Category Archives: Design

Which Project Delivery Method is Right for You?

One of the major items often misunderstood on a construction project is the delivery method. Traditional project delivery methods include design-bid-build, design-build and Construction Management.

Historically, the design-bid-build process has been the most common project delivery method for large scale commercial projects. Under this delivery method, the owner holds separate contracts between the ddeliveresign professionals and the construction team. This delivery method is most common amongst publicly-funded projects.  The design team (including traditional building architects, landscape architects, MEP engineers, structural engineers and aquatic design professionals) works directly for the owner to develop a set of construction documents. These documents are then used to create a competitive bidding environment between multiple vendors, manufacturers and suppliers.

The teaming circumstances between the design professionals and the installing contractor are different under the design-build scenario. Under this delivery method, the design-build team is led by the building contractor. The design professionals are then contracted through the building contractor, thus providing the owner with a single point of contact for both the project design and construction.

del 2In design-build, the contractor traditionally works with the owner on the development of a Guaranteed Maximum Price (GMP) based upon partially-developed plans. Design-build can, under certain circumstances, provide opportunities to expedite the overall project schedule. The owner should request that GMP drawings be as complete as possible, and participate in the development of the GMP package to minimize surprises with the pool and any support buildings. While initial construction costs can sometimes be reduced through a design-build process, the owner must be wary of cost-cutting measures that can decrease the lifespan of the facility and increase yearly operational cost, both of which are bad for the owner of the facility.

In the Construction Management project delivery method, the owner typically holds separate contracts with the construction manager, the design professional, and in some cases, the installing contractors. Construction management can either be performed “at-risk” or “not-at-risk.” When not-at-risk, the construction management agency (CM) typically becomes the owner’s representative by managing the project from the back end of design through construction.  In this scenario, the CM does not directly hold a contract with any specific contractor. When at-risk, the CM typically commits to a GMP prior to construction and acts as not only the owner’s representative, but somewhat equivalent to a general contractor during construction. If the owner does not possess knowledge or experience in construction projects, the inclusion of a CM in some fashion can benefit the overall process for the entire team.

Once you have chosen your preferred project delivery method, it’s time to think about the process for selecting your design and/or construction professionals. Several tools are available to assist owners when determining the best team to help create the desired facility. These include Letters of Interest, Requests for Qualifications (RFQ), Requests for Proposals (RFP), and the Interview process. These tools can help determine the proper team who will create and manage the project from start to finish.

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Cast-in-Place vs. Shotcrete Concrete Pool Installation

For many, the question commonly arises as to what type of concrete material makes the best watertight vessel: cast-in-place concrete, shotcrete or gunite. While each have their own strengths, one must consider key items such as geographical/site location, soil conditions and most importantly, availability.

There are many locations in the United States where shotcrete and gunite are not produced. Soil conditions can also play an integral role in the decision making. Questionable and/or remediated soils often call for thicker concrete placement due to the needed increase of structural steel (rebar).

The placement method utilized for concrete is to discharge it from a ready-mix truck down a shoot directly into form work or into a hopper equipped with a boom pump. The concrete is then pumped into forms and must be vibrated for compaction. By contrast, the shotcrete process, whether using wet or dry material feed, may only require single side forming or no forming at all by utilizing the earth as the back form in selected areas. This process utilizes a smaller pump with added air pressure via an accompanying compressor. The air is introduced atshotcrete the end of the discharge hose nozzle, creating a high-pressure discharge of the concrete mix. The pressure creates compaction, thereby enhancing design creativity and application flexibility, often resulting in a savings of time or money. The impact velocity of correctly placed shotcrete quickly compacts the material, yielding an “in-place” mix that’s richer in cement and higher in strength than the same mixture prior to placement. With shotcrete, what appears to be a waste of supplies, known as “rebound” or overspray, in reality ends up in thick, high-energy shotcrete as a portion of the mixture ricochets off the receiving area and away from the placement area. The loss through rebound will vary based on various factors including the dryness of the mix, the shooting distance from the surface area and wind conditions. The expected thickness is generally overshot, trimmed back to the design thickness reflected through “look-outs,” and finished to the required surface consistency and appearance. This process commonly requires more labor for multiple finishers to cut and finish the concrete and laborers to follow with clean-up and rebound removal. Compared to the additional materials and labor required to form both sides for the cast-in-place process, this can often times offset each other. However, cast-in-place does require additional labor for front and back form removal.

Characteristics of how concrete or shotcrete is delivered for pumping or placements are very similar. Typically, regardless of the concrete type, shotcrete or cast-in-place concrete has a 90-minute window from the time it is batched at the plant until it placed. Temperature of the material, air temperature and humidity levels can increase or decrease the set times of the concrete. Typically, ready-mix companies hold back 10-15 gallons of water in the mix so the contractor can adjust the slump of the concrete onsite. A concrete truck typically hauls 8 to 10 yards of concrete and 1 cubic yard of concrete typically contains 38 to 40 gallons of water. Project specifications dictate the required mix design and testing agencies commonly verify the concrete slump of the first truck prior to pumping, as well as periodically through the day. Adding 1 gallon of water over the design mix (amount of gallons of water per yard of concrete) can decrease the strength of the concrete by 200 PSI.

Often overlooked, the curing process is an integral step for optimum intended performance of concrete or shotcrete. The mix design can be perfect and the placement can be of the highest quality, but if not cured properly, adverse effects can impact the quality dramatically. While there are many methods, curing concrete or shotcrete surfaces with water is by far the best method for maintaining adequate moisture and controlling shrinkage cracks during the hydration process. After some time, the concrete starts the chemical reaction that eventually hardens the concrete. Curing vertical and horizontal surfaces with water can be easily accomplished with alternative curing methods considered due to project scheduling, the availability of fresh water and the ability to discharge the water being used. Curing compounds may also be applied to the concrete or shotcrete mix or to concrete surfaces after placement. However, these compounds can also have an adverse effect on the finish materials such as paint, plaster or tile mortar. It is suggested to consult with the finish contractor and the structural engineer prior to concrete placement to verify acceptance of curing compounds.

In closing, the question of which process is better? Well, as you can see, there are many variables to consider. While cast-in-place is better-controlled and suited for close tolerance work, it can be a less economical option. Shotcrete, if applied properly, can also provide a superior watertight vessel. Counsilman-Hunsaker’s advice? Make sure your concrete or shotcrete contractor is qualified to perform their work. Do your research. Ask for references and verify if their nozzleman is American Shotcrete Association-certified. Water test your pool prior to the placement of pool finishes. This process is detailed in American Concrete Institute 350.

Remember that pool finishes, such as paint, plaster and/or tile, are not designed to waterproof your pool. If the structure behind your finish is not watertight, your finishes will only serve as a temporary barrier.

What Makes a Pool Fast?

There are seven basic factors specific to pool design and operation that maximize the performance of swimmers and make pools fast. While they don’t exist in any order of priority, some are more essential than others.

Indoor Air Quality

Most people are familiar with the “swimming pool smell” encountered when walking into some indoor pool environments. That strong smell can even be picked up at an entry lobby before even setting eyes on the pool. The smell is actually chloramines off-gassed from the swimming pool. They tend to reside close to the water surface, which is unfortunate for swimmers, as this coincides with the breathing zone. Highly-competitive aquatic athletes are familiar with pushing their bodies aerobically and anaerobically. In either state, heavy respiration of chloramine-laden air inhibits performance. The good news: there are several ways to dramatically improve overall indoor air quality, and in turn, maximize swimmers’ performances. One involves using proper air distribution over the surface of the water. Another option is to remove chloramines at their point of formation. Medium-pressure UV systems can be installed to help maintain chloramine levels to 0.2 parts per million or less. These systems destroy chloramines during the recirculation process. With improved overall indoor air quality, swimmers’ performances and health are improved as well.

Water Clarity

Pool water must be clear so swimmers are able to see underwater. Clearly, being able to see markings and wall targets allows for swimmers to time their strokes into their turns and finishes, as well as break out from their underwater kicks. Water clarity largely comes down to maintaining ideal water chemistry and water filtration. Newer regenerative media filters on the market in the last 10-12 years in the United States are gaining popularity for projects pursuing sustainability. These filters consume considerably less water than traditional high-rate sand filters. However, they also filter down to 1-5 microns, while sand filters often only capture particulate down to the 25-50 micron range. Ideally, the water must have a turbidity level that does not exceed 0.5, measured with a nephelometer.

Temperature

It’s important for swimmers to be comfortable in the water, which means that water temperature should be approximately 78 degrees Fahrenheit. At this temperature, swimmers’ bodies will not overheat at maximum effort and stress. At temperatures much below this level, swimmers usually complain of stiffening muscles. Additionally, the body will be burning more calories to offset the colder skin temperature. At water temperatures much above 80 degrees, swimmers usually feel sluggish and experience an undesirable rise in body temperature during maximum effort. Something else for designers to consider are the hundreds, if not thousands, of spectators watching the competitive swimming event. These guests and their body height can cause slight differences in the rate of evaporation, and contribute to temperature conditions within the pool space.

Visibility

Good underwater visibility is the product of exceptional water clarity and light level above the swimming pool. For the highest level competition pools, some regulatory bodies require 100-150 foot candles of lighting over the water surface so that visibility for swimmers, as well as for the remote viewing audience, is satisfactory. This often requires direct illumination from above utilizing fixtures located directly over the water surface. With the overhead light source directed perpendicular to the water surface, light will penetrate the water medium and reflect off the white pool interior. Underwater lights increase the light level under the water surface not only as a source, but also as an enhancer to the reflected light. In this manner, it creates an ideally-illuminated environment for competitions.

Subsurface Turbulence

Subsurface turbulence can inhibit the forward motion of swimmers. This turbulence can be caused by water currents from the pool’s recirculation system, but this varies upon the type and location of the inlets. Circulation flow currents can be a problem if they exist in the bounded water volume of the race course. Of greater concern is the presence of rebound turbulence created by swimmers. This is more prevalent during starts and turns while executing underwater dolphin kicks. The turbulence reaches the floor of the pool, rebounds and returns to the surface in such a way that it interferes with the forward progress of the swimmers.

Surface Turbulence

Swimmers have long been aware of the difficulty of swimming through rough water as compared to a smooth, flat surface. It’s this basic understanding that led to the development of floating lane line dividers, and subsequently to the wave-quelling designs used today. Floating lane lines absorb and contain wave energy created by swimmers within each lane. The primary benefit of contemporary lane lines is to isolate the turbulence in one lane, and impede it from crossing into adjacent lanes.

We also tend to see the dissipation of surface turbulence inside the lane where swimmers have created agitation. Essentially, when swimmers swim down the lane, they create surface turbulence that impacts their speed when returning through the original point of dissipation. As a result, the swimmer experiences greater impedance at the first third of each length, with the exception of the first length. Conversely, the least impedance occurs in the last third of each length when the surface has experienced the longest period of time from the last surface agitation.

Psychological Influence

Psychological impact is a subjective variable that positively or negatively influences all athletes at the start of a race. While the mental attitude of swimmers cannot be influenced directly, there are several things designers can do to heighten the excitement and adrenaline levels of the athletes.

Design architects should educate themselves about the procedural experience of competitors. There are identifiable psychological impact points from arrival at the facility, to locker room preparation, to warm-up routines. Energy builds up as more and more athletes arrive, and as the start time draws nearer, there are behavior patterns each competitor carries out. Typically, we see competitors isolate themselves, meditate and concentrate on the task ahead of them. Privacy may be an empty room, a corner under the stands or simply a towel over the head. For high-end competitions, a ready room is provided. The location, design and appearance of this room can be a huge motivating factor for swimmers.

Conclusion

If all of these environmental conditions come together just right, your facility will understandably be known as a “fast pool.” Swimmers will be capable of reaching their full potential, and you’ll see more personal best and record-breaking times at your facility.

What is the Best Finish for My Pool?

In today’s market, pool owners have the ability to choose from a multitude of different pool finishes. From paint options that are more cost effective, to customizable ceramic tile options, each style has its associated benefits and drawbacks. While the decision process can be exciting, the array of different finish options can make it a daunting task. Let’s dive into the specifics of the most common pool finishes on the market, and hopefully take some of the stress out of your decision-making process.

Epoxy Paint

Epoxy paint is the most cost-effective option for pool finishes. While not recommended for indoor pools, it is an efficient option when considering design parameters for outdoor leisure pools. For instance, epoxy paint is great for pools constructed in climates that have to be winterized, or pools that will be left empty during the winter months. Unlike most plasters, painted pools are unaffected when exposed to the winter elements.

The expected life cycle of an epoxy-painted pool finish is approximately one to three years, as the epoxy paint will fade with time. Re-coat frequency is often an owner-driven appearance issue, rather than a coating failure issue. An epoxy finish can be re-coated with the same type of coating as the original finish with a minimal amount of surface preparation.

Lighter colors such as white or light blue are preferred. Darker colors (royal blue, dark blue, black, etc.) are not recommended for the entire pool surface as they tend to prematurely fade due to water chemistry and UV rays.

Plaster

Plaster is the oldest and the most common pool finish on the market. Plaster/marcite is a combination of cement, sand, calcium carbonate (plaster dust) and water. When applied, it is troweled until the “cream” is brought to the surface. The cream hardens and becomes a protective layer about as thick as two to three sheets of paper. Because it has such a thin application, acid washes can damage it pretty easily.

Plaster is typically the preferred finish for indoor pools. It has a longer life cycle than epoxy paint, but doesn’t have the longevity or aesthetic appeal of tile. Plaster is traditionally white, but colored plaster is available as well.

Based on Counsilman-Hunsaker’s experience, plaster will spall, or flake off, anywhere from 5-15 years (5-7 in high traffic areas) from installation. And unfortunately, there is no reliable fix. Plaster spalls due to problems with the original bond to the concrete wall, or due to aggressive pool water leaching mineral from the coating and weakening the plaster.

Aggregate Plaster

Aggregate plaster is essentially the new generation of a traditional plaster finish. It is made up of plaster combined with different types of aggregate like granite, quartz, marble, other stone/pebbles or glass beads. The added aggregate protects the plaster and provides texture and color.

The most common types of aggregate finishes are Diamond Brite, Pebble Tec and Pebble Sheen. Most aggregate finishes need to remain hydrated at all times (even during winter months) in order to prevent shrinkage cracking.

The lifespan of aggregate finishes is generally longer than that of plaster. Compared to traditional plaster, aggregate finishes are more resistant to chemicals and staining. Our experience has shown that aggregate finishes, if maintained in a wet or moist condition, will typically have a lifespan of 7-15 years. In most cases, you can expect to achieve a 10-year life.

The cost of aggregate finishes has a slight premium of approximately $2 per square foot when compared to traditional plaster. However, when looking at life cycle cost, the increased lifespan of aggregate plaster generally proves to be the better long-term economic decision.

Ceramic Tile

Ceramic tile provides a durable and attractive finish for indoor swimming pools. Its use for exterior pools, however, may not be cost-effective or appropriate considering the environmental conditions to which the finish may be subjected. For interior competitive venues, ceramic tile remains the recommended finish.

Tile can be completely customized for a look that is unique to your pool. Tile comes in a variety of styles, shapes, colors and textures. Through tile patterns and designs, you can tailor the look of the pool to your liking. Although it is the most expensive and labor-intensive pool finish to install, it has the longest lifespan. If tile is properly maintained, it can last 25-50 years. The grout will need to be touched up from time-to-time, but generally speaking, little maintenance is required.

On outdoor pools in particular, “frost-proof” tile is recommended. In order for tile to be considered “frost-proof,” it must be porcelain in construction. Glazed ceramic tile should be avoided on all outdoor pools in a freeze/thaw climate, and only considered on a case-by-case basis.

What are common concerns and options for winterizing a commercial swimming pool?

Winterizing a seasonal outdoor pool can vary greatly depending upon location, pool type, groundwater conditions, local sewer capacities and a host of other factors. If an outdoor swimming pool is not properly winterized, catastrophic damage to below grade piping, heaving and floating of the pool tank, undue wear on pool mechanical equipment, delamination of finishes and numerous other physical and cosmetic issues will can occur.  And when winterization is required, there are traditionally three (3) options for consideration regarding whether or not water is remains within the pool tank.  These options include leaving the pool water at or near the normal operating level, a partial draining of the pool, or a complete removal of all pool water.  Regardless of the method that is used there are several considerations that should not be overlooked.

Heights Recreation CenterIn almost all geographic regions there are will be variations in outside air temperature and seasonal precipitation that will result in varying hydraulic forces from both the surface (water within the pool basis) as well as potential upward forces from fluctuations in groundwater levels. In climates that experience extended periods of time where the temperature remains below freezing, these problems are complicated by the freeze-thaw cycle.  Water trapped in porous areas of concrete or behind ceramic tile or leaking through improperly caulked expansion joints may cause damage at the first hard freeze.  Frost heave describes the lifting or displacing force of freezing water.  If the pool is to be drained and left empty, the surrounding soil must be well drained and dry.  Even amounts of water too small to cause hydrostatic damage can cause frost heave, and this lifting or movement can crack concrete slabs or displace sections of the pool structure or deck.

High Groundwater Table Considerations:

In situations where the level of groundwater is high, the force exerted on the pool bottom and sidewalls can result in cracking, differential movement or other structural damages. In the most severe conditions where groundwater level are noticeably above the pool bottom, portions of the structure can be lifted or moved by the buoyant forces.  If circumstances require the pool to be drained, the groundwater level should first be determined, and confirmation that hydrostatic relief valves are present and functional should be completed.  Hydrostatic relief valves allow groundwater to flow into the empty pool when the surrounding water table is too high thus providing a ballast to the upward buoyant pressure.   This valve functions as a check to prevent the flow of water from the pool into the ground when the pool is full.

Swimming pools located in areas with high water tables often have systems of perforated pipes or under-drains that allow water to flow away from the pool. These systems either carry the water into porous soil areas adjacent to the pool or allow drainage by gravity.  For the gravity method to succeed, considerable changes in ground level must be present, as the pipe must go to “daylight” at an elevation several feet below the bottom of the pool.  In some instances, these drainage networks connect to a sump or pit where the groundwater level can be observed and removed via a sump pump.

Pool Draining:

For emptying the pool, a quick and efficient means provided via gravity is almost always preferred.  If gravity is not possible, a filter bypass line can be designed on the discharge side of the recirculation pump and piped to the backwash pit.  A 3” or 4” line will typically be used with a normally closed butterfly valve located on the drain line.  The difference in the recirculation rate and what the sewer can handle can be sent back to the pool through the filters.  A small feature pump could also double as a drain down pump. The pump would need to pull from the deep main drain and the project engineer should confirm the pump size with the sewer capacity.

The filter recirculating pump may not be able to pump the pool completely empty because of capacity discrepancies between the pump and the sewer, as well as vortexing concerns at the main drain outlets. For this reason, occasionally a small low head pump is provided for drawing the final water out of the pool.  The suction for this pump is located at the bottom of the deepest main outlet sump.

frozen-poolsLastly when winterization protocol requires the pool tank to have water remain, the best and most appropriate off-season protection for both pool and people is a safety cover. Such a cover protects the pool from debris, greatly reduces the growth of algae, and protects children and animals from falling in the pool.

There are four rationales for leaving water in a pool in the off season:

  1. It is a way to winterize the floor inlet system.
  2. It will stabilize the pool shell should the ground water table rise during the spring and hydrostat malfunctions.
  3. It protects the pool floor surface from spalling due to sudden changes in temperature over numerous seasons.
  4. It insulates the pool floor and thus the substrate and the soil beneath. If the soil freezes, the floor can heave creating cracks and possible loss of water.

Winterization Items beyond the Pool Tank:

Thoroughly cleaning and lubricating, coating or protecting virtually everything in the swimming pool vicinity can help stave off corrosion during the off-season. Equipment must be adequately winterized, dismantled, or removed and stored.  Chemicals must be properly removed – not simply left sitting for the next season, dumped into the pool or poured down the drain.

If the pumps, hair and lint pot, filter, and heater are not drained, they can freeze, crack and have to be replaced. Likewise, chemical feeders may be damaged.  In extreme cold weather climates providing temperament heat within the pool filter building is a good recommendation.

An outdoor pool in a freezing climate must have all water removed from its pipes before a hard freeze occurs.   Therefore, blow out all pipes by means of an air blower and a winterization tap, and then cap all pipes.  For added protection against freezing pipes, the pipes can be filled with antifreeze.  A ½” hole should be tapped in the piping after the check valve on pressure piping and plugged, or a 1” pipe with a ball valve can run to the nearest pump pit drain.  Either option should allow the pipe to be drained.  All of the piping needs to drain to the deep main drain to help eliminate low spots and freezing.

Hidden Concerns:

A pool cannot winterize itself like a self-cleaning oven or an auto defrost freezer. Therefore, thorough detail must be followed during your winterization process.  For instances where the pool is to be completely drained, all too common a complete and sufficient draining and subsequent blowing air through the pipes is not completed.  Water trapped in a 45 or 90 degree fitting will break first as compared to straight pipe because the ice is constructed when it begins to expand.  As compared to a vertical or horizontal run of pipe water will freeze and expand without breaking the pipe.

If water is left in the pool, ice can damage the water-line tile, or worse yet, the gutter tile. Ice can also damage the underwater lights if the water level reaches the level of the lights due to evaporation, a leak at a light niche or due to unusual rain.  A winterizing option is to remove the light from the wet niche, place it in a plastic bag with a brick and sink the light to the bottom of the pool, which will keep the fixture gasket wet and avoid drying it out which will result in the gasket leaking at the start of the season.

Waterslides and recreational water features will constantly expand and contract with extreme variations in temperature. Joints between slide flume sections will need to be caulked as thermal expansion and contraction leads to leaking slide joints.

Lasting Recommendations:

The pool should be engineered so the operator can winterize the pools easily and thoroughly. Design the piping system so water will drain by gravity to daylight, i.e. filter room, surge pit or nearby manhole is ideal.  All of these sites will have dedicated drain pipes with on/off valves.  If draining to daylight is not possible, provide galvanized female threaded fittings on the pressure and suction lines in the filter room for convenient use with a compressor.  With the compressor, blow the respective lines with propylene glycol antifreeze.  The antifreeze will mix with any residual water in the lines and thereby lower the freeze point of the mixed liquid in any undulation in the underground piping.

If the pool must be empty for the winter, drain the pool, winterize all of the lines with a compressor and antifreeze, and pump the main outlet pipes dry with a sump pump in the outlet sumps. Once the pool piping has been drained plug all lines with expandable rubber plugs.  Plug all inlets and pipe openings in skimmers.  Always remember to confirm that all hydrostatic valves are operable.

If the owner permits the pool to be half full of water during the winter, then the floor inlet piping will not need to be winterized. The water depth will preclude freezing to shallow end floor and thus below pool lines will be protected.   However it is possible that if some water is left in the pool, the water level may change over the course of a winter via evaporation or precipitation causing unforeseen issues.  Therefore, a consistent protocol for monitoring the pool must be done.

Overall, winterization of the seasonal commercial pool should not be considered a daunting task. As long as a consistent process is in place resulting in a complete and thorough winterization, your outdoor pool should have the ability to withstand even the harshest of winter conditions.  However, without a good winterization process, your pool may experience premature aging and unforeseen repairs.