Biodegradable Woven Burlap Silt Fence for Trenchless and Trench Instalation and Method of Installing the Same

This application claims priority to U.S. provisional patent application Ser. No. 63/647,121 filed May 14, 2024, titled “Biodegradable Woven Composite Silt Fence” which application is incorporated herein by reference in its entirety.

The present invention relates to a silt fence and more particular to biodegradable woven burlap silt fences.

The present invention relates to silt fences that fit in the general and overlapping fields of erosion, sediment and pollution control. Erosion control, broadly, is the practice of preventing or controlling wind or water erosion in agriculture, land development, coastal areas, river banks and construction. Effective erosion controls handle surface runoff and are important techniques in preventing water pollution, soil loss, wildlife habitat loss and human property loss. Sediment control is a practice designed to keep eroded soil on a construction site, so that it does not wash off and cause water pollution to a nearby stream, river, lake, or sea. Sediment controls are usually employed together with erosion controls, which are designed to prevent or minimize erosion and thus reduce the need for sediment controls. Sediment controls are generally designed to be temporary measures; however, some can be used for storm water management purposes. Pollution control, in this context, is the removal or limiting of specific contaminants within surface waters, and pollution control devices may be implemented with or integrated within erosion and sediment control devices.

A silt fence is a temporary sediment control device used on construction sites to protect water quality in nearby streams, rivers, lakes and seas from sediment (loose soil) in stormwater runoff. Silt fences are widely used on construction sites in North America and elsewhere, due to their low cost and simple design. See Stevens, Ellen; Barfield, Billy J.; Britton, S. L.; Hayes, J. S. (September 2004). Filter Fence Design Aid for Sediment Control at Construction Sites (Report). Cincinnati, OH: U.S. Environmental Protection Agency (EPA).

A silt fence is often installed as a perimeter control, i.e. around a perimeter of an area of interest. They are often used in combination with sediment basins and sediment traps, as well as with erosion controls, which are designed to retain sediment in place where soil is being disturbed by construction processes (i.e., land grading and other earthworks). See “Chapter 2. Erosion and Sediment Control Principles, Practices and Costs” (PDF). Virginia Erosion and Sediment Control Handbook (Report) (3rd ed.). Richmond, VA: Virginia Department of Environmental Quality (VA DEQ). 1992.

A typical silt fence consists of a piece of synthetic filter fabric, also called a geotextile, stretched between a series of wooden or metal fence stakes along a horizontal contour level. The stakes are installed on the downhill side of the silt fence, and the bottom edge of the fabric is trenched into the soil and backfilled on the uphill side. The design/placement of the silt fence should create a pooling of runoff, which then allows sedimentation to occur. Water can seep through the silt fence fabric, but the fabric often becomes “blocked off” with fine soil particles (all sediment-retention devices have this challenge, and none of them “filter” storm water for very long). A few hours after a storm event, the fabric can be “disturbed” in order to dislodge the fines, and allow clean water to flow through. Depending on the protected watershed and erosion, larger soil particles will settle out, ultimately filling the silt fence to the top of the structure; requiring another silt fence above or below it (creating a new ponding area), or for the silt fence to be removed, the sediment removed or spread out, and a new fence installed. The fence is not designed to concentrate or channel stormwater. The fence is installed on a site before soil disturbance begins, and is placed down-slope from the disturbance area. See Silt Fences (PDF) (Report). Stormwater Best Management Practice. Washington, D.C.: EPA. 2012. EPA 833-F-11-008.

Silt fence fabrics (geotextiles) tested in laboratory settings have shown to be effective at trapping sediment particles. However, some field tests of silt fences installed at construction sites, have shown generally poorer results. In these studies, effectiveness testing involved measurements for both total suspended solids and turbidity. Other studies and articles about silt fence usage and practice document problems with installation and maintenance, implying poor performance. Since at least the year 2000, static slicing the material into the ground has been widely adopted. In 2000 the U.S. Environmental Protection Agency (EPA) co-sponsored silt fence efficacy field research through its Environmental Technology Verification Program, and in general, the report found the static slicing method to be highly effective, and efficient. It has been proposed by some that silt fence effectiveness is best determined by how many hundreds of pounds of sediment are contained behind a given silt fence after a storm event, and not turbidity, etc. as sediment-retention is the end goal, and not a water-quality measurement used in erosion control, for instance.

Silt fences may perform poorly for a variety of reasons, including improper location (e.g. placing fence where it will not pond runoff water), improper installation (e.g. failure to adequately embed and backfill the lower edge of fabric in the soil) and lack of maintenance—fabric falling off of the posts, or posts knocked down. During various phases of construction at a site, a silt fence may be removed relocated and reinstalled multiple times. See Brzozowski, Carol (November-December 2006). “Silt Fence Installation”.. Forester Media. 13 (7).

The proper use of silt fences can protect the environment during construction activities, however a silt fence that is not removed can themselves create a problem for the environment as often the geotextile is comprised of plastic.

Further, conventional silt fences can serve as a source for secondary microplastics in the environment. Microplastics are fragments of any type of plastic less than 5 mm (0.20 in) in length, according to the U.S. National Oceanic and Atmospheric Administration (NOAA) and the European Chemicals Agency. They cause pollution by entering natural ecosystems.

For background, the term macroplastics is used to differentiate microplastics from larger plastic waste, such as plastic bottles or bigger pieces of plastics. Two classifications of microplastics are currently recognized. Primary microplastics include any plastic fragments or particles that are already 5.0 mm in size or less before entering the environment. Secondary microplastics arise from the degradation (breakdown) of larger plastic products through natural weathering processes after entering the environment.

Silt fences that contain plastic geotextiles may be a source of secondary microplastics, and microplastics which are recognized to persist in the environment at high levels, particularly in aquatic and marine ecosystems, where they cause water pollution. However, microplastics also accumulate in the air and terrestrial ecosystems. Plastics degrade slowly (often over hundreds to thousands of years), thus microplastics have a high probability of ingestion, incorporation into, and accumulation in the bodies and tissues of many organisms. The toxic chemicals that come from both the ocean and runoff can also “bio-magnify” up the food chain. In terrestrial ecosystems, microplastics have been demonstrated to reduce the viability of soil ecosystems and reduce weight of earthworms. The cycle and movement of microplastics in the environment are not fully known. Deep layer ocean sediment surveys from 2020 in China show the presence of plastics in deposition layers far older than the invention of plastics, leading to suspected underestimation of microplastics in surface sample ocean surveys. See Xue B, Zhang L, Li R, Wang Y, Guo J, Yu K, Wang S (February 2020). “Underestimated Microplastic Pollution Derived from Fishery Activities and “Hidden” in Deep Sediment “.&54 (4): 2210-2217. Microplastics have also been found in the high mountains, at great distances from their source. See “No mountain high enough: study finds plastic in ‘clean’ air”.. AFP. 21 Dec. 2021. Microplastics have also been found in human blood, while their effects remain largely unknown.

It is one object of the present invention to provide an efficient and cost-effective silt fence that minimizes its own detrimental effects on the environment.

This invention is directed to a cost effective, efficient, and easy to implement biodegradable woven silt fences with stabilizing fins forming a bury depth indicator.

One aspect of the invention provides a silt fence comprising a plurality of spaced stakes; and a burlap geotextile with a weight greater than 15 oz. per square yard and less than 50 oz. per square yard comprising one of i) a single layer burlap material and ii) a composite burlap material having multiple burlap layers.

One aspect of the invention provides a silt fence configured for trenchless installation comprising a plurality of spaced stakes; and a single layer burlap geotextile with a weight greater than 15 oz per square yard and less than 50 oz per square yard and including an integral ground engaging apron.

One aspect of the present invention provides A trenchless method of installing a silt fence for erosion, sediment and pollution control, comprising the steps of: providing a silt fence bundle comprising a plurality of spaced wooded or metal stakes and a burlap geotextile with a weight greater than 15 oz per square yard and less than 50 oz per square yard comprising one of i) a single layer burlap material and ii) a composite burlap material having multiple burlap layers, with the geotextile coupled to the spaced wooded or metal stakes and including an integral ground engaging apron; driving the plurality of spaced wooded or metal stakes into the ground until the integral ground engaging apron is flush with the ground; and staking the ground engaging apron to the ground with staking elements.

These and other aspects of the present invention will be clarified in the description of the preferred embodiment of the present invention described below in connection with the attached figures in which like reference numerals represent like elements throughout.

The present invention is directed to a single layer biodegradable woven composite silt fenceshown inor biodegradable woven composite silt fence, shown in. The biodegradable woven composite silt fenceis shown with trench engaging stabilizing finshaving a bury depth indicator. The silt fencewill include a composite woven geotextilecoupled to stakesby staplesor the like provided at′ intervals. The silt fencewill include a single layer woven geotextilecoupled to stakesby staplesor the like provided at′ intervals.

The woven geotextileis asymmetrical burlap composite. Composite within the meaning of this application defines multiple layers to the geotextileacross its operative surface, with each layer formed of woven burlap material (such as three leading burlap layersand two trailing burlap layers). Woven defines fabrics formed of interlaced threads. Woven burlap fabric is fabric woven from vegetable fibers such as jute, hemp, sisal, or similar natural fibers.

Burlap fabric, also known as Hessian fabric, or Crocus fabric in the Caribbean, is generally considered dense woven fabric, historically coarse, more recently produced in a more refined state, the refined version is sometimes known simply as jute, and is well established as an eco-friendly material. Burlap comes in different types, weights or grades and colors. Color is not critical for the woven geotextileother than possibly to increase visibility of the silt fenceminimizing the likelihood of people (i.e. construction workers on construction equipment) accidently damaging the silt fence, but cost is a critical factor in having users adopt the silt fence. The grade or weight of burlap for the layersandforming the asymmetrical burlap woven geotextileis important in the silt fence. Conventional burlap fabric comes in different weights ranging from 5 to 11 oz (generally measured as weight/square yard). The higher the weight, the tighter the weave. The preferred embodiment of the invention uses a woven geotextileformed of three 7 oz burlap layerson the leading or upstream side (i.e. facing the flow of water) and two 10 oz burlap layerson the trailing or downstream side.

The composite geotextileis considered asymmetrical because the layers (three 7 oz layersand two 10 oz layers) are arranged asymmetrically along the flow path. A symmetrical arrangement would have, for example, all the same weights for the layers, or the same weight for the leading one or two layers as the last one or two layers, or could be a single layer and be symmetrical.

Without being limited by theory, the initial layersserve effectively as a pre-filter with the central “core” of a 7 oz layerand a 10 oz layer. The outer layers also serve to protect the core without detrimentally inhibiting flow characteristics of the geotextile. The five layer structure allows for a controlled deterioration or degradation of the geotextilein the field without hindering performance.

The layersandof the composite geotextilemay be treated such as with animal fat to improve lifespan and performance of the geotextile. Other ecologically friendly treatment materials may be used such as vegetable oils or lanolin. It is desirable that the surface treatment for the layersand, if any, be ecologically friendly.

The woven geotextileis a single layer burlap material. Single layer within the meaning of this application defines only a single layer to the geotextilesubstantially across its operative surface. In other words the inclusion of beltingat the top does not transform the single layerinto a composite component for a silt fence. The single layer of geotextileis formed of woven burlap material. Woven defines fabrics formed of interlaced threads. Woven burlap fabric is fabric woven from vegetable fibers such as jute, hemp, sisal, or similar natural fibers. As noted above, burlap comes in different types weights or grades and colors. Color is not critical for the woven geotextileother than possibly to increase visibility of the silt fenceminimizing the likelihood of people (i.e. construction workers on construction equipment) accidently damaging the silt fence, but cost is a critical factor in having users adopt the silt fence.

The grade or weight of burlap forming the woven geotextileis important in the silt fence. As noted above, conventional burlap fabric comes in different weights ranging from 5 to 11 oz. (generally measured as weight/square yard). The preferred embodiment of the invention uses a woven geotextileformed of 17 oz sagless burlap It is well known that to utilize 17 oz sagless burlap in upholstery applications and in upscale furniture design.

The surfaces of the geotextilemay be treated such as with animal fat to improve lifespan and performance of the geotextile. Other ecologically friendly treatment materials may be used such as vegetable oils or lanolin. It is desirable that the surface of the geotextile, if any, be ecologically friendly.

A belting and visibility stripformed by a 4″ wide strip of natural fiber material folded over the top of the geotextileand sewn thereto may be used as reinforcing belting for the fence. The stripserves as a reinforcing member, an aid in geotextile assembly, and a visual indicator of the top of the fence. If the stripis made from a high visibility color, such as yellow or red or neon green or the like, it will add another safety feature minimizing the accidental interference with the silt fenceduring construction activities (e.g., accidentally running over the fencewith construction equipment, or placing stored construction materials on the fence). The minimization of the accidental knocking down of the silt fencecan also be broadly categorized as improving the operation of the fence.

Fenceincludes a belting stripformed by a 4″ wide burlap strip folded over the top of the single layer geotextileand sewn thereto. The burlap stripserves as a reinforcing member, and a visual indicator of the top of the fence. If the burlap stripis made from a high visibility color, such as yellow or red or neon green or the like, it will add another safety feature minimizing the accidental interference with the silt fenceduring construction activities as detailed above.

The woven geotextile silt fencefurther includes trench engaging stabilizing finsformed by wooden plate with a bury depth indicatorat a top thereof. The stabilizing finsare easily formed by attaching a wooden rectangular plate body to selective, possibly all, stakesopposite the side coupled to the woven geotextile. The length of the wooden plate body forming finsis preferably less than the depth of a conventional silt fence trenchin the groundand the width is less than 2 times the width of the stake, preferably about 1.9 times the width of the stake. The finsare the portion of the body of the plate extending beyond the stake. This size makes the finseffective but not unwieldy or costly. The plate body forming finswill engage the wall of the trenchduring installation and the finswill add a stabilizing resistance preventing the fenceand stakesfrom being pushed over and out of position by ponding water and the like on the fabricor on the fenceas a whole.

In addition to the stabilizing fins, the top horizontal surfaceof the plate body forming finsacts as a visual bury depth indicatorfor the stake. Users can quickly visually see how far to position the stakein the ground, namely when the top surfaceof the plate body forming fins(also the top surface of the fins) is even with the top of the ground in the trench. As the finsis less than the depth of the trench, the plate body forming finsdoes not increase insertion resistance for the stake, and a rectangular shape for the plate body forming finsis effective without causing other detrimental problems. The body forming finsfor fencemay be made of metal or wood to be ecologically friendly (by avoiding plastic), but wood may be most cost effective.

The single layer woven geotextile silt fencefurther includes stabilizing finsformed by triangular wooden plywood plate (⅛″-⅝″ thick generally) with a bury depth indicatorat a top thereof shown in. The stabilizing finsare easily formed by attaching the wooden triangular plate body to selective, possibly all, stakesopposite the side coupled to the single layer woven burlap geotextile. The length of the triangular wooden plate body forming finsis preferably less than the depth stakeand the width is less than 2 times the width of the stake, preferably about 1.9 times the width of the stake. The finsare the portion of the body of the triangular plate extending beyond the stake. This size makes the finseffective but not unwieldy or costly.

The single layer woven geotextile silt fenceis configured for trenchless installation whereby the stakesare typically driven into the ground and the triangular plate body forming finsis shaped to easily penetrate the ground during installation and the finswill add a stabilizing resistance preventing the fenceand stakesfrom being pushed over and out of position by ponding water and the like on the fabricor on the fenceas a whole.

In addition to the stabilizing fins, the top horizontal surfaceof the triangular plate body forming finsacts as a visual bury depth indicatorfor the stake. Users can quickly visually see how far to drive the stakein the ground, namely when the top surfaceof the triangular plate body forming fins(also the top surface of the fins) is even with the top of the ground.

The stakesandfor fencesand, respectively, may be made of wood or metal, but wood is deemed most cost effective. The plate body forming finsmay be nailed or otherwise attached to the individual stakes. Metal staplesare shown coupling the geotextileto the stakesand are shown angled to minimize tearing of the fabric.

The multi-layer structure of the composite geotextileallows for the silt fence to be used in a conventional bury mode (trench mode), as shown, with about 12″ of the geotextilebelow grade in trench. Some applications desire the fenceto be installed in a trenchless configuration or apron mode (not shown) analogous to the trenchless implementation preferred for fencedescribed below in which the otherwise buried portion of the geotextileis laid on the ground facing the flow of water and preferably secured to the ground, such as with staples. The multi-layered structure of the geotextileallows for the fenceto be implemented simultaneously in both a trench mode and an apron mode as shown in. In this apron and bury mode the leading layersof the fenceare used as an apron on top of the ground (preferably secured by staples) while the trailing two layersare in bury or trench mode. An attaching line of stitching at a bury or apron line (e.g. 12″ up from the bottom) is helpful to allow for this installation. The trench and apron mode ofis a subset of a trench installation as the trench must still be formed.

The height of the geotextileabove the grade is 18″-28″ (without fence backing), preferably 24″ with 12 inches as below grade for bury or on grade apron or both as shown. The geotextile could extend to 36″ above grade if coupled with a reinforced backing, typically a chain fence, but the 18″-28″ is preferable.

One of the main purposes of any silt fence is to prevent the unwanted migration of disturbed soil during construction. The trenchthat buries the lower part of the fabricof the fenceis utilized to prevent water creating a path under the fencebypassing the fabric. However, this installation process creates extra disturbed soil that adds to the disturbed soil load of the fence. More significantly, this installation requires trenching tools and labor.

show a trenchless installation of the fencethat minimizes the installation time and soil disturbance without effecting operation of the fence. There are several advantages to the trenchless installation shown in. The first is the equipment needed to install the fenceis merely sledgehammer, utility knife, and staple guns for staples(or tool for wire ties if used) and apron staples,and(discussed below). There is no trenching equipment required or disturbed soil.

In the trenchless installation the stakesare driven into the ground with a sledge hammer, and as shown inthe top surfaceof the plate bodies can also be used as a depth of driving guide. The plates may be positioned without the top surfaceforming a guide so as to be completely buried as shown in. In this method of installation the plate is preferably beveled on the bottom (triangular in shape) as the stakeswill be driven into the soil. A preferred shape for plates when the stakes are driven into the ground such as in a trenchless installation is shown in. The plate still provides stabilizing finsfor the fence.shows preferred wooded stakeswith preferred staplesas fasters, whileshows the use of metal t-posts forming stakesand wire ties for fasteners.

With the stakesdriven into the ground, the lower portionforms a ground engaging apron that is secured to the ground through staking elements,and. The plurality of spaced wooded or metal stakesare driven into the ground until the integral ground engaging apronis flush with the ground. Preferably the staking elements,andare 1″×6″ staples. The apronis preferable about 12″ in length. The staking elements,andinclude a line of staplesevenly spaced along the leading edge (the distal edge of the fabric) of the apronwith about 6″ proving to be an effective distance. The distal end of the fabricis the end spaced from the top coupling strip, which is considered the leading end of the apronas it faces the upstream side of ground. The staking elements,andinclude a groupings of about four staplesevenly spaced along the trailing edge of the apron. The trailing edge of the apronis spaced about 12″ up from the distal end of the fabric, and about 6″ between the staplesin the grouping proving to be an effective distance and the grouping being centered between the stakes. The staplesandare preferably positioned perpendicular to the line of the fencewhereby the head of the staples extend generally perpendicular to the plane of the upper portion of the fabricon the stakes.

The staking elements,andinclude a groupings staplesspaced along overlapping portions of apron.is a perspective schematic view of an inside corner of the fenceformed with the trenchless installation method according to one embodiment of the present invention. The user cuts the apronatand overlaps the apron in the inside corner and adds staplesto hold down the overlapped portion.is an elevated plan view of a′ pre-staked bundle of a geotextile silt fencewith stabilizing features and′ stakes according to one embodiment of the invention showing a flapon one edge of the bundle. When adding a second bundle for a fence installation the flapof one section is overlapped with the other end (stakewithout plate) and the a grouping of staking elementswill be used in the overlapped portion. Further the upper portion of the flap can be coupled to the end stake of the adjacent bundle via staples(generally ¼″×1″).

The single layer 17 oz sagless burlap fabricof the fenceis particularly well suited for trenchless installation but this method may be applicable to other silt fences assuming they can achieve a solid engagement with the ground and prevent water from undercutting beneath the fence.

The use of metal posts for stakesis well suited for an alternative trenchless installation in which the unbundled metal stakes(no fabricyet attached) are driven into the ground and the fabricwith apronis later attached to the stakesin situ with ties as fastenersand the apronis secured to the groundstaking elements,andas discussed above. The in situ installation may also be used with wooden stakes.

In the silt fenceas shown, above grade, the three 7-ounce layersfacing the water are more open and form a lofted/thicker/fuzzy pre-filter to entangle and collect solids before getting to the tighter 10 ounce layersin the back. This feature gets better over time because the looser weave 7 ounce burlap layerfibrillates (gets fuzzy) over time as it wets and dries. This helps with pre-collecting solids and should enable better blinding resistance at the 10 ounce layers. Further, it's better to have the stronger textile (e.g., 10 ounce layers) in the back to resist the bulge/push. This concept may be referenced as collective resistance and has been used in other silt fences using a scrim backer.

The silt fence, primarily below the grade in trench installations, is designed to fight rot from the outside in as it is expected that the outer layers will rot first. Over time, it is expected that that the inner 10 ounce layerand the inner 7 ounce layernext to it to be the last strength survivors. Once below grade fully rots, the geotextilewill likely tear at the bury line and effectiveness of the fenceis largely finished. The silt fenceis designed to resist that for as long as possible and the fenceas described and shown is expected to be at least 9 to 12 months in the field.

Regarding weight, the geotextilesandof the silt fencesandneeds to be under 50 ounces per square yard, preferably less than 45 ounces per square yard. The geotextilesandhave a weight greater than 15 oz per square yard. The fenceas shown and described has a geotextile about 41 ounces per sq yard (three 7 ounce layersplus two 10 ounce layers) and the fencehas a geotextile about 17 ounces per sq yard. With a textileof 36-inch tall, for the fencethat's about 13-14 ounces a linear foot of fence. Exceeding these upper weights makes the resulting fenceorgenerally nonviable with too much sagging. The asymmetric design of the geotextileof the fenceand the single layer geotextile of fenceaddresses weight advantageously.

It is apparent that many variations to the present invention may be made without departing from the spirit and scope of the invention. The present invention is defined by the appended claims and equivalents thereto.