EPIC System - Frequently Asked Questions

EPIC Engineering Q&A

1. Can this system be adapted to cold climates? What about winterization, and frost heaves?

Initial technical development of the EPIC design actually had its birth in Western New York, so the brutality of winter conditions have been well observed with no negative affect on the design. Water distribution is by gravity, and it is not a pressurized system where freezing water enclosed in a pipe expands and breaks the pipe simply because it has nowhere else to go. The EPIC chamber has an open bottom, and the six-inch high arch never has water content deeper than the bottom three inches. The short connection stubs made of 2" Schedule 40 PVC pipe simply transfer water from Chamber to chamber and are never full of water. Winterization is a simple act of shutting off the water supply source or flicking the switch that supplies the power to the recirculating pump. There is no need to blow out any pipes, and the system simply works as a drainage system as the plants and grass become dormant. If it's a dry winter even the residual water left in the EPIC chambers gets absorbed into the sand matrix from which it slowly evaporates from the upper level if above freezing, or sublimes if below freezing. Frost heaves do not appear to be a reality because as ice crystals form in the damp sand, there is enough void space in the matrix to accommodate the expanding ice crystals without pushing the soil mass out of shape. Additionally frozen sand remains highly porous and melts easily should winter rains become a reality after a cold spell. Liquid water has enough heat retention to melt the frozen ice crystals in the sand, and the system quickly goes to the drainage mode as the 2" connector pipes were already free and clear of ice by design. A working roof top garden on top of a Minneapolis, MN ten story building has been functioning flawlessly for now over four years - need we say more?

2. Are there problems with root intrusion?

Root growth in EPIC systems appears to be naturally limited to the 10" - 12" capillary zone. Root growth is prolific in this zone because oxygen and moisture levels are always in an ideal balance in an uncompacted sand matrix. Roots become minimal in the saturated zone because it is simply too wet with a diminished (but not anaerobic) oxygen content. Roots will hug along the exterior surface of the EPIC chamber, but are restricted naturally to enter the interior of the chamber because of the offset hole placement. In order for a root to access the interior, the root tip would first have to grow sideways through the exterior EPIC hole, then make a sudden 180-degree upward growth, and then continue upward through air or soil-less water and access the second inner hole all of which are located within the saturated zone. Physically and biologically this is not a natural event. The presence of roots around the exterior holes does not diminish but actually improves the capillary dispersal of water, the intended function of the design. In ordinary applications, EPIC beds themselves are designed to grow grass and shallow rooted shrubs and small trees. Large trees that may be part of EPIC systems in landscape projects are actually planted between EPIC liner pans so the deeper and invasive tap roots can continue to wander below and along the sides of the liner pans. Another procedure is to install individual liner pans (one per tree) 3'-4' below the surface under the tree ball thus only providing drainage and irrigation for the individualized tree. This procedure has applications for new orchards, vineyards, or tree-lined streets in urban areas where even ordinary street runoff water can be intercepted and diverted to feed the system.

3. Have you experienced rodent damage?

To date we have not noticed rodent damage in our installations including a garden bed installed over a known area of vole tunnels. Although a rodent could start to burrow from above into the damp sand, at 10" below the surface it would encounter the saturated zone with the consistency of quick sand. The tunnel would collapse, and the soaked environment would not be attractive as a habitat. Tunneling below the liners might occur in border areas of EPIC beds, but the liner may simply provide a ceiling limit for the tunnel, as there is no real incentive for a rodent to gnaw a flat plastic liner. However if a hole is somehow breached from below, the tunnel would quickly fill and self-seal with the slurry of wet sand. Because EPIC beds are modular interconnected units, severe damage (i.e. meteoroid strike) to one cell does not affect the entire field. A problem cell will demonstrate a "sink hole" condition at the point of damage and the subsequent unit will show signs of drought stress, as the water may be being short-circuited. Problem cells are easily dug up, repaired or replaced, and the same sand is reused after repair.

4. Any damage from aeration tines?

The standard yard or athletic field design calls for an overall depth of 13"-14", which still provides a 7"-8" cover of sand over the crown of the EPIC chamber before seeding or sod placement. A six inch tine would not damage the chambers, however the recommended tine length is 3"-4" such as a Ryan L28.

EPIC Engineering Q&A

1. I plan to use this as a substitute for a sand filter system used for stormwater quality treatment at the bottom of a dry detention basin. The first 6 inches of the basin will be water quality with the EPIC system and a 2" outlet then the remaining pond storage volume above the first 6" will exit the pond through a normal outlet structure to meet detention requirements. I think it will be a good replacement for the sand filter system because it is not as deep therefore it will cost less in this application. Is this what you envision to be a possible use of the EPIC system?

Yes it is a great use and this practice is being adopted by “The St. Paul Ports Authority” as they do not want anymore wet ponds because of liability issues. The EPIC™ system must be a minimum of a 15” profile or else the sand will be soggy and soft. An analogy would be the waters edge of a sandy beach. No structural strength. Moving up the beach you get to a much more stable section and moving up further you get into the dry sand. I would incorporate more 2” outlets in a header to the structure if you want to sand filter more water than what one 2” orifice allows.

2. You mentioned manifolds between the EPIC chambers? What is the diameter or size of the manifolds?

Any size you want but larger pipe size tees get expensive. We use 4” and 6” PVC pipes with 4”x2” or 6”x2” tees.

3. Are they sized large enough to equalize the flow of water across the system or is each chamber fit with an orifice and acts as its own mini detention basin?

The EPIC connection pipe between chambers is always 2”. Anything bigger will increase velocities of the flow and may cause piping or sand movement. Each pan and chamber does act as a mini detention basin with a raised 2” outlet.

4. You mentioned if it clogs you can maintain it by aerating and "picking up cores." What does "picking up cores" mean?

Replacing the grass and sand? No, in specialized applications (golf greens or sports fields) the core remnants can be picked up, vacuumed up or swept up. We also use a Kor –Topmaker which can remove the top 2” of a grass surface.

5. Do the subsurface outlets have to be placed at the bottom of the EPIC system or above the bottom such that there is always water beneath the subsurface?

No, we do not have a zero drain in civil engineering applications. Possible in high profile sportsfield projects in wet climates where a zero drain may be desired.

6. Is aeration absolutely required or is it just a recommendation?

It is a recommendation for opening up the thatch to exchange CO2 and O2 if thatch build up or “black layer (BPL) or anaerobic activity” develops.

7. You mentioned contractors experienced in EPIC system installation....are there any in western New York State?

Or is it easy enough to install such that a representative from Rehbein need not be present during installation? We would like to be present if a contractor has not been through our training and wants to get certified. These systems are simple to install but there are definitely important concepts and construction methods to follow. We have gained much experience in installing the EPIC™ system and the company never wants a poor installation.

8. When did you receive the patent for the EPIC system?

July 13, 1999, with new improvements accepted March 29, 2007. System refinement has been going on since 1986.

9. Approximately how many EPIC systems have been installed so far?

100(+) systems of varying sizes. Have any needed to be removed or replaced for any reason? One field was not maintained well and was top dressed inappropriately over time with clay as the grounds person maintaining the field wanted artificial turf. Eventually he was granted his request and artificial was laid right over the EPIC™ system. This opened up a whole new market for us. Making lemonade out of lemons. The EPIC system, as a base for artificial turf, helps cool the intense heat felt on artificial surfaces. Eventually when artificial turf needs to be replaced the client has the option to reseed the EPIC™ system and return the field into natural grass.

10. Summarize how the EPIC system works. At its simplest, the EPIC™ system integrates the first pipe specifically designed for sand.

The EPIC chamber creates a non-pressurized, gravity flow path of least resistance for water to migrate through a medium washed sand profile. The EPIC system works like this: rather than allowing water to run off any type of surface--parking lots, roofs, driveways, football fields--the gravity based EPIC™ system (essentially a network of underground reservoirs) captures and filters stormwater runoff at its source and stores the water for irrigation. By using a layer of porous sand beneath the surface of the turf, the EPIC System™ draws and filters water to an underground storage area created through the combination of chambers, pans, and PVC pipes. From this, water can then be wicked up by capillary rise through the same sand to the plant roots, thus taking care of [all] irrigation needs. Therefore, while relying on zero moving parts and on an efficiency of 100%, this single product provides superior drainage, irrigation and phenomenal stormwater management benefits to a water resources industry hungry for real solutions. The EPIC™ system has truly turned stormwater management “upside-down”.

11. Is all the harvested rainwater taken up by plant roots or is there an outlet to a conventional storm sewer system or holding tank?

Yes there are outlets. Optional supplemental water storage underneath or adjacent to the EPIC system can be added to harvest water for irrigation use in warmer months. Water filtered through the sand profile drains to a final outfall. Depending on your hydraulic or hydrological design you need to design in a 2” outlet or multiple 2” outlets. If too many are needed they can be manifolded together to discharge through larger drainage pipes. Largest one so far is a six inch or multiple 4” PVC pipes. Also very easy to model using HydroCAD.

12. How much maintenance does an EPIC system require (besides mowing the lawn)?

Regular aeration, fertilization, overseeding, pesticides, and fungicides as awareness of landscape condition dictates. Biological growth is very prolific. Lawns grow so well that you need to keep on top of your mowing. The water is distributed directly to the roots, and the concept of subsurface fertilization becomes a reality. Regular aeration in the Spring and Fall is advisable for the air exchange through the thatch. How often does the maintenance have to be done? As often as regular scheduling demands. Golf courses mow 6-7 times per week. Homeowners mow once or twice every 1-2 weeks. The more something is taken care of, the better it will look.

13. What is the approximate material cost of an EPIC system per square foot or yard?

Depending on chosen designs, EPIC material costs (less sand ,labor and site prep) are either $1.60 to $2.50 per square foot. Total costs for completed athletic fields have ranged for a 100,00 SF field you are between $6-$8/SF.

14. Are there any replacement parts required?

Systems can be designed with very small recirculating pumps from your storage tanks to the high point of the system. These are usually your small 1/6 to ½ HP pumps at Home Depot If so, how much are they? Starting at about $40 to a couple hundred dollars. In some manual or drainage applications the final system may not have any moving parts that need replacement.

15. The NYSDEC requires that any installed stormwater system in New York State remove at least 80% of the total suspended solids (TSS) and 40% of the total phosphorus (TP). Will the EPIC system do this?

If so, do you have field or laboratory tests of the runoff samples to demonstrate this so I can submit them to an approval agency and have them accept it? EPIC™ captures and quadruple filters sheet flow and stormwater runoff and slowly releases the excess downstream in a controlled manner. Every case is different as it is such a versatile system every application is different. In general the system will physically surface filter particle sizes that are 8 times smaller than the sand grain used. Suspended muddy water has been shown a clarity reduction from 670ntu to 82 - 100 ntu's (85-88%) in filter runs through typical profile depths of sand. Phosphorus reduction will be a function of TSS content and subsequent uptake by the growing plants in the system. Currently there is a test project at RCWD in MN. There is no data from the site yet, results will be posted.

16. Where can a contractor order this system from?

We are training interested contractors to install this system. If a contractor is not pre-certified, EPIC Green Solutions will provide supervision on every installation at the client's ultimate cost. We are the primary supplier in the world except for the North American and Carribean markets where Firestone Specialty Products are the exclusive distributors.

17. Approximately how long does the EPIC system take to install per square foot or square yard?

Depends on manpower and equipment used. Previous installations have shown a range of 4,000 SF per day for a 4-man crew, up to 20,000 SF per day for a five-man crew and specialized equipment.

18. Does the soil media ever have to be dug up and replaced?

No, the sand particles do not decompose, so the sand profile does not compact and remains stable indefinitely... unless surface plugging occurs by contamination of clays or silts over time. Regular aeration maintenance and collection of cores resolves the potential clay or silt issue.

19. Does the soil media only contain sand or is there some other proprietary ingredients in the media?

Bottom 2” are a #10 gravel and the rest is locally obtained concrete or mason sand. Sources are pre-tested to determine the true design profile height. Optional inoculation of oleophilic bacteria or other decomposing soil microbes can be inoculated in the profile on special biotreatment applications.

20. Is the system expandable?

Can more treatment area be added later? Yes, unless it is a closed system the system will need modification.

21. Is there an emergency overflow incorporated into the system in case of excessive stormwater surges?

Yes, always a recommended engineering practice.

22. Approximately how much volume of stormwater per square foot (or if more applicable, how many CFS of runoff flow per square foot) can the system accommodate before it overflows?

The system can hold about 2.5 gal/ SF of a 13” profile. Each 2” orifice can convey about 0.1 CFS. Optional additional pre-filtered storage can be added under the system in the form of various structures that create a void space. It all depends on the sand profile which can vary from 13 inches - 24 inches. A 24 inch profile can hold 4.5 gallons.

23. How do I design an EPIC system? If so, how much do you charge for the design service?

EPIC Green Solutions can help engineers design with the EPIC™ system. It is easily done and our modeling tool of choice (so far) is HydroCAD. EPIC™ systems are modeled as ponds with a stage vs. storage table which reflects what is happening in the soil and above the soil. Below the 2” inverts 1% porosity as it does not accept zero. Above the 2” outlet the void ratio is anywhere from 33%-47% porosity for the sand and the chambers and 100% storage above the grass or landscaped surface. We also do consulting work for local engineers at $100/hr.

24. Can a representative of EGS be on site during installation?

Yes, we highly encourage this unless the contractor is experienced in installations.

25. Do you have details you can send me (preferably in AutoCAD) so I can specify the EPIC system on my construction plans quickly?

Yes we have AutoCAD details which we can share. Please refer to the details & specs section of the website.

26. Do you have written specifications for the EPIC system that you can send?

Yes we have a specification which we can share. Please refer to the details & specs section of the website.

27. Do you have installation instructions for the EPIC system that you can send?

Yes we have a construction specification addressing all installation aspects we can share. Please refer to the white papers section of the website.

28. Do I have to incorporate the EPIC system into another treatment system such as at the bottom of a detention basin or can it detain stormwater?

It can detain stormwater but retrofitting a dry detention basin is a very important application. The St. Paul Ports Authority wants to get away from wet detention basins because of the liability issue. SPPA is putting in dry EPIC™ system detention systems where all the water is sand filtered. What's the maximum amount of stormwater it can possibly detain per square foot or per unit? Each chamber can drain approximately 0.1 CFS or what a 2” orifice can discharge. Manifolding the system is easy to increase your discharge to what you are allowed to discharge.