The Sand and Gravel General Permit limits pollutants in discharges and requires monitoring of discharges to measure pollutant levels. The permit also requires the permittee to develop a monitoring plan and conduct representative sampling. The information below provides general guidance on what to include in the monitoring plan, goals and procedures for representative sampling, implementing the monitoring plan, reviewing the plan over time, and reporting to Ecology. The information here does not examine every aspect of permit requirements. The permittee is responsible for reading the full text of the permit and complying with all applicable permit requirements.
The permit requires that monitoring data be reported to Ecology once a quarter on or before the DMR due dates in the table below. Even if there were no discharges during the reporting period, the permittee must still file a report. Failure to report is a violation of permit conditions and can result in an enforcement action.
|Discharge Monitoring Period:||DMR Due Dates:|
|October, November, December||January 30|
|January, February, March||April 30|
|April, May, June||July 30|
|July, August, September||October 30|
Per the 2016 Sand & Gravel General Permit most inactive sites are not required to submit quarterly DMRs.
Discharge Monitoring Reports (DMRs) for the Sand and Gravel Permit are submitted quarterly, but the parameters might be monitored on a quarterly, monthly, or twice-monthly basis. In addition, the online DMR form doesn’t have a monthly No Discharge button. This can make it hard to figure out how to fill out the form without accidentally creating violations. Below is guidance for reporting when there was no discharge. Note that "No Discharge" means there was no discharge to sample during the entire reporting period. Your monitoring program must be flexible enough to take into account there may not be sufficient water available for sampling on any given day. Providing alternative sampling times, perhaps based on the occurrence of rainfall events onsite, is a good way to avoid this shortcoming in a plan. Sampling practices must be flexible enough to take advantage of storm events when they happen.
If you have a ground water discharge, you may be required to report either monthly or quarterly, depending on the activities that discharge to the ground.
If you have a surface water discharge, you need to enter at least two monitoring events for every month – because all surface water discharges require twice-monthly turbidity monitoring.
The monitoring plan must identify and provide basic information about each monitoring point. There must be sufficient monitoring points to provide representative sampling of all discharges onsite (see discussion on representative sampling below). Each monitoring point must be located on the site map and labeled. The label can only be five characters long and must be different for each monitoring point. This monitoring point label must be used on all monitoring information reported to Ecology. The label becomes the official identifier of the monitoring point. Examples of labels are G001 and S001.
The monitoring plan must provide the following information about each monitoring point:
The permittee is responsible for providing representative sampling of all discharges to ground and to surface water. Discharges to ground water include unlined ponds, infiltration trenches, and any place that water collects before draining into the ground. This does not mean that every place that water collects (e.g., every puddle) onsite must be sampled. It does mean that the reported monitoring values must be representative of the site. Surface water includes lakes, rivers, ponds, streams, inland waters, saltwaters, estuaries, wetlands, stormwater drainage systems, and all other surface waters and water courses within the jurisdiction of the state of Washington.
Representative sampling is not an average of values and it is not a mixing of samples from several locations and then measuring the value. It means the permittee must undertake a process to determine how many sampling sites are necessary to be representative of the site. Sampling is conducted at these representative sites.
To arrive at representative sampling, consider all the places that water typically collects. Take measurements at these locations and note what facility activities (NAICS codes) may impact the water. An analysis of the values and associated activities form the basis for determining the number of sample sites necessary for representative sampling. Consider:
The monitoring plan must include a description of how you determined what point or points to sample.
Depending on the activities at the site (NAICS codes) the permit may require monitoring for pH, total dissolved solids, and oil sheen.
pH Monitoring: The permittee is expected to conduct pH monitoring
onsite. Most often this will require acquisition of a pH meter. The pH meter
must be maintained and calibrated in accordance with operating instructions.
Total Dissolved Solids Monitoring (TDS): The permit requires that process water from concrete batch plants and asphalt batch plants be collected in lined ponds. Samples should not typically be taken directly from the lined pond. If possible, take a sample of the wastewater discharge after any additional treatment such as pH adjustment and just before it contacts ground.
Oil Sheen: The permit also requires a visual inspection for oil sheen. When water is present, there should be daily visual inspection in areas of the facility where employees and equipment are present. In portions of the facility where personnel and equipment are not active, visual inspections should be consistent with the frequency of personnel entering that area, but not less than once a month when water is present.
While representative sampling in discharges to ground emphasized finding representative sampling points, representative sampling in surface water discharges emphasizes identification of the most appropriate time to sample (see below). Monitoring parameters include pH, turbidity, total suspended solids, and oil sheen.
Parameters such as turbidity can vary considerably over the duration of a discharge and from one discharge event to another. Monitoring frequency can be increased (e.g., weekly, daily, continuous) to capture a complete picture of this variation or you can identify the values you are most interested in and schedule monitoring to increase the odds of measuring those values. Monitoring frequency in the Sand and Gravel General Permit relies in part on conducting sampling at the most appropriate time.
Turbidity and TSS: Sampling should be conducted when discharge turbidity and
suspended solids are likely to be greatest.
pH: Maximum and minimum values are of interest.
Oil Sheen: Visual examination.
Permit limits for pollutants in discharges are set to protect the environment. The permittee implements best management practices and treatment to assure that wastewater discharges will comply with permit limits. Monitoring is conducted to demonstrate how successful the BMPs and treatment are. In order for monitoring to make the demonstration, however, the samples must be taken when the potential for system failure is greatest. This is similar to proving that concrete meets the specified strength requirements. A representative cylinder of concrete is subjected to a cylinder compression strength test, compressed until it fails, demonstrating the strength of the concrete. The trick for monitoring is determining the best time to take a sample that will best test the effectiveness of BMPs and treatment.
Representative sampling for process water and mine dewatering water discharges should not present a difficult problem. These discharges can be easily anticipated, characteristics of discharge known, and sampling scheduled to capture a representative sample.
Discharges that result from stormwater, however, are less predictable and subject to significant variability both in quantity and quality of the discharge. Storm intensity, volume, and duration, as well as site conditions (e.g., saturation of soils, antecedent storms, increased activity, and unexpected erosion) can markedly influence the quantity and quality of stormwater. Therefore, it is recommended the permittee visually inspect the discharge during several major storm events (those 0.5 inches or more of rain in 24 hours). Pay attention to how the discharge quality (e.g., turbidity) varies over the duration of storms. Use these observations to determine the best time to obtain a representative sample and include the observations and sampling strategy in the site monitoring plan.
The permittee must follow accepted procedures for handling and shipping samples. Be aware of holding times; for example, pH of a sample must be measured within 15 minutes of taking the sample. If an accredited lab is used for analysis they can assist in this. They will typically provide the sampling containers and shipping materials. The permittee should make them aware of when they must submit their report to Ecology.
The permit requires a review of the monitoring plan on at least an annual basis. Conditions can change over time and sampling must remain representative. Periodic pH readings around the site, observations of site conditions and the visual quality of discharges are important. Even when there is no need to alter the monitoring plan, that decision and the date should be recorded in the monitoring plan.
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