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Chena Fresh Gardens


Chena Hot Springs Resort is working toward becoming a self-sustaining community, and an important part of making this vision a reality is to strive for greater independence in food production. The Chena Fresh Gardens program began in 2004 with the installation of a small test greenhouse, which has since operated year round and is heated entirely with water from our geothermal resource. One January, we were able to maintain the standard greenhouse temperature of 78°F while outside temperatures dropped to -56°F, which is typical for Interior Alaskan winters. This 134°F temperature differential was the largest recorded for any controlled environment production facility in the U.S.

In the last 4-6 years Chena Fresh Gardens has added to its original growing facilities with the construction of a new 4320 ft2 greenhouse, a 2000 ft2 high tunnel and a quarter of an acre of outdoor garden beds to provide our restaurant with a greater variety of fresh produce on a year round basis. Crops grown by Chena Fresh Gardens include tomatoes, lettuce, green beans, sweet and hot peppers, cucumbers, zucchini, potatoes and numerous other greens and herbs. The purpose of Chena Fresh Gardens is to strive to be an example throughout the state of Alaska for using geothermal and other waste heat systems to become more sustainable.

Chena Fresh Gardens also uses space in the greenhouses each year to produce around 100,000 flowers which are used to fill hanging baskets, unique flower planters and several large flower gardens throughout the resort in order to enhance the beauty of the hot springs during the summer months. 

Using Geothermal Water to Create Controlled Growing Environments in Extreme Conditions


Chena Fresh Gardens erected its first greenhouse, a converted hoop house located next to the outdoor Rock Lake in the summer of 2004. This 1000 ft2 structure was a test installation to determine if growing conditions could be maintained year round utilizing the geothermal resources here at Chena Hot Springs. During the winter of 2005, we experienced outside temperatures as low as -56°F. At the same time, we were able to maintain an interior greenhouse temperature of 78°F.

The hoop house is divided into two areas; an 800ft2 grow area and a 200ft2 air-mixing area. A 2" radiant fin tube is used around the perimeter of the grow area as well as a geothermal air exchanger in the front room to keep the greenhouse warm. 165°F water is pumped from one of the geothermal production wells through the air exchanger where a fan actively blows air across the hot pipes and distributes warm air into the greenhouse.  After passing through the exchanger, the water is circulated through the fin tubes and radiates heat around the baseboards of the house. A small amount of this geothermal water is then deviated through a circuit of piping through an insulated pipe along with a cold water line and back into the original geothermal line; this effectively keeps the cold water for irrigation thawed out all winter long. The water from both heat sources is then returned into the outdoor Rock Lake. The greenhouse is covered with two layers of 6 mil poly-film.  Two blower fans inside the greenhouse work to fill the space between the two layers of plastic creating an air layer of insulation. An arctic entry is also used to prevent large amounts of heat loss or too much cold air from entering at once.  This greenhouse is still in use today and is affectionately referred to by the Chena Fresh Gardens team as "The OG" short for The Original Greenhouse.

A 100' x 20' high tunnel is also operated from early April until mid October. Plants are grown directly in the ground of this grow space.  To extend our growing season with this house, geothermal pipes have been run about 5 inches below the soil and heat the ground all throughout the high tunnel.  Special fin tube radiant heaters are also equipped throughout.  The high tunnel is generally used to produce a rotation of vegetable crops.

In our newest greenhouse, the concept of the hoop house was taken one step further once we had demonstrated successful results in the OG. Two modified Poly-Tex, XA-300, gutter-connected greenhouses, with a total area of 4,320 ft2, were erected on a radiant heated concrete slab. A second building phase added a 28' extension to each of the gutter-connected rooms and a headhouse/storage area for a total square footage of 6500 ft2. The entire greenhouse is modified to have heavily insulated sidewalls rather than the standard roll up poly-film sides. The same 165°F water is pumped through the concrete slab. Each room is equipped with 1-2 geothermal heat exchangers.  Each 30' x 72' room has its own environmental controller and is maintained at different temperatures while the two 30' x 28' rooms operate as an air-mixing area to buffer against the cold temperatures of Interior Alaska. This greenhouse is simply called the Main Greenhouse as it is the largest and produces the most on a year-round basis. 

One room is used for growing hydroponic tomatoes 9 months out of the year. In this room there are approximately 360 indeterminate tomato plants consisting of anywhere from 3-5 different varieties. These tomatoes are grown using a Dutch bucket system. Possibly one of the most unique things about this room however is the substrate that is used. In 2016, the owner of the resort, Bernie Karl, decided to try growing tomatoes in a substrate made up of crushed biochar and crushed, recycled glass. The first year growing with this media was able to produce 9,333 lbs of tomatoes.   

The other room is used for growing hydroponic lettuce and herbs using a NFT (Nutrient Film Technique) bench system. This bench system is capable of growing approximately 2,000 head of lettuce and various herbs on a rotating schedule, Producing anywhere from 24-72 head of lettuce and around 3/4 lb of various herbs per day, 365 days a year. The NFT system is a type of recirculating hydroponic system where a pump pulls from a large reservoir delivers water to each plant and then drains back to the reservoir.  The reservoir is monitored and maintained at a desirable pH and nutrient level. This type of system uses minimal amounts of water. We generally grow around 10 different varieties of lettuce and around 5 different types of herbs in this system.  

Both rooms in the Main Greenhouse are equipped with LED supplemental lighting. Tours are offered twice a day which allow the public to enter the front two rooms of the Main Greenhouse and view the lettuce and tomato production rooms.

Plans for the future:

The Chena Fresh Gardens team is planning a renovation of the high tunnel to include raised beds and a small propagation area to offer us an even earlier start to a growing season. 

Plans are also currently being worked out to convert our 1/4 acre of vegetable gardens into permanent raised beds with removable cold frames and geothermal heating. 

Currently, only the Main Greenhouse is open to tours from the public, but the Chena Fresh Gardens team is working to beautify and upgrade all grow spaces with thoughts of offering a full growing facilities tour in the future.