Abstract:
The present application relates to systems and methods for making and using sediment barrier. More specifically the present application relates to systems and methods for using sediment barriers to reduce pollution of rivers and streams from sediment resulting from soil erosion at, for example, a construction site or other area of potential soil erosion. The sediment barrier typically includes at least one apron that serves to provide filtering, water velocity reduction and/or anchoring. The sediment barrier further includes a body portion that provides substantial filtering of sediment from water passing therethrough. The apron and/or body portions of the barrier are preferably composed of biodegradable material.

Description:
BACKGROUND 
   This application relates to systems and methods for removing and trapping sediment entrained in moving water so that the sediment does not enter and pollute the local streams and rivers network. Such systems are typically called “check dams” or sediment barriers. More specifically, the invention relates to biodegradable modular structures from which sediment barrier structures may be constructed. 
   It is very common to see bare soil slopes and drainage waterways near highways and constructions sites. When water flows quickly over exposed soil waterways and down slopes before vegetation covers the bare soil, the flow erodes the soil and carries the eroded soil and deposits the soil as sediment in surrounding natural waterways. If these sediments were not removed before they reached the natural waterways, they would pollute those waterways. Therefore, effective sediment control has become a major task in construction sites. To protect natural watersheds from polluting sediment, regulatory agencies like the U.S. Environmental Protection Agency have toughened regulations and strictly enforced those regulations, which has added to the demand for sediment control devices. 
   Various types of sediment control devices are now available. However, conventional sediment barriers do not perform well on all three factors. Conventional devices for controlling erosion and sediment on construction sites include sediment barriers made of hay bales, silt fences, rocks, stuffed fiber rolls, and a silt barrier with a triangular cross section (e.g., U.S. Pat. No. 5,605,416). These dams are placed at regular intervals in drainage ditches and on slopes to reduce the velocity of the water flowing over and through them and remove sediment entrained in the water. 
   The effectiveness of a sediment barrier structure is determined by, among other factors, its ability to: (1) remove a large percentage of sediment from water flowing through and/or over the dam, (2) accumulate a large volume of sediment before its ability to remove sediment degrades, and (3) become quickly integrated into the environment without interfering with the natural processes of the ecosystem in which it is installed. Efficiency, eco-friendliness, and cost are important factors to consider when selecting sediment control devices. Efficiency of a sediment control device relates to how well it blocks or traps sediment while allowing sediment free water to pass through and to the length of its functional life. Failure to account for functional life of a sediment control device could lead to serious problems during its applications. 
   Conventional sediment barriers do not perform well on all three factors. For example, sediment barriers made using fabric silt fences clog easily. The water flows through the fabric in the direction approximately perpendicular to the fabric surface and sediment collects in the fabric. Because the fabric is thin, it has little capacity to hold sediment before the spaces between fibers in the fabric becomes clogged. 
   In addition it is not that easy to remove a sediment barrier once sediment is deposited on it. Rock sediment barriers do not promote vegetation and they look very ugly in the middle of a waterway or on a slope in which vegetation has started to grow. Rock dams are also very hard to maintain since rocks tend to move when subjected to heavy flow conditions. 
   Dams made using hay bales or stuffed fiber rolls sometimes permit water to flow under the dam structure, which is sometimes called “under cutting.” Under cutting compromises the effectiveness of the dam because the water flowing under the dam erodes the soil under the dam and creates an unimpeded flow path. If the erosion caused by under cutting is severe, the velocity and volume of water flowing under the dam may cause the dam to fail. 
   Additionally, many conventional sediment barriers do not promote the growth of vegetation on and/or near the installation site. Because conventional dams either completely block the flow of water through them or quickly clog with sediment, a “pond” forms behind the dam soon after it is installed. The water in the pond impedes growth of most vegetation in the soil covered by the pond. Moreover, as rain and other sources of water flow into the pond at varying rates, the size of the pond behind a conventional dam changes. As the pond covers more soil, it may kill vegetation that had previously started growing on “dry” soil. A long dry spell can let the pond drain and allow vegetation to grow. However, if a new pond forms, the vegetation may die. Therefore, conventional sediment barriers typically impede growth of vegetation in the area behind the dam. 
   Virtually all sediment barriers in the form of continuous barriers and diversion dikes are quickly buried under the accumulated sediment that they remove from passing water. Whenever a buried sediment barrier is made of materials that are not 100 percent biodegradable, the dam must be removed soon after the dam stops removing sediment. Removing sediment barriers is labor intensive and expensive and disturbs the soil. Disturbing the soil increases the risk that erosion will recur at the site from which the dam was removed. Moreover, sediment-clogged sediment barriers are typically disposed of landfills, which consumes increasingly scarce landfill space. 
   SUMMARY 
   Sediment barriers described below perform as well as or better than conventional dams in connection with each of the three criteria described above. Such a sediment barrier reduces the velocity of flowing water at least as effectively as conventional dams. Such a sediment barrier also filters water more effectively than conventional dams by permitting sediment-bearing water to flow into and through the aprons and body of the barrier. The sediment barrier filters water in its body and an apron that mostly lays flat on the surface surrounding the body of the barrier. The upstream apron of the sediment barrier prevents the under cutting (i.e., water flowing under the dam) by covering and protecting the soil immediately upstream of the body from erosion. Additionally, the upstream apron filters and collects sediment from any water that may flow through that portion the apron. Therefore, any small flow through this portion of the apron will cease when sufficient sediment has been deposited in the apron to obstruct any such flow. The sediment that collects in the upstream apron also tends to anchor the apron and therefore the barrier in position. When sufficiently high volume flow is present, water will flow through and/or over the body of the barrier. When sediment-bearing water overflows the barrier, the downstream portion of the apron collects additional sediment in substantially the manner described in connection with the upstream portion of the barrier. 
   A sediment barrier as described below lets water flow through the barrier more readily than conventional barriers. When water passes through the barrier, the barrier filters the water and collects sediment inside the body and apron. Because water can flow through the barrier, the water behind the barrier does not rise as fast or reach the same level that it would if a conventional barrier were installed. The apron in the barrier having a fiber core begins collecting sediment from the upstream flow immediately. The apron collects some of the sediment by filtering the sediment from flow through the apron core. The apron also collects some of the sediment through friction between the flowing water and the surface of the upstream apron. This friction slows the flow enough that some of the heavier sediments settle out. The body of the barrier further slows the water flow by presenting a semi-permeable physical barrier to the flow. The body core permits some water to pass at very low relative velocities and filters sediment in the process so that water passing out of the downstream side of the barrier is substantially free of sediment. 
   Because the sediment barrier structures are constructed of biodegradable materials, they need not be removed from the installed location. Sediment barriers made with the modular structures also promote the growth of vegetation in and near the area in which the sediment barrier structure traps sediment. As vegetation grows in and near the sediment barrier, the barrier&#39;s ability to collect sediment is enhanced and the sediment barrier is integrated faster into the surrounding ecosystem. 
   When water flows at high enough rates to exceed the filtering capacity of the barrier, water flows over the top of the barrier (i.e., the top of the body) and contacts the downstream portion of the apron. The downstream portion of the apron includes a core made of coir fiber mat material covered with netting woven of coir twine. When the sediment-bearing flow reaches the downstream portion of the apron, that portion of the apron removes sediment in substantially the same manner described above in connection with the upstream portion of the apron having a fiber core. 
   One hundred percent of the material in the described barrier is biodegradable natural material. The preferred material is coconut fiber (coir) which is durable. Therefore, when sediment is deposited on the upstream apron it is not required to be removed at the end of the project. When it is use in the field, the described barrier does not create an upstream pond. This leads to quick drying in the surrounding area allowing vegetation growth without problem of water logging. It also eases movement of construction equipment without getting into wet soils. A rough surface of the aprons, especially downstream, breaks the flow velocity and trap sediment, if any. Furthermore, since current invention is made of one hundred percent natural biodegradable material, it does not require removing at the end of a project. This allows vegetation to grow on its aprons as well as the body as soon as it is installed. Furthermore, it does not need to be disposed in to a landfill at the end of its functional life. It can be left at the site or bury in the soil. Furthermore, when it is used with conjunction with vegetation, it assists the growth of vegetation by providing mulch, which retains moisture, from its decomposition at the end of its functional life. 
   Briefly, a sediment barrier as described includes one or more barrier segments, each of which includes substantially cylindrical body or roll attached to an apron. The body is attached to the apron such that the apron extends laterally from both sides of the body along substantially the entire length of the body. Alternatively, the apron may extend laterally from only one side of the body. A sediment barrier structure may be made in any length by connecting sediment barrier segments end to end. 
   The body includes a core of a substantially cylindrical bundle or roll of densely packed biodegradable material, preferably coconut (coir) fibers. The body is preferably a circular cylinder. However, other cylindrical or non-cylindrical shapes may be used. The body core is covered with a loosely woven netting of coir twine. The netting covering the body is woven of coir twine with a preferred spacing of about one to three inches. 
   The apron preferably also includes a core that is preferably a mat of densely packed biodegradable material, preferably needle-punched coir fibers. Most, if not all, the apron core is surrounded by a biodegradable netting, preferably woven of coir twine with a spacing similar to the spacing in the netting that surrounds the body core. In a preferred form, the netting that surrounds the apron is an extension of the netting that surrounds the body. Alternatively, portions of the apron may have no coir fiber core. Such portions are preferably constructed of a netting, preferably coir netting, having a tighter weave between the warp twine than the netting used to cover the portions of the apron having a core. A preferred spacing between the warp twine is about ¼ to ⅓ inches. 
   The body is connected to the apron by tying the netting that covers the body to netting that covers or constitutes the apron at points along one or more approximately linear paths extending in the same direction as the longitudinal axis of the body. The body is preferably connected to the apron along two or more such longitudinal paths and is more preferably connected along at least three longitudinal paths. 
   The foregoing general description and the following detailed description are exemplary and explanatory only and do not restrict the inventions as claimed below. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more systems and methods and together with the description, serve to explain the principles espoused in the present application. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front schematic perspective view of a sediment barrier segment. 
       FIG. 1A  is a partial cross-sectional view of the sediment barrier segment of  FIG. 1  taken along line  1 A— 1 A of  FIG. 1 . 
       FIGS. 1B and 1C  schematically illustrate alternative ways to secure the body of a sediment barrier segment according to the invention to the apron of the sediment barrier segment. 
       FIGS. 2A–2F  are schematic end views of intermediate structures made when manufacturing the sediment barrier segment of  FIG. 1 . 
       FIG. 3  is a schematic end view of an alternative version of a sediment barrier. 
       FIG. 4  is a schematic end view of another alternative version of a sediment barrier. 
       FIG. 4A  is a partial detail plan view that schematically illustrates portions of the netting of the sediment barriers of  FIGS. 3 and 4 . 
       FIG. 5A  is a schematic end view of one way of installing the sediment barrier of  FIG. 1  in the bed of a drainage ditch. 
       FIG. 5B  is a schematic end view of another way of installing the sediment barrier of  FIG. 1  in the bed of a drainage ditch. 
       FIG. 6A  is a schematic end view of one way of installing the sediment barrier of  FIG. 3  in the bed of a drainage ditch. 
       FIG. 6B  is a schematic end view of another way of installing the sediment barrier of  FIG. 3  in the bed of a drainage ditch. 
       FIG. 7A  is a schematic end view of one way of installing the sediment barrier of  FIG. 4  in the bed of a drainage ditch. 
       FIG. 7B  is a schematic end view of another way of installing the sediment barrier of  FIG. 4  in the bed of a drainage ditch. 
       FIG. 8  schematic perspective view of two sediment barrier segments of  FIG. 1  that are mated to end to end form a sediment barrier structure. 
       FIG. 9  is a schematic elevation view of the upstream side of a two-segment sediment barrier structure installed in a drainage ditch. 
   

   DETAILED DESCRIPTION 
   This application refers in detail below to the exemplary systems and methods, which may be illustrated in the accompanying drawings. Wherever possible, the application uses the same reference numbers throughout the drawings to refer to the same or similar items. As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein and throughout the claims that follow, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     FIG. 1  illustrates a sediment barrier segment  10  according to the present invention that generally includes a body  11  and an apron  13 . The sediment barrier segment  10  has length L and width W. The body  11  is illustrated as a circular cylinder having diameter D and length L. However, the body  11  may have other cross sectional shapes (e.g., a square, ellipse, rectangle, or triangle, among others). The body  11  is attached to the apron  13 , which is illustrated as a mat having width W and thickness T. The apron  13  includes two portions, an upstream apron  13   a  and a downstream apron  13   b , each of which laterally extend along substantially the entire length of the body  11  from near the bottom of the body  11 . Alternatively, the apron  13  may include only the upstream apron  13   a  or the downstream apron  13   b . The body  11  and the apron  13  are surrounded by netting  18 , which is preferably woven of biodegradable twine (e.g., coir twine). The netting  18  may be woven of warp twine  16  and weft twine  17 . The body  11  is attached to the apron  13  at points along path  22  near the bottom of body  11 . The body  11  may also be attached to apron  13  at locations other than path  22 , which are not shown in  FIG. 1 , but discussed in more detail below. For additional strength, the body netting at the bottom of the body  11  may be stitched through the apron core  14  to the netting on the bottom of the apron  13 . 
   As illustrated in  FIG. 1A , the body  11  includes a body core  12 , and the apron  13  includes apron core  14 .  FIG. 1A  illustrates only the central section of apron core  14 . The body core  12  and the apron core  14  are made of biodegradable fibers  15 . The fibers used in body core  12  and apron core  14  are preferably coir fibers that permit water to flow through them while also filtering sediment from the water. As the fibers  15  filter sediment, the sediment collects in the spaces between fibers. The body core  12  and apron core  14  are encased within netting  18 . More particularly, portion  18   a  of netting  18  surrounds body core  12 , and portion  18   b  of netting substantially surrounds apron core  14 . As illustrated netting portions  18   a  and  18   b  are portions of a single piece netting  18 . Alternatively, netting portions  18   a  and  18   b  may be made from separate pieces of netting. 
   Netting portion  18   a  completely surrounds body core  12 . Netting portion  18   b  as illustrated extends from point  22  across the top of downstream apron  13   b , under downstream apron  13   b  and upstream apron  13   a , and across the top of upstream apron  13   a  to point  24 . Point  22  represents the end view of the path  22  illustrated in  FIG. 1  and described in the accompanying text. Point  24  represents the end view of another path  24  (not illustrated in  FIG. 1 ) at which apron  13  is attached to body  11 . Path  24  is located on the opposite side of body  11  from path  22 . Points  20  and  26  represent the paths at the bottom of body  11  and the bottom of apron  13  respectively along which the body  11  may be stitched to apron  13 . The path corresponding to point  20  extends along substantially the entire length of the bottom of body  11  in the plane including centerline C and the longitudinal axis of body  11 . The path corresponding to point  26  extends along substantially the entire length of the bottom of the apron  13  in the plane including centerline C and the longitudinal axis of body  11 . 
     FIGS. 1B and 1C  illustrate alternative versions of the attachment between body  11  and apron  13 . In  FIG. 1B , points/paths  22  and  24  are in the substantially the same locations as described in connection with  FIGS. 1 and 1A . However, apron  13  is attached to body  11  by stitching the bottom of netting portion  18   b  along point/path  26   a  through apron core  14  to point/path  24 . Apron  13  is also attached to body  11  by stitching netting portion along point/path  26   b  through apron core  14  to point/path  22 . In  FIG. 1C , the netting portion  18   b  surrounding apron  13  is tied to body  11  along point/path  22  as described in connection with  FIGS. 1 and 1A . Additionally, apron  13  is attached to body  11  by stitching the bottom of netting portion  18   b  along point/path  26   a  through apron core  14  to point/path  24 . 
     FIGS. 2A–2F  schematically illustrate intermediate structures made when manufacturing the sediment barrier segment  10  of  FIG. 1 . The sediment barrier  10  may be made by beginning with a piece of netting  18 , which is illustrated in  FIG. 2A . As illustrated, the width of netting  18  is apparent but not the length of the netting (which corresponds to length L of the sediment barrier segment  10 ). The netting  18  is also illustrated with point/path  22 , which divides netting  18  into portions  18   a  and  18   b . Portion  18   a  eventually will surround body  11 , and portion  18   b  will substantially surround apron  13 . Point/path  22 ′ corresponds to the edge of netting  18  that will eventually be tied to point/path  22 . Attaching edge  22 ′ on portion  18   a  is mated to point/path  22 , as generally indicated by moving edge  22 ′ in the direction indicated by the arrow R 1  in  FIG. 2B . When edge  22 ′ and point/path  22  are attached, portion  18   a  forms a space  12 ′ for body core  12 . As shown in  FIG. 2C , fibers  15  are stuffed into space inside portion  18   a  to form body core  12 . A group of fibers  15 ′ is left to protrude through portion  18   a  between points  22  and  24 . Apron core  14 , which is preferably formed of needle punched coir fiber matting, is positioned adjacent portion  18   b  as shown in  FIG. 2D . Portion  18   b  is wrapped around apron core  14  as indicated by moving edge  24 ′ in the direction indicated by the arrow R 2 , and edge  24 ′ is attached to point/path  24  on portion  18   a  as shown in  FIG. 2E . In this condition, fibers  15 ′ contact the top of apron core  14  (see  FIGS. 2E and 2F ). These protruding fibers  15 ′ assist in mating the body core  12  to the apron core  14  and ensure that no water can pass in the space between cores  12  and  14  without being filtered through coir fiber. The sediment barrier  10  is completed as shown in  FIG. 2F  by stitching the bottom of portion  18   a  to the bottom of portion  18   b  along point/paths  20  and  26  respectively. This stitching ensures that body core  12  and apron core  14  stay in close contact so that all water impinging upon the sediment barrier  10  is slowed and filtered. Once completed, sediment barrier segment  10  includes body  11 , body core  12 , apron  13  having upstream apron  13   a  and downstream apron  13   b , and apron core  14 . 
   One alternative form of the sediment barrier segment  10  is illustrated in  FIG. 3 , which is a schematic end view. In the illustrated alternative, the apron core  14  is positioned only in downstream portion  13   b  of apron  13 . The upstream portion  13   a  is formed by portion  18   b ′ of netting  18 . Another alternative form of the sediment barrier segment  10  is illustrated in  FIG. 4 , which is a schematic end view. In the illustrated alternative, the apron completely lacks apron core  14 . In the illustrated segment  10 , the entire bottom of apron  13  is formed by portion  18   b ″ of netting  18 . 
   As shown in the exploded schematic view of  FIG. 4A , netting portion  18   b ′ (of  FIG. 3 ) and netting portion  18   b ″ (of  FIG. 4 ) may be constructed using a tighter weave in which the spacing between twine  16  is smaller than the spacing between twine  17  and smaller than the spacing elsewhere in netting  18 . The spacing between twine  16  is preferably about ¼ to  1 / 3  inches, and the spacing between twine  17  is preferably between about 1 and 3 inches. This tighter weave in the netting portion  18   b ′ (of  FIG. 3) and 18   b ″ (of  FIG. 4 ) more effectively slows the water that flows over upstream apron  13   a  (in both  FIGS. 3 and 4 ) and in the downstream apron  13   b  (in  FIG. 4 ) than the more open weave of the rest of netting  18 . The tighter weave also increases the strength of the netting to increase the likelihood that the sediment barrier segment  10  remains anchored when water flows into the segment  10 . The alternative sediment barrier segments  10  illustrated in  FIGS. 3 and 4  contains less coir fiber  15  than the segment  10  illustrated in  FIG. 1  and therefore costs less to manufacture. 
     FIG. 5A  illustrates the segment of  FIG. 1  installed in the basin of a drainage ditch with water flowing in direction F. The segment  10  is anchored to the bottom of the ditch using four wooden stakes, two through the upstream apron  13   a  and two through the downstream apron  13   b .  FIG. 5B  illustrates an alternative way to anchor the upstream apron  13   a . Namely, the leading edge of the upstream apron  13   a  is buried in a trench, anchored using a wooden stake, and the trench is filled to bury the anchor.  FIGS. 6A and 6B  illustrate similar installations of the sediment segment of  FIG. 3 .  FIGS. 7A and 7B  illustrate similar installations of the sediment segment of  FIG. 4 . 
     FIG. 8  illustrates how two segments  10  may be positioned end-to-end to form a longer sediment barrier structure. The segments  10  mate along line  32  and a coir fiber blanket  30  is laid across the top of the joint between the two segments. The entire structure including both segments  10  and the blanket  30  are secured to the soil using wooden stakes. 
     FIG. 9  illustrates how a two-segment sediment barrier structure may be installed in a drainage ditch  40 . As in  FIG. 8 , two segments are mated end-to-end along line  32  and covered by coir fiber blanket  30 . The water level in ditch  40  indicated by dashed line  50  is sufficiently high such that water will flow over the top of the structure in area  60 . 
   The sediment barrier segments are sold in lengths of about 10, 15, and 25 feet with other lengths possible. The body  10  of the sediment barrier segment  10  is sold commercially in a circular cylinder form of 6, 9, or 12 inches in diameter. Other diameters are possible. The coir fiber  15  in the apron  13  and body  11  of the sediment barrier segment  10  provides structural stability and is an excellent medium for plant growth. After installation of a sediment barrier made using one or more barrier segments  10 , desired native plants may be planted on or around the barrier where plants can get sufficient water. With time, sediment will be deposited in and around the barrier, which creates an excellent medium for riparian vegetation. The densely packed coir rolls typically collect sediment for 2–3 years and then they blend naturally with the existing environment. 
   Every section of a sediment barrier according to the invention performs the function of filtering sediment from the water that contacts the barrier. Immediately after installation of a barrier segment  10 , the upstream apron  13   a  filters sediment from water that reaches that apron. As water accumulates behind the barrier and contacts the body  11 , the body filters sediment from the water as it flows through the body core  12 . Over time, filtered sediment accumulates in the upstream apron  13   a  and the body core  12 . The accumulating sediment slowly reduces the filtering effectiveness of the upstream apron  13   a  and the body  11 , which may cause the water level behind the barrier to rise enough to overflow the top of body  11 . When water flows over the top of body  11 , downstream apron  13   b  filters and collects sediment. Eventually, all three major parts of the barrier are impregnated with accumulated sediment. The accumulated sediment dramatically increases the weight of the barrier, which prevents water flowing into the barrier from dislodging the barrier. The accumulated sediment also serves as a very fertile base in which plants grow easily. As plants begin to grow in and around the sediment laden barrier, the plants consume the water adjacent the barrier. Eventually plants cover the entire area surrounding the barrier and water stops accumulating behind the barrier. At this point in time, the barrier is essentially fully integrated into the natural environment and no longer visible. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the systems and methods described in this application without departing from the scope or spirit of the invention. Other systems and methods will be apparent to those skilled in the art from their consideration of the specification and practice of the systems and methods disclosed in this document. The applicant intends that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.