Evaporation from the wave pool and spa areas of the water park, combined with people gain, created the demand for incoming air to absorb 944 lbs/hr of water to maintain proper conditions.

Once it was determined that condensation was not a concern, the next step was to figure out exactly how much moisture would be generated internally and need to be removed. To calculate the amount of water that would evaporate due to the various pools and people, the following equation was used:

(Equation 3) wp = 0.1A x (pw – pa) x Fa

Where:
wp = Evaporated moisture (lb/hr)
A = Area, (sq ft)
pw = Saturation pressure, evaporated water vapor, (in. of mercury)
pa = Partial pressure, water vapor, in ambient air, (in. of mercury)
Fa = Activity factor, (from ASHRAE 1999 Table)

In the case of the Alaska water park, the following data was used: Saturated vapor pressure, spa: ps = 2.11661 in. Hg. at 103°; saturated vapor pressure, wave pool: ps = 2.17608 in. Hg. at 84°; saturated vapor pressure, air: pa = 1.25388 08 in. Hg. at 86°; room air dewpoint = 74.5°, Þ ps =0.855

Then for each of the components, the contributed moisture was calculated as follows:

Vapor produced by the spa:

wp = 0.1 x 354 x (2.11661-0.855) x 1.0 = 44.66 lb/hr

Vapor produced by the wave pools:

wp = 0.1 x 15,335 sq ft x (1.17608 – 0.855) x 1.5 = 738.6 lb/hr

People Gain

wp = 0.325 lb/hr x person x 200 occupants = 65 lb/hr

Total vapor produced = 44.66 + 738.6 + 65 = 944 lbs/hr

This means that the incoming air must be capable of absorbing 944 lbs/hr water, without exceeding the 86°, 60% rh indoor conditions recommended by ASHRAE1.

Having defined the amount of moisture that needed to be removed from the atmosphere, the next step was to define the method of calculating just how much air would be required to accomplish this.

From the psychrometric chart:

Indoor moisture content at 86°, 60% rh = 0.016 lb/lb of air

Outdoor moisture content at 71°, 60° wb = 0.086 lb/lb of air

The available humidity pick-up between outside ambient conditions in the summer and indoor ambient conditions is the difference between these two values = 0.0074 lb/lb of air.

Density of air at standard temperature and pressure = 13.5 cu ft/lb

D moisture = 0.0074-13.5 = 0.000548 lb/cu ft of air

In order to calculate the quantity of air necessary to absorb 944 lb/hr of moisture, the following calculation was performed:

(Equation 4) cfm = 944 lbs/hr/0.000548 lb/cu ft/ 60 min/hr = 28,710 cfm

As this calculation was performed using data from the peak design condition for summer, (when incoming air would be at peak humidity, and therefore have the least absorption capability), the 28,710 cfm represents the maximum outside air needed for dehumidification. It should be noted that in the winter, a mere 14,000 cfm of outside air is adequate for fully dehumidifying the space; there is very little water vapor in the air at temperatures below ing.

. Another special concern was avoiding stratification of heat and humidity inside the 50-ft tall structure. To keep the hot air flowing throughout, the engineering solution was to supply most of the air via a below-floor plenum (Figure 1). As this was already excavated volume, with one wall being the foundation itself and the other the vertical side of the lazy river, using it as a plenum was a creative idea, which did not add any construction costs. This use of an underground concrete supply air plenum gave the water park a clean, uncluttered look, delivering hot air that migrates up to the return air grilles mounted high at the roof peak.

In essence, the airflow creates a very efficient delivery pattern, one that minimizes stratification and reduces pockets of humidity in the space. Any water that splashes from the floor grilles is collected in sumps and pumped out to avoid standing puddles, which could create a health hazard.

One constant feature to be found at any great water park is the “lazy river.” H2Oasis has its own lazy river called the Never Ending River. The water stream flows at 5 miles per hour, in a channel 575-ft long, along the perimeter of the 40,500-sq-ft building. H2Oasis uses the Never Ending River to promote fitness and fun together, by offering a program called Riverwalk. The program allows guests to exercise against the current of the Never Ending River. More than 200,000 gal of water are filtered for the Never Ending River everyday.

Elsewhere, the water park’s wave pool reaches a depth of 6 ft, sloping to 1 ft at the shallow end. This feature can generate up to 4-ft waves. The shallow part of the pool has a “mushroom” water drop; the mushroom rains down water from its brim.

Another special feature of H2Oasis is the children’s lagoon. What makes this lagoon unique is the Sea Dragon Pirate Ship. This pirate ship consists of six water cannons, four on the ship and two on the “beach.” The pirate ship extends 40-ft in length, inside a 12-in. deep pool. There are seven slides on the pirate ship for children to play on. About 400 gpm of water race through the ship.

After years of planning and construction, Alaska has its very own water park. Many people were skeptical of the idea that a water park could be sustained, let alone the technical challenges of building one. Numerous people inside and outside the state of Alaska pulled together to build one of the most unique water parks in the world, making H2Oasis the fifth largest indoor water park in the United States.