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NPDES Stormwater Permitting: How it Affects You

By Doug Ruhlin | Environmental / Sustainability Consultant, Resource Management Associates

Let’s face it: Nobody likes to live or work around polluted surface water. Polluted stormwater runoff and process water discharge knows no boundaries, so it is the job of the U.S. Environmental Protection Agency’s National Pollutant Discharge Elimination System (NPDES) to limit the effects of waterborne industry pollutants to protect surface waters through the use of permits.


Agree with it or not, NPDES views concrete plants as “point sources” for water pollution. Permits require that plants maintain compliance by establishing a stormwater pollution prevention plan that incorporates best available management practices, so it’s important to understand the process and its strategies (see a related article at

Maintaining compliance is critical, since failure to do so can mean penalties including significant monetary fines – something that no precast producer can (or should have to) face in today’s challenging and competitive business market.

While many states allow the discharge of process water (see the sidebar “State Permits”), these discharges are viewed as:

    • Generally containing a much higher pollutant load than stormwater;
    • Much more capable of causing significant impact to the receiving water bodies; and
    • Preventable to a certain extent through recycling and source reduction activities at a concrete plant.

Therefore, these types of discharges are usually regulated much more tightly than other types of discharges, including holding them to very strict water quality standards. To achieve the pollutant levels required to meet these standards (known as effluent limitations) almost always would require elaborate and costly water treatment methods. As such, it is always in a precast concrete producer’s best interest to reduce the amount of process water or recycle it whenever possible for production, washing or coring activities.

Stormwater discharges under NPDES permits are usually regulated less stringently than process water discharges, primarily because nearly all industrial facilities discharge stormwater when it rains, which can be difficult to control and often cannot be prevented. Also, stormwater discharges in general are considered to have less impact on receiving water bodies due to lesser pollutant levels (in part due to dilution with stormwater).

Another key difference between stormwater and process water discharges is that exceedance of effluent limitations can lead to an enforceable violation with operational and monetary penalties (which can start at $27,500 per day in most locations), while exceedance of stormwater benchmarks usually requires a self-evaluation, enhancement of best management practices (BMPs) and perhaps reporting to the applicable regulatory agency.


It’s also important to note that whenever process water becomes mixed with stormwater, it becomes process water. It is then held to process water standards rather than the more relaxed stormwater standards. That is why it is imperative that every precast concrete producer do whatever possible to separate process water from stormwater discharges. This is usually done by restricting the process water generation and use area, using curbing or berms to deflect stormwater runoff away from process water areas, and covering process water areas such as coring areas.

A general rule of thumb for a precast concrete producer is this: Do not discharge process water – it carries too much unnecessary liability and cost. Of course, modern sustainability practices suggest that practices such as stormwater capture and harvesting (reuse) are excellent practices, and all precast producers should consider them. But from a regulatory perspective, you should still get an appropriate NPDES permit.


Precast concrete producers typically have stormwater discharges containing pollutants due to the presence of fine aggregate, unpaved yard and drive areas, and fine-grained concrete materials. These materials can generate the presence of solids in the stormwater discharge, which is usually indicated by the pollutants’ total suspended solids (TSS) and total dissolved solids (TDS). While many acknowledge that these materials may be natural in origin, unwanted or unacceptable levels of solids discharging into streams and other water bodies can cause significant negative impacts on those water bodies and the life within them. The potential presence of cement (although portland cement is rarely stored in a manner at a precast plant where it comes directly into contact with stormwater) and fine-grained concrete material can lead to elevated pH levels in stormwater, making stormwater more alkaline. Many regulators have included other pollutant parameters in the NPDES permits that precast producers may fall under for stormwater discharges, including chemical oxygen demand (COD) from the presence of chemicals such as admixtures and fuels at the precast plant; petroleum hydrocarbons from the presence of fuels, oils and lubricants; and iron from a variety of sources.

These pollutants are also present in process water discharges. Common limit levels are shown in Table 1. As can be seen, there is usually a significant difference between the pollutant levels that stormwater and process water are held to.

A review of the precast concrete producer stormwater data presented in Table 2 shows the following results:

    • The typical precast plant pollutants of pH and TSS show reasonably good results from 2005-present.
    • The pollutant parameter with the highest exceedances level was Fe (total dissolved iron). Review of a significant volume of stormwater data by the New Jersey Department of Environmental Protection – from many diverse industries – indicated that high exceedances rates were common, and that perhaps a benchmark level of 1.0 mg/L was inappropriately low. This parameter has been dropped.
    • Chemical oxygen demand (COD), TDSs and total petroleum hydrocarbon (TPH) levels were almost consistently below applicable benchmark levels, indicating that these pollutants have been successfully addressed by the precast concrete industry. TDSs and TPH were subsequently dropped from the current version of this permit, and it is anticipated that COD will be dropped on the next version of this NPDES permit.

Table 3 shows how the precast industry has met the challenge of implementing successful stormwater BMPs from 2005-present. If the mean has improved across this period, one could assume that the precast concrete producers involved have been successful in enhancing their BMPs in order to get better results – and produce cleaner stormwater runoff. Table 3 shows that all data has improved over time, indicating the following:

    • The use of stormwater monitoring data as a feedback loop to fine-tune BMPs has been successful over this period. Review of this data, and its use as a benchmark to fine-tune BMPs at precast plants, has resulted in mean TSS values consistently well below the applicable benchmark since 2008.
    • In general, the precast concrete producers are generating excellent (and compliant) stormwater results.


Stormwater monitoring, like NPDES permitting itself, may seem complicated and intimidating. It doesn’t have to be. If you’re not below your monitoring, seek qualified help.

Doug Ruhlin is an environmental/sustainability consultant with Resource Management Associates, which provides consulting services to the concrete and construction materials industries throughout the United States and internationally. View his website at or contact him at or (609) 693-8301.

Sidebar 1 – State Permits

In 45 out of 50 U.S. states, NPDES permits are issued by the state in which the precast concrete plant is located (not a corporate office or any other such location). The exceptions to this are Idaho, Alaska, New Mexico, Massachusetts and New Hampshire, along with Puerto Rico, the U.S. Virgin Islands and all U.S. Trust Territories where these permits are issued by EPA rather than the applicable state regulatory agency. States issuing their own permits under the NPDES program are referred to as “delegated,” and those few where EPA issues these permits are known as “non-delegated.”

NPDES permits are required for the discharge of any pollutant to any water of the United States or specific state. In the case of most precast producers, this means either stormwater discharges or process wastewater discharges. Most precast producers have stormwater discharges to surface waters either directly (such as to an adjacent waterway or wetland area) or indirectly (such as to a municipal storm sewer system). Many states also regulate discharges to groundwater, which would include retention basins for the capture of stormwater and process water. It is critical to know what your state regulates to ensure that you are in compliance with your applicable NPDES regulations.

Sidebar 2 – 9 Steps to Compliance

The following list is critical for all precast concrete producers:

  1. Don’t discharge process water. You don’t need to, it’s not a sustainable practice, and it carries too much liability under npdes permits.
  2. If needed, determine which permit is right for your precast operation, and get permit coverage. Without permit coverage, you have nothing. You may be in violation and subject to significant fines.
  3. Read your NPDES permit. Make sure you understand what it covers, what it does not cover, and what your obligations are under the permit.
  4. If you don’t think you need a permit for some particular reason, get it confirmed – preferably by the regulatory agency or an expert in the field. Don’t guess or presume.
  5. Do what you need to get into compliance, starting with the development and implementation of a stormwater pollution prevention plan (SWPPP).
  6. Determine what pollutants your NPDES requires you to monitor, and evaluate your facility and operation for the potential to discharge those pollutants. Probably it’s the pollutants discussed in this article.
  7. Determine and implement a program of BMPs to reduce or eliminate pollutant discharge.
  8. Review your monitoring data, and use it as it was intended – as a benchmark by which to gauge performance. If you are not getting results below your benchmark levels, review your facility and your bmps and make all necessary modifications.
  9. Finally, talk to other precast producers in your state. What kind of results are they getting? Can you present your data as a group, evaluating trends with the goal of higher benchmark levels or reduced monitoring requirements? Be proactive in this area!

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