1. Grading, erosion control practices, sediment control practices, and waterway crossings shall meet the design criteria set forth herein, and shall be adequate to prevent transportation of sediment from the site to the satisfaction of the Town of Dyer Plan Commission. Cut and fill slopes shall be no greater than 2:1, except as approved by the Town of Dyer Plan Commission to meet other community or environmental objectives.
2. Clearing and grading of natural resources, such as forests and wetlands, shall not be permitted, except when in compliance with all other chapters of this Subdivision Control Ordinance. Clearing techniques that retain natural vegetation and drainage patterns, as described herein, shall be used to the satisfaction of the Town of Dyer Plan Commission.
3. Clearing, except that necessary to establish sediment control devices, shall not begin until all sediment control devices have been installed and have been stabilized.
4. Erosion control requirements shall include the following:
a. Soil stabilization shall be completed within five (5) days of clearing or inactivity in construction;
b. If seeding or another vegetative erosion control method is used, it shall become established within two (2) weeks or the Town of Dyer Plan Commission may require the site to be reseeded or a nonvegetative option employed;
c. Special techniques that meet the design criteria outlined herein on steep slopes or in drainage ways shall be used to ensure stabilization;
d. Soil stockpiles must be stabilized or covered at the end of each workday;
e. The entire site must be stabilized, using a heavy mulch layer or another method that does not require germination to control erosion, at the close of the construction season;
f. Techniques shall be employed to prevent the blowing of dust or flow of sediment from the site;
g. Techniques that divert upland runoff past disturbed slopes shall be employed.
5. Sediment controls requirements shall include:
a. Settling Basins. A settlement basin is an impoundment with a controlled stormwater release structure for the purpose of detaining runoff to allow excessive sediment to settle. Settlement basins shall be required at the outlet of any disturbed areas with major grading that are larger than ten (10) acres. The minimum volume of a sediment basin shall be sixty-seven (67) cubic yards per acre for the total drainage area, measured below the top of principal spillway or riser. The cleanout volume shall be not less than one-quarter (1/4) nor more than one-third (1/3) of the total storage volume of a sediment basin. Maximum slopes shall be 2:1 (H:V) for excavated areas and for compacted embankments. Side slopes shall be 3:1 (H:V) or flatter, which will allow people and equipment to safely negotiate slopes or to enter the sediment basin for maintenance and repair purposes. The length to width ratio must be greater than 2:1 (L:W) for the principal flowpaths in order to maximize residence time of stormwater within the sediment basin. The principal outlet or spillway should be sized to adequately convey stormwater runoff from the two (2) year, twenty-four (24) hour storm.
b. Sediment Traps. A sediment trap is a small temporary pond that drains a disturbed area so that sediment can settle out. Sediment traps shall be required for any disturbed area which is greater than one (1) acre and less than five (5) acres. The minimum volume of a sediment trap shall be sixty-seven (67) cubic yards per acre for the total drainage area. The outlet structure shall consist of layers of aggregate, rock or riprap material. The cleanout volume shall be not less than one-quarter (1/4) nor more than one-third (1/3) of the total storage volume of a sediment basin. Maximum slopes shall be 2:1 (H:V) for excavated areas and for compacted embankments. Side slopes shall be 3:1 (H:V) or flatter, which will allow people and equipment to safely negotiate slopes or to enter the sediment basin for maintenance and repair purposes. The length to width ratio must be greater than 2:1 (L:W) for the principal flowpaths in order to maximize residence time of stormwater within the sediment basin. An emergency overflow weir should be provided at an elevation of at least one and one-half feet (1.5') below the top of embankment, with a minimum freeboard of one foot (1').
c. Silt Fences. Silt fencing shall be required on all disturbed areas and shall be constructed pursuant to the following standards:
(1) Install silt fence at level grade parallel to the contour of the land; extend ends upslope to allow water to pond behind fence; excavate a trench four inches (4") wide, eight inches (8") deep; install fence with posts on the down slope side; place twelve inches (12") of fabric in the trench, extending the bottom four inches (4") toward the upslope side; join silt fence sections by using a wrap joint; backfill trench with soil materials and compact; inspect at least weekly and after each storm event, repairing as needed and removing sediment deposits when they reach one-half (1/2) the fence height.
(2) The maximum drainage area to the silt fence shall be one-half (0.5) acre or less per one hundred feet (100') of fence. Silt fencing shall not be used in live or continuously flowing streams or channels and shall not be used in ditches or swales which drain areas greater than one (1) acre. Silt fences shall not be used in steep ditches or swales where the design flow is greater than two feet (2') per second.
(3) Silt fencing fabric shall be comprised of synthetic filter fabric manufactured from woven or nonwoven sheets of polypropylene, nylon or polyester. Typical properties for silt fencing fabric shall be as follows:
Tensile strength at 20% elongation: 50 pounds per linear inch
Burst strength: 180 psi
Trapezoidal tear strength: 50 pounds
Apparent opening size: 20 to 30 (US sieve size)
Flow rate: 0.30 gallons per minute per square foot
(4) The maximum length of silt fence between posts is eight feet (8'). Wood posts shall have a minimum dimension of two inches (2") x two inches (2") for hard woods (i.e. oak) and three inches (3") x three inches (3") for soft woods (i.e. pine). Typical post length shall be forty-eight inches (48"). There shall be a minimum of five (5) fasteners for each wood post.
(5) The maximum slope lengths for silt fence installations shall be as follows:
Land Slope Maximum Slope Length
Less than 2% 100 feet
From 2% to 5% 75 feet
From 5% to 10% 50 feet
From 10% to 20% 25 feet
More than 20% 15 feet
d. Protection for adjacent properties by the use of a vegetated buffer strip in combination with perimeter controls.
e. Installation and maintenance of drop inlet protection devices, utilizing either of the following techniques:
1. Silt Fence. Construct a six inch (6") dike on the down slope side to prevent bypass flow; dig a trench eight inches (8") deep and four inches (4") wide; space support posts evenly against the inlet perimeter a maximum of four feet (4') apart and drive them one and one-half feet (1.5') into the ground; use enough fabric from a single roll to eliminate joints and using lath and nails, fasten fabric to the posts; place twelve inches (12") of fabric in the trench, extending the bottom four inches (4") toward the upslope side; join silt fence sections by using a wrap joint; backfill the trench with soil materials and compact; cross brace the comers to prevent collapse of the structure; inspect at least weekly and after each storm event, and repair as needed, and remove accumulated sediments after every storm.
2. Placement of a pre-manufactured drop inlet protection device around the inlet perimeter, having at least the same design characteristics set forth in the preceding paragraph.
3. Block and Gravel. Place concrete blocks lengthwise on their sides in a single row around the perimeter of the inlet, so that the open ends face outward and not upward. Ends of adjacent blocks should abut. The height of the barrier can be varied by stacking combinations of blocks that are typically six (6) or eight (8) inches high. Place geotextile filter fabric over the outside vertical face of the concrete blocks. If more than one strip is necessary, overlap the strips by at least one foot (1'). Place clean stone against the geotextile filter fabric up to the top of the concrete blocks. Use one-half inch (1/2") to three-quarter inch (3/4") gravel.
5. Waterway and watercourse protection requirements shall include:
a. A temporary stream crossing installed and approved by the Town of Dyer Plan Commission if a wet watercourse will be crossed regularly during construction;
b. Stabilization of the watercourse channel before, during, and after any in-channel work;
c. All on-site storm water conveyance channels designed according to the criteria outlined herein;
d. Stabilization adequate to prevent erosion located at the outlets of all pipes and paved channels.
6. Construction site access requirements shall include:
a. A temporary site access road provided at all sites, unless the Town of Dyer Plan Commission determines that such temporary access road is not necessary. Such temporary site access road shall be constructed pursuant to the following standards:
Place six inches (6") of course aggregate (INDOT CA No. 2) over a stable subgrade; construct the road at least twelve feet (12') wide and fifty feet (50') long or the distance of the foundation; add stone as needed to maintain six inches (6") of clean depth.
b. Other measures required by the Town of Dyer Plan Commission in order to ensure that sediment is not tracked onto public streets by construction vehicles or washed into storm drains.
(Ord. No. 2004-13, § 1, 9-15-04)