an undue burden on the facility.

•  Lifts should be in place and ready for use whenever the pool is open.

•  Lifts should be attached to the pool deck, unless it is not readily achievable to do so. If this is the case, a lift that is not attached to the deck may be used.

•  The owner of a facility makes the decision as to what is readily achievable for that facility.

•  New facilities and those undergoing renovations must fully comply with the regulations as of March 15, 2012.

•  Existing facilities must comply with the regulations before January 31, 2013.

Built on Evidence

The MAHC Facility Design & Construction Module aims to fill holes other codes don’t address and provide scientifically based best practices. See where the recommendations have the largest impact.

The following article was published in Aquatics International in the November / December 2012 Issue

The goal of the Model Aquatic Health Code is to codify scientifically proven data in the aquatics industry. When that is not possible, each technical committee is to look first at current best practices in the industry and identify areas within each module that would benefit from future scientific studies and research. Topics within the Facility Design & Construction Module that tend to either deviate or expand upon many published codes at the state and local level include the required depths for starting blocks and diving boards; overhead and underwater lighting; deck areas within an aquatics facility; the design requirements of natatorium structures and support spaces; and several pool features such as infinity edges, bulkheads, and movable floors that are not addressed in the majority of today’s current standards. All recommendations apply to new construction.

The current draft of the FD&C Module defers to the applicable governing body for required water depths and envelopes necessary for the use of starting platforms and diving boards. Today, there are different requirements between USA Swimming, NFSHSA, NCAA and FINA, as well as state and local codes. For facilities that are not under the umbrella of one of these competitive swimming and diving governing bodies, MAHC writers took the position that the most conservative requirements would apply.

Design requirements for lighting — overhead and underwater — was a focus of particular importance. Historically, underwater lighting requirements for swimming pools have been regulated using a watts per square foot of pool surface area measurement. In an attempt to steer aquatics in a direction more consistent with widely recognized electrical units of measurement, equivalent units of initial lumens and efficacy are used alongside watts per square foot. Also, conventional regulations require one level of underwater lighting applicable to all types of pools. The FD&C Module highlighted the different requirements for indoor vs. outdoor pools, as well as pools that accommodate diving vs. those pools that do not. Minimum overhead lighting levels also are required to be met based on whether the pool is indoors or outdoors and whether it’s intended to operate outside the limits of dawn to dusk. It is acknowledged that many of these overhead and underwater lighting standards derive, at least in some part, to historical best practices. It is recommended by the Technical Committee that future studies be conducted to determine minimum lighting requirements based on water depth, hours of operation, overhead lighting design, location and the impact that these variables have on each another.

Another subject related to lighting that was heavily analyzed was glare. In the end, while it is widely acknowledged that glare on the pool surface can provide concern for lifeguarding, it was a tremendously difficult topic to regulate from a code perspective. Instead, recommendations were provided in the annex to the design community to help mitigate this issue. For instance, careful consideration should be given to the placement of windows and skylights in a natatorium. Natural light from directly overhead is less likely to create glare than light through windows at the sides and ends of the pool. Control of glare from artificial light is more likely if the angle of incidence of the main light beam is less than 50 degrees from straight down. Diffuse or indirect light sources also can help to minimize glare.

The FD&C Module also expands upon the traditional definition of pool decks found in most current regulations. Most codes tend to define the term “deck” as a general term that applies to all areas surrounding a pool, and typically governs minimum widths and slope requirements — and little else. From a useability standpoint, the Technical Committee thought it was valuable to separate the terms “perimeter deck,” “dry deck” and “pool deck” from one another. Perimeter deck applies to the minimum required hardscape surface area surrounding the perimeter of the pool. Pool deck is defined as the hardscape surface areas beyond the perimeter deck that is regularly trafficked by wet bathers. Finally, dry deck refers to all pedestrian surface areas within the pool enclosure that are not subject to frequent splashing or constant wet foot traffic (not including landscaped areas, which are addressed and regulated separately). The main purpose for separately defining these areas is to create conditions for acceptable deck materials and finishes in various areas.

The Technical Committee also recognized that a standard minimum slope requirement often cannot be sufficient in and of itself to ensure that no standing water is allowed on the deck. The preponderance of existing codes and established standards were distilled to create minimum slope requirements for smooth finishes (such as ceramic tile and lightly broom-finished concrete), moderately textured finishes (exposed aggregate and medium broom-finished concrete), and heavily textured finishes (brick and heavily broom-finished concrete). It was noted that there is an inherent conflict in the sloping of decks. Steeper slopes provide more construction tolerances and surety in conveying water, particularly in active soil conditions. Shallow slopes are required to meet accessibility guidelines — particularly for cross slopes. It is the intent of the FD&C Module to encourage positive and proper drainage without running afoul of accessibility guidelines.

Many aspects of the unique characteristics of natatoriums and their support spaces are not specifically addressed by the International Building Code, ASHRAE or other existing standards. The FD&C Module fills these gaps so that sound design and construction practices are required for aquatics facilities. It is not intended to be construed as providing relief from applicable requirements in fire-, mechanical-, electrical- and building codes. But the impact of pool chemicals, their corrosive nature, pool combustion equipment, ventilation requirements and the like on typical aquatic environments are all critical design and construction requirements that benefit from being in a standard such as MAHC.

Finally, the FD&C Module adds regulatory parameters for several commonly found elements within today’s pools that are not addressed by the overwhelming majority of current standards. These include pool design elements such as wing walls and infinity edges. Wing walls often are misinterpreted to be “deck” even though they are not intended for foot traffic, but defined as such can trigger minimum-width requirements, drainage and more when they are merely intended to reconcile floor slopes and termination of in-pool elements such as entry stairs. Infinity-edge pools often are required to have decking around 100 percent of the perimeter, which inhibits a traditional “infinity” effect and does not necessarily have to impact life safety.

Pool equipment such as bulkheads and movable floors can seldom be found, if at all, under current pool regulations in the United States, but the MAHC writers thought it was important to regulate these for safety. So potential entrapment issues are addressed under “bulkheads”; and regulations for movable floors are implemented during installation and operation, such as speed of travel, barriers at floor slope transitions, and inability for bathers to access underneath the floor structure at any time.

Ultimately, the FD&C Module strives to merge scientifically proven data into a codified standard, along with industry best practices, and historically overlooked areas of regulation in the ever-changing world of aquatics facility design and construction.

Minimum Water Depths Under Starting Blocks

On July 20, 2012, the Facility Design and Construction Model for the Model Aquatic Health Code (MAHC) was posted for public comment due October 14, 2012.  In section 4.8.3.3. a single sentence could change the industry standard for minimum depths  under starting blocks to 6 feet and 7 inches for a distance of 20 feet.  This could have a significant impact on swimming pools around the country and industry professionals are encouraged to participate in the public input process.  In order to make an informed decision, the following data is offered for consideration. 

Competitive swimmers execute headfirst dive entries from starting blocks into pools where water depths can vary. If the swimmer’s head strikes the bottom of a pool, this could result in damage to the cervical vertebrae, thus may result in quadriplegia. This was a significant topic of conversation in the industry in the early 1980s when a varsity swimmer at a university was injured in practice. Before 1970 this was unheard of, but in the early 70s, goggles were introduced and different methods of completing racing dives were developed to maximize speed and minimize the potential for losing goggles.  

In prevention of Cervical Spinal Injuries (CSI), a cohesive plan currently does not exist for a minimum uniform water depth, which would lessen the likelihood of catastrophic tragedies. “No Diving” signs are posted when the water is less than five feet deep in some states, and four feet in others. There is still more inconsistency. What is the right depth for balancing safety and function for underneath starting blocks? Moreover, should we build all-deep water pools? What depth? And what about recreation swimmers?  

Here’s the Confusion

Up until the early 2000s the industry standard water depths were in the 3 feet 6 inches to 4 feet range. November 2001, the National Federation of State High School Associations (NFHS) changed minimum water depths from 3 feet 6 inches to 4 feet. USA Swimming followed suit with a note that teaching off a starting block shall be limited to 6 feet water depth. 

Policy makers, swimming pool rulebooks, and state swimming pool codes still lack research in regard to water depth requirements under starting blocks. Moreover, water depth requirements under starting blocks in governing bodies’ rulebooks not only conflict with one another but often conflict with state statutes, which may in turn conflict with local county and municipal ordinances.  

The following shows a variance among the four aquatic governing bodies, as well as the YMCA and the American Red Cross, in regard to water depth for headfirst entries. 

Federation Internationale DE Natation (FINA): 4 feet 5 inches.

National Collegiate Athletic Association (NCAA): 4 feet.

National Federation of State High School Associations (NFSHS): 4 feet.

USA Swimming and US Masters Swimming: 4 feet for racing, 6 feet for teaching.

YMCA: 5 feet.

American Red Cross: 9 feet.

 

The Research

The Counsilman Center for The Science of Swimming completed a study in 2011 on racing start safety published in the International Journal of Aquatic Research and Education.  Joel Stager, Director reports the water depth needed to prevent contact with the bottom of the pool that could result in injury is well beyond 6 feet 7 inches and the critical link to safe starting block starts is education.  In summary this research indicates:

  1. Swimmers go deeper in deeper water
  2. Older swimmers go deeper than younger swimmers
  3. All ages ( and experience levels) of swimmers go shallower when asked to do so
  4. There are differences in head depth as a function of block height
  5. Virtually all starts are fast enough to cause injury if an impact should occur
  6. Very few swimmers go deeper than five feet even in seven feet of water. 

We are at a crossroads between safety versus programming when they should be compatible.  The key to safety in this matter is instruction and how participates learn how to dive.  The reality is no water depth is safe without proper instruction.  When making an informed decision, one must balance the threats and benefits from an activity.  There has been plenty of research on the health advantages of recreation, lesson, fitness, and competitive swimming and how it impacts safety and lifestyle. Here’s a nice shout out to water safety programs and ongoing swim lessons nationwide. Even though more and more people are exposed to a growing number of swimming pools at new aquatic facilities across the nation, drowning death rates in the United States have declined in the last decade according to the Centers for Disease Control and Prevention.  

 

Should We Build All-Deep Water Pools?

Is the answer that we build all-deep water pools? And if so, how deep? Twenty years ago swimmers swam nearly their entire race at the surface. Today most elite swimmers swim a large percentage of their races 3 to 4 feet below the surface, utilizing a butterfly (dolphin) kicking technique.  

Championship pool depth may impede many instructional, fitness, and recreational opportunities and consequently, revenue potential. And since people frequent pools for a variety of reasons—fitness, relaxation, instruction, competition, and therapy—today’s swimming facilities do not just accommodate competitive swimmers but are multidimensional centers encompassing all types of swimmers.  

To provide a fiscally sustainable facility, multiple users must be able to use the same space for different purposes at different times. Building an all deep-water competitive pool would significantly limit other uses such as recreation, lesson, fitness and therapy.  The following shows preferred water depths for various types of swimmers. 

0 – 3.5 Feet

        Toddlers

        Recreation

        Wellness / Therapy 

3.5 – 5 Feet

        Recreation

        Lap Swimming

        Wellness / Therapy 

5 – 10 Feet

        Competitive Swimming

        Water Polo

        Synchronized Swimming 

11.5 Feet +

        Diving

Unintended Consequences

Some may suggest that the Facility Design and Construction Module is limited to new construction and would not apply to existing facilities.  I would suggest that given the United States legal system this is naive.  I cannot envision an outcome that defines separate solutions water depth solutions for new and older pools.  In 2001 when the NFSH changed the minimum depth standard from 3 feet six inches to 4 feet, many high school pools moved the starting blocks from the shallow end of the pool to the deep end.  For pools without diving wells, this proposed change would likely require structural modifications to the pool shell.  To renovate a six lane 25 yard pool from a maximum water depth of 4 feet to 6 feet 7 inches for a distance of 20 feet in front of the pool edge is estimated to be in the $200,000 range.  Not only will the pool depth be effected but the mechanical equipment will need to be upgraded to services the increased water volume.  For new construction the differential cost is not as great with an estimated increased cost in the $20,000 range.  

Conclusion

The State of Michigan is the only state that requires water depths under starting blocks to be 6 feet 7 inches.  If the MAHC codifies this unique standard it will change the national standard as defined by the governing bodies of sport.  In this writer’s opinion, the unintended consequences maybe the dramatic decline of competitive swimming activities in the United States similar to the effects of removing high dives across the country in the 1980’s and 1990’s.  If this happens what are the negative health effects on childhood obesity and an increased sedentary lifestyle?