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How to build a fiberglass pool in Door County WI

Updated: Dec 30, 2020

Door County, WI is arguably one of the most beautiful counties in all of America. However, behind all that beauty, mother nature is hiding a huge surprise for potential pool owners. This is where hiring an experienced fiberglass pool builder is critical to your project's success and staying on budget.

For those not familiar with the Door County region they may be surprised by the fact that bedrock lies just a shovel's depth under the soil in many areas of Door County. At Pool Pros we are well aware of this natural anomaly and have a specific process to build pools in these conditions. When you are researching your potential pool builder, be sure to check out their process of building pools within the bedrock.

Due to its unique topography and geologic features, Door county has very shallow bedrock depths that require a unique process to build a fiberglass pool. The Door County Peninsula is part of what is known as the Niagara Escarpment that ranges from Chicago Illinois all the way to Niagara Falls on the Canada and U.S. border.

The Niagara Falls
Niagara Falls
The Niagara Escarpment
The Niagara Escarpment

THE NIAGARA ESCARPMENT is a long escarpment, or cuesta, in the United States and Canada that runs predominantly east-west from New York through Ontario, Michigan, Wisconsin, and Illinois. The escarpment is most famous as the cliff over which the Niagara River plunges at Niagara Falls, for which it is named.

The Escarpment is a UNESCO World Biosphere Reserve. It has the oldest forest ecosystem and trees in eastern North America.[1]

The Escarpment is composed of an outcrop belt of the Lockport Formation of Silurian age and is similar to the Onondaga Formation, which runs in a parallel outcrop belt just to the south, through western New York and southern Ontario. The Escarpment is the most prominent of several escarpments formed in the bedrock of the Great Lakes Basin. From its easternmost point near Watertown, New York,[2] the escarpment shapes in part the individual basins and landforms of Lake Ontario, Lake Huron, and Lake Michigan.

Karst Topography in Door County WI
Door County Karst Topography

KARST TOPOGRAPHY is a defining feature of the landscape of the Door Peninsula. In this area, the combination of shallow, gravelly soils above porous limestone means that water moves very quickly through the landscape and the bedrock is very shallow.

Karst is a landscape with surface and underground features like caves, sinkholes, disappearing streams, and subsurface drainage. These features result when the bedrock (often limestone and dolomite) is easily dissolved by water. When the rock is dissolved, cracks and solution channels in the rock can form an underground drainage network. These cracks and channels can rapidly transport surface water and pollutants to groundwater. In karst areas, groundwater can move as much as 100 feet or more per day, while in other areas, groundwater typically moves less than one foot per day. Eventually, this groundwater resurfaces at a spring, wetland, river or lake.


I know, by now you may be asking why should I care about the escarpment or karst if I want to build a pool in The Peninsula of Door County? The answer is budget. The next logical question is why would this affect our budget for our pool project. Well, if your builder is unaware of the shallow bedrock and does not have a plan upfront to deal with the safe and responsible removal of bedrock for your project it will come back to bite you with change orders from your builder that will add thousands to the cost of your project. To address this in more detail we will now break down the proper procedure for building a fiberglass pool in Door County.


These are the steps we recommend prior to agreeing to a contract. These steps will help determine the actual cost and parameters of the potential project. It is best to know this upfront than to be surprised and have to pay more than you were expecting in the end.

STEP 1: The first step of any project is to contact Diggers Hotline to ensure the area you wish to place your pool is free and clear of any underground utilities.

STEP 2: The next step is to contact both your local municipality and county agencies to ensure you are able to build a pool on your property. Shoreline areas, environmentally sensitives areas, and wetlands found on your property may not allow for a pool to be installed. So it is best to make a few phone calls prior to contact a potential builder.

STEP 3: The next step would be to contact a fiberglass pool builder to obtain preliminary pricing for your project. Be sure to let them know your project is located in Door County, WI and that you may have bedrock in your area.

STEP 4: Schedule a time to meet onsite with your potential pool builder to go over the details of your project. In most of Door County bedrock is anywhere from 0-5 ft underground so most pool projects will have to deal with the removal of some bedrock at a minimum. There are 2 options for the removal of this bedrock. One is to use a large excavator with a hydraulic hammer attachment to physically break the bedrock into small pieces to be dug out of the pool dig, or to hire a firm to blast the bedrock. This process involves the use of explosives in the ground to literally blast the bedrock to pieces so it can be excavated from the site. There are pros and cons to both and we will dive into that later in the article.

STEP 5: At this point, it is recommended for you or your fiberglass pool builder to retain the services of a firm that is able to provide detailed Preblast Surveys, Vibrations Analysis, Seismograph Readings, etc. This is very critical because if blasting is required these surveys will aid in the safe and responsible blasting of the bedrock without damaging foundations of buildings, underground utilities and minimize the risk of groundwater contamination. There will be a cost to this but if you skip this step you are risking potential damage to your property and added cost to the project in the long run. There are several contractors in Door County that offer this service.


Now that you have the surveys and analyses completed, your builder should have all the information required to provide you with proper pricing and a game plan for your fiberglass pool build. Now we will dig into the process of installing your Door County Fiberglass Pool.

STEP 1: The first step is for your builder to layout the pool with paint and or string lines. At Pool Pros we use bright pink marking paint as it a color that is not used by any utility marking service so there would be no confusion as to where the pool will be located. We also mark out the areas where the trench will be needed for the underground plumbing from the pool to the pump and filter location.

STEP 2: If blasting is required the next step is for the blasting company to come in and drill holes in the bedrock in strategic locations that are outlined by the surveys provided earlier in the process. After these holes are drilled into the bedrock, explosive charges are placed in these holes and are covered with a small amount of soil to reduce the sound and debris. This is called the pre-shoot method of blasting and is most common. Take a quick look at these 2 videos. The first is from Paschke Blasting of Fish Creek.

STEP 3: Once the blasting equipment is removed from the site, the pool is then excavated down to the solid bedrock. Once all the loose rock has been removed the hole is backfilled with 3/4" clean stone and compacted in lifts until the pool base matches the dig specs from the manufacturer.

From here on out we install your fiberglass pool the same as all of our traditionally installed fiberglass pools using the "River Pools Way" which guarantees the full manufacturer warranty and exceeds industry standards.


The Moral of the story is that to build a fiberglass pool successfully and within your original budget in Door County, WI there are critical steps you as a homeowner must do before your purchase and specific questions you must ask of your potential fiberglass pool builder to ensure a smooth process. If your builder does not have a clear cut process such as our process outlined above, you may want to rethink that arrangement. Pool Pros specializes in and only builds fiberglass pools in N.E. Wisconsin and throughout Door County, WI. For a quote on your Door County, Fiberglass Pool call Pool Pros at 920-770-0107 today.



Green Bay, WI 

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  • This website contains an abundance of information that has been created over the last decade or more. Some of the content on this site may reflect prices, perspectives, processes, entities, and names that were relevant at the time but may not be as relevant today. Consumers should consult a Pool Pros associate for the most accurate and updated information based on the unique conditions of their property. Consumers should verify specifications with the installing Pool Pros rather than relying on the information on this website, which is not intended to be a final specification.

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