Among all the constructed water features found in a golf course development, irrigation reservoirs are the largest. In some cases, they may cover dozens of acres. Typically, they’re used to provide water for the course’s irrigation systems. This water can be used for both the nightly or weekly watering regimen, or as long-term storage in case of an extended dry spell or drought. Ponds may be used to mitigate flooding problems in rainy weather and in some cases, developers can even coordinate with local municipalities to assist with meeting their needs, like receiving and storing local treated effluent. Aside from purely practical uses, lakes can be sited to provide visual appeal, increase the value of waterfront lots, and support diverse wildlife habitats. As the scope of amenities in planned developments expand, lakes large enough to support boating, sport fishing and other recreation may become par for the course.

In nearly all instances, golf course storage ponds are constructed using earthworks dams and embankments. This type of dam has significant cost advantages to other types in the case of most small installations because the excavation of the pond itself provides the bulk of the construction materials. In all cases, dams are designed to safely restrict the natural flow of water and contain it within a specific area. Dams are complex structures and are subject to detailed specifications and regulations put in place by local, county and even state law. It is imperative to engage a qualified engineer to assess every aspect involved in the construction of a proposed dam and to ensure the structure itself will be able to reliably perform the job it was intended for.

The height and width of a dam embankment will depend on the volume of water it is expected to contain, the depth and grading of the reservoir pit, local weather patterns, the quality of soil, and expected drawdown from irrigation activities. It’s also important to allow for the effects of exceptional levels of precipitation since severe weather events can occur. Consider the potential of intense rainfall and stormwater events when planning for spillways and outlets vs. freeboard space, as well as for extended drought periods where the water level falls and allows broad stretches of shoreline to dry up completely. Management of seepage, erosion control, and of course, general safety must also be considered.

During construction, the soil, clay, and other materials in an earthworks embankment and throughout the water retention area are compacted to increase stability, reduce permeability and to minimize ground movement once water is added. Additional tests are conducted to ensure the embankment walls are not vulnerable to collapse in the case of a rapid drawdown and pressure changes. Erosion is a critical concern for earthworks dams, so embankments must be actively protected and maintained. A good coverage of grass like plants with deep interlocking roots can provide excellent erosion control, but since dams are vulnerable to oversaturation, any vegetation introduced must be able to survive without irrigation. Large specimens, like deep rooted trees, should be avoided since their roots can compromise bank stability.

Where anchoring grasses can’t be successfully grown, riprap is an effective structural support, although it’s rarely an appealing look. It isn’t a permanent solution since even riprap will eventually erode and individual stones can be carried downstream. If that side of the dam is visible to the public, it’s important to take steps to improve the appearance. Rootrap may work in this case - the process involves placing riprap wherever it is needed, followed by filling in around the rocks with topsoil. As plants and grasses grow between the rocks, their roots help keep the rocks in place and the combination makes the slope even more stable. Tough geomembranes can also be incorporated to hold the riprap in place before soil is added.

The most basic parts of a dam include the embankment, typically earthfill or rockfill, a spillway, and overflow outlets. The specific details of an earthfill dam design will include specifications based on the type and quality of the local soil as well as fill material, whether sand/gravel or silt/clay. These qualities also will define limits for the dam’s slope and height. Your engineer will be able to calculate these numbers based on local conditions and regulations.

Freeboard is the distance from the crest of the embankment to the maximum allowed water level. In a properly constructed dam, water that reaches maximum level will automatically enter the primary spillway before it encroaches on the freeboard. Freeboard for a small pond should be a minimum of one foot. Larger bodies of water will need a correspondingly larger freeboard. In ongoing maintenance of the dam, it’s important to monitor whether the crest of the embankment is developing low areas. These low areas reduce the freeboard of the dam and substantially increase the risk of overtopping.

A properly sized spillway is required to prevent overtopping in an extreme stormwater event. Overtopping is one of the primary causes of dam failure and happens with devastating speed. Downstream damage from the resulting flash flood can be substantial, even deadly. Primary spillways, such as risers, provide passive control of water levels and can be made of earth, concrete, or conduit. A drop inlet riser is one example:

Emergency spillways must be included as a secondary protection against overtopping. This secondary spillway outlet is placed within the freeboard area but well below the crest of the embankment. The course of water released from an emergency spillway should be built to withstand rapid flow without triggering further erosion problems. This is a case where riprap may be the best option for protecting the watercourse, at least in the first several meters before it widens, and the water slows down. Wetlands are ideal downstream catchment areas for spillways.

Even in areas where there are natural lakes and ponds, it’s necessary to examine the soil in the proposed pond location to determine its suitability to hold water. Seepage is a concern for nearly every constructed water feature on a golf course, since it can result in significant loss of stored water, which means smaller features may require regular topping off to maintain an acceptable appearance. If seepage occurs, saturated soils may become eroded and even lose structural stability. To avoid seepage and minimize water loss, golf course water features are customarily sealed in some fashion. There are several options for sealing or lining, ranging from simple compaction to high tech reinforced geotextiles.  Even large irrigation lakes are lined, especially if the climate tends toward hot and dry with scarce alternative sources of water. 

Clay liners are an all-natural choice for lining large ponds of all types. In cohesive soils with a high percentage of naturally occurring clay, this kind of liner can be effective and relatively inexpensive to install. A seal is achieved by tightly compacting the soil along the bottom and sides of the pond, including the dam itself. A very densely compacted clay will be highly impermeable to water, will resist swelling and contraction and will minimize settling of the underlying soil. To achieve proper compaction, the clay must have an evenly distributed moisture content that produces a stiff clay with good plasticity, not unlike modeling clay. This texture permits easy molding and elimination of seams and air pockets, but moisture is acceptable only within a narrow range. It’s critical to maintain this ideal moisture content and malleable texture through the entire construction process since dry clay will not seal with wet.

Clay liners can be excellent options for lining golf course ponds if conditions are suitable. However, the potential need to truck in large volumes of clay from other sites and then thoroughly mix it with local soil while maintaining the ideal wetness will add to the expense. Clay liners also need to be quite thick - at least 12”, while some professionals recommend 24” as the starting point. Ponds deeper than 10’ require even thicker layers to limit permeability as hydrostatic pressure increases. Finally, both during and after construction, no section of clay can be permitted to dry out, whether during normal drawdowns or prolonged drought. If it does dry, the clay will become brittle and subject to cracking and shattering. Even when exposed to water again, it will not regain its former malleability and will simply erode. To protect against this risk, a continuous protective layer of soil or subsoil of at least 6” is necessary, although more is preferred. This is where clay liners exhibit one of their biggest disadvantages. Even large and deep ponds will lose significant available volume to the combined thickness of the liner and protective soil layer. In a smaller pond, the percentage of lost volume can render it useless.

Sodium bentonite is another popular liner for ponds. It’s a naturally occurring clay with specific properties that make it especially effective for lining ponds. Correctly installed, it can absorb several times its weight in water and expand up to 15 times its original volume, until it has formed an exceptionally dense, watertight seal. Because of its elastic properties, bentonite can handle a small amount of ground movement and can self-heal small cracks or other minor damage. On the downside, bentonite must always be wet. Any shrinkage due to reduced pond levels associated with drought or an intentional drawdown for repairs will result in cracking and crumbling of the liner. Bentonite cannot be installed on steeply sloped sides because over time it will slump down to the pond bottom and leave the sides uncovered. It can also take exceptionally large amounts of bentonite to seal even a small pond, depending on the soil type. According to one vendor’s site, sealing a pond over silty loam requires about 1lb of bentonite per square foot. At 43,560 square feet per acre, a 10-acre pond would require an incredible 200 tons of bentonite. Installation of a bentonite clay liner for this kind of large project would be arduous indeed.

Geosynthetic clay liners (GCLs) are a combination of bentonite clay and synthetic liner that aim to capture the advantages of each while mitigating their respective disadvantages. Sometimes called clay blanket or bentonite mat, the liner consists of some sort of geotextile membrane fabricated to hold small amounts of bentonite clay within stitched or sealed pockets. This design helps keep the bentonite evenly distributed and allows for installation on steeper slopes without an eventual slump. It also makes installation significantly easier. On the downside, GCLs are relatively thin, which makes them more vulnerable to punctures than ordinary clay, especially during installation. They are also susceptible to friction damage where the liner meets other materials, and since much less bentonite is involved, increased hydraulic permeability can become a problem.

Geomembranes are barriers used to control fluid migration. One popular example is polyvinyl chloride (PVC). It’s commonly used for lining anything from backyard fishponds to fish hatcheries to streams. In contrast, geotextiles are permeable, high strength textile sheets made from polymers such as polypropylene and polyethylene. They’re commonly used in applications where strength and durability are paramount, such as protecting and reinforcing weaker geomembranes. For pond liners, combinations of geomembrane and geotextile materials are usually referred to as geotextiles. In combination, fused layers of the two types can provide impressive strength, flexibility, durability, and watertightness.

PVC (polyvinyl chloride) liners are a type of geotextile and are usually the cheapest liner option, but they suffer from a host of disadvantages. While they’re in the middle ground regarding weight and puncture resistance, PVC can include trace amounts of arsenic and other toxins which are lethal to fish. PVC liners are vulnerable to splits and cracks, are not suitable for cold climates, and will quickly degrade when exposed to sunlight. To maintain flexibility, PVC is combined with plasticizers, which are often toxic and can leach into stored water. Plasticizers have been linked to significant pollution and environmental damage.

EPDM (ethylene propylene diene monomer) liners are essentially a synthetic rubber, which makes them soft and very flexible, but they’re the least puncture resistant of the geotextile options and always require underlayment. While EPDM is fish and plant safe, it is also the heaviest liner type, which can make shipping and installation difficult. In addition, the heavy panels must be relatively small to facilitate shipping and installation, so extensive seaming must be done on-site with glue and tape. In a large project, this is a time-consuming process that presents plenty of opportunity for errors.

Reinforced polyethylene liners (RPE) are highly resistant to punctures and tears, are thinner and more flexible than other types, and are lighter and substantially easier to install. Three times stronger than EPDM and ⅓ the weight, RPE is considered the most durable liner available, does not require a protective underlayment, and is both fish and plant safe. RPE liners can last for decades and some types are manufactured with coatings that make them virtually impervious to UV exposure.

For more information on the specs of our RPE products, contact us at btlliners.com. We offer one of the largest selections of specialized, heavy duty, RPE liners in the industry. In fact, BTL co-developed the world’s first double scrim reinforced RPE and we continue to be recognized as an industry leader and innovator in RPE liners.

When planning your water features, whether it’s a relatively simple water hazard or a working irrigation pond, your choice of liner should always be carefully evaluated. Your liner will be subject to a lifetime of wear and tear, including errant animals, hungry herons with sharp claws, and clumsy golfers determined to retrieve their favorite ball. Extreme weather and other unplanned-for situations should always be included in your plans, as should eventual replacement. As in most things that need to last, the cheapest pond liner is rarely the best value.

PVC liners are generally expected to last only about 10 years with normal wear and tear. Over time, plasticizers will erode, which renders the liner increasingly brittle. Cracks or tears will start to appear, and seams will begin to leak. Since the glue used in patching PVC liners can increase brittleness itself, it’s best policy to simply replace the liner at the first sign of age. Of course, in large irrigation ponds or in places where wildlife and fish have taken up residence, that can be a tall order.

Compared to PVC, EPDM liners perform relatively well with exposure to UV, ozone and weathering. EPDM liners even have an expected lifespan of about 20 years if they’re continuously covered well, but since panels must be glued together with tape rather than welded, some amount of leaking over time is inevitable.

With proper selection and care, RPE liners from BTL Liners can last up to decades longer. Our RPE products are reinforced with double scrims and are installed with the industry’s largest panels which require absolute minimum seaming. Since seams are a perennial source of leaks, BTL’s products enjoy an advantage from day one.

Small tears or punctures in PVC liners are common, especially as the liner ages. Repairs can be performed using a patch and special glue, or the liner panel can be completely replaced, which might be the best option since even glue itself can cause increased brittleness. The tape used during installation to join PVC panels together, however, is not a suitable option for repairs. Similarly, patching EPDM requires a two-part epoxy and tape, but it can definitely be a challenge to roll the patch over a firm flat surface to achieve full adhesion when you’re working on the bottom of a drained pond. In contrast, patches for RPE liners are quickly applied using a hot-wedge or hot-air welder, but tape is still an option if a welder is impractical.

Reinforced geomembranes are made with reinforcing scrim tape sandwiched between outer coating layers. This core creates a ripstop function that prevents small tears and holes from growing, thanks to the interlocking strips of tape. This means that reinforced pond liners are far more durable than either PVC (particularly vulnerable to tears) or EPDM (exceptionally prone to punctures).

It’s a fact of life that all ponds will eventually require maintenance to retain both beauty and function. When the time for cleaning, dredging and other maintenance arrives, having a reinforced liner installed from the beginning will minimize tears or damage leading to leaks. The multi-layered construction of RPE helps the material flex instead of tearing, which also happens to reduce strain from freeze and thaw cycles.

PVC liners are vulnerable to both UV and ozone, and a minimum of 12” of covering sediment is recommended to avoid rapid degradation. EPDM is more resistant than PVC, and it is sometimes offered with treatments that offer some defense to occasional exposure, but if exposure is a regular occurrence, EPDM is not a practical option.

RPE liners are more resistant to damage from sunlight than PVC or EPDM from the get-go, but some products have additional coatings that provide exceptional UV protection. While your pond will (hopefully) remain under water most of the time, edges could be regularly exposed during drawdown or even over extended periods of drought. PVC and EPDM cannot survive these conditions, but BTL offers several products designed to withstand 20 years of continuous UV exposure ( AquaArmor RPEL-30, AquaArmor BTL-40, and AquaArmor PPL - 45 for example). There really is no practical alternative if you’re in for the long haul.

With a clear view of the benefits and disadvantages of each of these liner materials, you should have a better idea of what’s right for your project. For the best lifetime performance and durability, a multi-layered RPE from BTL’s AquaArmor line is likely to be ideal for most any project on your golf course. If you’re still wondering which specific liner product will best meet your needs in a particular situation, reach out to us here at BTL Liners for more help.