treated u v stabilized composite hdpe woven fabric 90 which is prepared by alternately laminating a layer of ldpe 92 in between two layers of hdpe 91 the composite fabric 90 has three layers of hdpe which are made from hdpe granules added with uv stabilizing compound and which alternate with four ldpe layers signifying the word u2018 tetra u2019 of the product 39 s name the combined seven layers are laminated by extrusion coating into a single composite fabric 90 an inventive feature of the present invention is the use of the uv stabilized composite fabric 90 in construction of tetra vermi bed 100 uv stabilizing compound is added 3 5 by weight to the granules to prevent cracking of the composite fabric 90 caused due to exposure to sunlight tetra vermi bed 100 is constructed of a main panel 100 1 of said composite fabric 90 admeasuring 16 feet 9 inches by 4 feet 2 inches and of a twin side panel 100 2 100 3 of said composite fabric 90 admeasuring 12 feet 9 inches by 2 feet each side panel 100 2 100 3 is processed as explained below before it is joined with the main panel 100 1 tetra vermi bed 100 is firmly erected over laid ground 95 u2014 provided with a gradient of 6 inches over 12 feet u2014 by means.