Hydrology Surveys

The sand and gravel general permit requires the permittee to develop,  maintain, and comply with their erosion and sediment control plan  (ESCP) as a part of the Site Management Plan. The ESCP must contain  information on all the best management practices (BMPs) and structures  that control Type 2 storm water.

Portions of a site where mining has temporarily or permanently ceased;

Portions of a site with exposed soils, cleared in preparation for mining or other industrial activity.

If type 2 storm water enters areas associated with type 3 storm water, it becomes type 3 storm water.

Properly managed, type 2 storm water will typically not require  treatment. However, type 2 storm water cannot be allowed to discharge to  surface water if it exceeds the turbidity limit. Visual monitoring is  required and if turbidity is a problem, treatment may be required. The  information below provides general guidance on permit requirements and  useful information for permit compliance. It does not examine every  aspect of permit requirements identified under Special Condition S5.a.  Erosion and Sediment Control. The permittee is responsible for reading  the full text of the permit and complying with all applicable permit  requirements.

The ESCP must include information about all the best management  practices (BMPs) that are used to control type 2 storm water and prevent  erosion from adding sediment to the storm water. BMPs must include:

Stabilization practices help prevent erosion that contributes  sediment to storm water. Typical stabilization practices include seeding,  mulching, geotextiles, sod stabilization, vegetative buffer strips,  protection of trees, preservation of mature vegetation, and decreasing  slope angles or lengths.

Structural BMPs divert flows from exposed soils, store flows, or  otherwise limit runoff and the discharge of pollutants from exposed  areas of the site. Such practices may include silt fences, earth dikes,  drainage swales, sediment traps, check dams, subsurface drains, pipe  slope drains, level spreaders, storm drain inlet protection, rock outlet  protection, reinforced soil retaining systems, gabions, and sediment  basins.

At active mine sites and all asphalt batch and concrete batch plants,  you must conduct a visual inspection of all onsite erosion and sediment  control measures at least once every seven days, and within 24 hours  after any storm event of greater than 0.5 inches of rain per 24 hour  period. Keep a log of these visual inspections, recording the date and  pertinent observations (e.g., 12/7/99 – very heavy storm but no  significant turbidity in runoff).

For inactive mine sites, a Registered Professional Engineer or  equivalent (e.g., Certified Professional Erosion and Sediment Control  Specialist) must conduct an inspection every three years to determine if  the site is in compliance with permit conditions. Although inactive  mining sites are not subject to the same monitoring and reporting  requirements as active mine sites, BMPs must be in place and adequate to  comply with permit conditions. For example, any discharge to surface  water must comply with the turbidity limit.

Exposed soil is highly subject to erosion. Seeding the area to develop a vegetative cover can significantly reduce erosion.

Divert runoff from exposed soils. Dike or ditch the runoff, place a  berm around the exposed area, or convey drainage through pipes or  culverts. Runoff can be directed to a grass lined swale for  infiltration.

Slow down runoff to minimize its erosive capacity. Vegetative  buffers, slope management, check dams, and filter fabric fences are a  few of the ways that you can impact runoff velocity.

Use grass lined channels to convey water through the site. If grass  alone cannot control erosion, consider the use of rip rap. A pipe slope  drain may also be used to move water down a steep slope.

Barriers and temporary ponds may be used to trap sediment. Straw  bales, brush, and silt fences may be used as barriers to intercept sheet  flow or low level, low energy channel flow and reduce the sediment  load. Temporary ponds may also be used to trap sediment. These measures  do not typically provide adequate control of turbidity and should not  discharge directly to surface water.

Best Management Practices for Reclaiming Surface Mines in Washington  and Oregon. Available from the Washington Department of Natural  Resources, Division of Geology and Earth Resources, (360) 902-1450.  Although geared to mine reclamation, this document provides many useful  examples of site management that will minimize erosion and control  erosion.

Storm water Management Manual for the Puget Sound Basin – Volume II  Erosion and Sediment Control. This is a very good source of information  on preventing erosion and controlling sediment in runoff. There are many  useful management practices included in this volume. This document will  be replaced by an updated version that will likely be available by July  of 2000. The updated version will be a statewide manual: Storm water  Management in Washington State – Volume II Construction Storm water  Pollution Prevention. Although titled construction storm water, the  contents are highly applicable to erosion and sediment control  requirements of the sand and gravel general permit.

The plan is not intended to just sit on the shelf after completion.  The permit requires periodic review and updates to keep the plan  current. The plan should also be used during employee training. The plan  is intended to become a part of doing business at a site and to be a  living document.

For more information about Erosion and Sediment Control Plans (ESCP), contact Stratus Mapping today.

 A grading plan is prepared as part of the permitting process. It is  important that the runoff from each lot is directed to a stable outlet  rather than to an adjacent lot.

A grading plan (sometimes called a sediment and erosion control plan)  is required as part of the permitting process for builders. Stratus Mapping has many years of experience in creating accurate grading plans to meet the  requirements of local authorities.

Under the terms of the Georgia Sediment and Erosion Control Act of  1975, certification is required for anyone (including builders) who  engage in land disturbing activities, to prevent water runoff and  drainage from causing unintended consequences. Erosion and sediment  control are administered by local jurisdictions, each of which has  specific requirements for issuing the proper permits. It is important  that the runoff from any parcel of land is directed to a stable outlet  rather than to an adjacent lot. Hiring a licensed surveyor to create a  grading plan is the best way to ensure that the proper parameters are  met, and to ensure that your building project will not create  unacceptable runoff conditions.

A grading plan is designed to provide more suitable topography for  lots in order to control surface runoff, minimize soil erosion and  sedimentation, both during and after construction. Stratus Mapping will evaluate the  topography of the lot, and the resulting plan will define areas that  must not be disrupted by grading and filling. It will also show the  measures builders need to take in order to prevent damage to these  areas.

For more information about obtaining a grading plan for permitting, contact Stratus Mapping today.