Big Trouble For Dischargers?
The Impact of Pennsylvania's 2006 Integrated List
John C. Hall and William T. Hall
Hall & Associates

Originally published in the April/May/June 2006 issue of the Keystone Water Quality Manager. Download the original article here.

Pennsylvania's Integrated Water Quality Monitoring and Assessment Report (the "Integrated List"), characterizes water quality in all of the state's surface waters. The 2006 list was recently issued by the Pennsylvania Department of Environmental Protection (DEP) for public notice and comment. The documents that make up this assessment run well over a thousand pages and affect virtually every wastewater facility in the state. Of particular importance is Category 5 of the Integrated List. This category identifies all of the state waters not meeting water quality standards thereby requiring a total maximum daily load (TMDL) (i.e., more restrictive effluent limits). The Integrated List identifies 1,757 miles of stream that are impaired due to "nutrients" (not to be confused with low dissolved oxygen ("DO")) and 94 miles of stream that are impaired due to "excessive algal growth."

What is most intriguing about this extensive list of impaired segments is that DEP does not have water quality standards for "nutrients" or "excessive algal growth." Consequently, one must wonder how water quality standards can be exceeded for parameters without standards. The rationale for these listings may be found in DEP's 2006 Assessment and Listing Methodology for Integrated Water Quality Monitoring and Assessment Reporting ("Listing Methodology"). Therein DEP defines impairment due to nutrients and excessive algal growth as follows:

Presence of excessive quantities of Phosphorus and/or Nitrogen that under the proper conditions may result in dense algal or macrophyte growth and wide fluctuations in Dissolved Oxygen levels. Average daily DO may be relatively normal. Biological impairment may occur without Chapter 93 criteria violations. Appendix A, page 5; emphasis added.
Excessive Algal Growth
Large algal standing crops generally occurring due to high concentrations of nutrients. Appendix A, page 6; emphasis added.
These definitions should alarm all communities, especially those who discharge to a low flow stream. The definition for nutrient impairment goes far beyond any regulations legally adopted by DEP. It says, in effect, that designated uses need not be impaired for a stream to be listed as impaired. Under this definition, it does not matter whether "proper growing conditions," in fact, exist. Moreover, it appears that DEP presumes that biological impairment will occur simply because these nutrients are present. Interestingly, "dense algal or macrophyte growth" is not defined anywhere with respect to streams. There is also no definition provided for "large standing crops" in streams associated with excessive algal growth. As a result, it is unclear how DEP objectively arrived at its determination that about 1,800 stream miles are use-impaired due to nutrients.


Not withstanding the fact that there is no objective legal basis for listing stream segments as impaired due to nutrients as defined above, DEP has begun applying its new "nutrient impairment" concept in TMDLs for several drainage basins in Southeast Pennsylvania including the Neshaminy, Skippack, and Wissahickon Creeks. This represents a major change from DEP's historical approach to nutrient control. Prior to these actions, EPA and virtually every other state, including Pennsylvania, used DO impairment as the endpoint of concern to address nutrient impacts. If DO impairment was due to excessive algal growth, "growing season" nutrient limitations (e.g., June to September) were developed to control algae in conjunction with limits on CBOD and ammonia to the extent necessary to achieve compliance with DO standards. Typically, stringent total phosphorus (TP) limitations (less than 1 mg/L) did not result from this approach for streams. However, DEP began to implement a new policy resulting in dramatically more restrictive nutrient limits without undertaking rulemaking or formal scientific review of the basis for this approach. DEP's progression with respect to various TMDL decisions, as outlined below, shows how the more restrictive approach has been expanded and is now being used by DEP for regulating phosphorus.

Wissahickon Creek TMDL (2003)
EPA prepared and finalized this TMDL in October 2003. The TMDL evaluated algal impacts on minimum DO compliance and did not yield very restrictive seasonal limits on phosphorus (typically 1.4 - 2.3 mg/L monthly average). DEP submitted comments stating that the TMDL did not address "nuisance algae" but did not object to the final TMDL .

Neshaminy Creek TMDL (2003)
This TMDL was prepared by DEP in December 2003 to address phosphorus and sediment. The basis for the phosphorus limit was control of "nuisance algae." A 0.8 mg/L phosphorous limit was applied as a year round limit based on "best engineering judgment." DEP was uncertain whether a 0.8 mg/L limit was stringent enough to reduce plant growth. Consequently, DEP stated, "the TMDL will be reevaluated at a later date to determine whether more restrictive limits are needed."

Skippack Creek TMDL (2005)
This TMDL was prepared y EPA and finalized in January 2005 with close DEP oversight. The TMDL identifies "nuisance algae" as the endpoint and identifies 100 mg Chlorophyll-a/square meter ("Chl-a/m
2) as the threshold for "nuisance periphyton" conditions. The algal target is the amount of plants DEP will allow to grow on rocks in this stream. Based on an internal report prepared by Hunter Carrick (2005, Penn State University), it was asserted that an instream TP level of 0.24 mg/L was necessary to avoid periphyton concentrations in excess of 100 mg Chl-a/m2. DEP applied this value under 7Q10 flows and imposed year-round limits.

Draft Wissahickon Creek TMDL (2006)
In January 2005, DEP convinced EPA to reopen the 2003 Wissahickon Creek TMDL to address "nuisance algae" using the 100 mg Chl-a/m
2 periphyton and 0.24 mg/L TP endpoints. Over the course of a year, EPA and DEP worked to recalibrate the original WASP model to impose dramatically more restrictive phosphorus limits. The primary change to the model involves modification of the phosphorus half-saturation constant allegedly to control Cladophora, a filamentous green algae (this plant grows in abundance upstream of the treatment facilities). The draft Wissahickon TMDL is expected to be released for public comment in September 2006. It projects year round TP limits of 0.24 mg/L or less.

The listing procedure, as published, allows DEP to identify waters of the state as impaired for parameters with no accompanying water quality standards and where no actual impairment is demonstrated.
Draft Neshaminy Creek TMDL (2006)
On August 26, 2006, DEP issued a PA Bulletin notice requesting comments on draft revisions of the Neshaminy Creek TMDL. The draft was prepared by the Penn State Institutes of the Environment (University Park). Revised wasteload allocations, with a median TP limit of 0.23 mg/L, were developed based on a maximum instream phosphorus threshold of 0.227 mg/L to attain a 100 mg Chl-a/m
2 periphyton level. The basis for this TP standard is credited to Carrick and Godwin (2005). The restrictive wasteload allocation was used to set year round limits.

EPA Region III has also initiated a nutrient TMDL for Chester Creek, which will likely follow this "nuisance" algae format. The remaining stream segments identified as nutrient impaired on the 2006 Integrated List should expect similar treatment.

The manner in which these new highly restrictive water quality objectives have been internally developed and applied to TMDLs and permits is contrary to federal and state law. DEP needs to present to the public the technical basis for its new "nuisance" standard before such requirements are imposed via the TMDL program. The standards must be formally adopted and approved. 40 C.F.R. §131.2l.

Review of the justifications provided by EPA and DEP for development of these "nuisance" algae standards and stringent TMDL requirements for the draft Wissahickon and proposed Neshaminy TMDLs confirm that they contain scientific flaws and, in most respects, the justifications are directly refuted by the information used to set the requirements. Moreover, the approach cannot result in any discernible environmental benefit, as DEP's own data show that conditions upstream of treatment plants with phosphorus levels far below that targeted by DEP produce algal levels well above the alleged "nuisance" threshold. Thus, even eliminating the municipal loading cannot change this reality. The statewide cost of meeting a 0.2 mg/L limit would be expected to exceed a billion dollars. Typically, compliance with such restrictive limits would require construction of coagulation and filtration. Sludge generation would likely increase by 30-40%. Given the huge costs involved and the inadequate technical justification for imposing these limitations, DEP should reconsider this approach. Following are the basic scientific flaws we see in the "nuisance algae" standard and compliance strategy.


1. Proposed Phosphorus Endpoint Won't Control "Nuisance" Plant Growth

Assuming it is possible to effectively control the growth of nuisance periphyton (i.e.,
Cladophora), DEP's own research confirms that the nutrient levels (half-saturation constant) required to accomplish this are far lower than those used in the revised Wissahickon TMDL model (i.e., 0.015-0.087 mg/L versus 0.125 mg/L). With an instream phosphorus concentration targeted at 0.24 mg/L, Cladophora growth will be uninhibited. The fact that Cladophora grows upstream of point sources on the Wissahickon Creek where phosphorus levels average less than 0.05 mg/L confirm this fact.
If, however,
Cladophora growth is somehow inhibited at the levels chosen by DEP it is obvious that the chosen phosphorus standard (0.24 mg/L) will not generally limit periphyton growth to 100mg Chl-a/m2. Periphyton are assemblages of aquatic plants, with the different species in the assemblage competing for resources with one another. Some other benthic algae more adapted to the new stream conditions will take advantage of the niche previously occupied by Cladophora. Consequently, it is impossible for the phosphorus endpoint identified by DEP to meet the 100 mg Chl-a/m2 "nuisance" algae endpoint.

2. Nuisance Algae Endpoint is Questionable

A review of the Skippack TMDL indicates that the 100mg Chl-a/m
2 "nuisance" algae endpoint comes from the Carrick (2005) report, but that report did not derive the standard. Carrick said, "Based upon previous work, algal chlorophyll levels in streams that range from 100-150 mg/m2 are considered to be excessive or at nuisance levels (Welch et al. 1988). So, a reasonable target would be an average of 50-100 mg/m2 for periphyton in the stream." A similar quote is found in the Carrick and Godwin (2006) report for the Wissahickon Creek TMDL. Their citation is simply hearsay and is inadequate to justify a nuisance determination.
A review of Welch
et al. (1988) ('Welch") confirms that this "nuisance" level of periphyton was mischaracterized by Carrick. First, Welch reported that a nuisance biomass of filamentous periphytic algae may be represented by a level greater than 100-150 mg Chl-a/m2 based on laboratory experiments and a literature review. Thus, with one sentence in an internal DEP report, Carrick went from a summer average greater than 150mg Chl-a/m2 to a short-term average as low as 50mg Chl-a/m2 without providing any analysis to support why such a reading constitutes a "nuisance."
Second, Welch further noted that 100mg Chl-a/m
2 (or any other specific biomass) was not demonstrated to be a level that is expected to deplete stream oxygen resources through respiration and suppress benthic invertebrate communities. With respect to the definition of nutrient impairment provided by DEP in the Listing Methodology, it would appear that 100mg Chl-a/m2 cannot be considered a cause of DO impairment or biological impairment with regard to invertebrates. So what is the "nuisance"? Apparently, according to Welch, rocks with periphyton growth are "aesthetically displeasing" and "interfere with angler foot traffic." This is plainly not a sufficient basis to classify 1,800 miles of streams as impaired and impose state-of-the-art TP limitations.

3. Total Phosphorus Regulation is Ineffective

The TP endpoint selected for the Skippack Creek 2005 TMDL was 0.24 mg/L, the draft Wissahickon Creek 2006 TMDL identifies a TP endpoint of 0.248 mg/L, and the draft Neshaminy Creek 2006 TMDL identifies the TP threshold as 0.227 mg/L. The basis for these endpoints as described in the various Carrick reports as the predicted TP value that results in excessive periphyton growth (above 100 mg Chl-a/m
2). In both cases, the TP endpoints were determined using the regression model of Dodds et al. (2002) ("Dodds"). The Dodds regression analyses related periphyton chlorophyll-a to total nitrogen and TP. The regression analysis for phosphorus explains only 13% of the variance in the data (i.e., R2 = 0.13; 87% of the variance is unexplained). Such an R2 confirms that regulation of phosphorus is virtually useless for reducing periphyton growth. The Dodds regression analyses also ignored other, more Significant, factors such as light, scour, and grazing because the author believed these factors could not be controlled. This was directly at odds with Welch's conclusions.
The regression model presented by Dodds is based on an analysis of 200 observations from all over the world - not from Pennsylvania. The quality of the database is admitted to be unknown and widely varying conditions were combined. There is no reason to believe this regression has general applicability to streams in Pennsylvania. Moreover, Dodds describes this world dataset as consisting of annual mean values or seasonal means for at least two months of data. Consequently, the Dodds model predictions, if used at all, must be applied cautiously as annual mean or seasonal mean targets. This information confirms that DEP's imposition of the 0.2 mg/L standard at the
7Q10 flow is plainly inconsistent with the underlying science.
Given DEP's assumed universal applicability of the Dodds world database, it is obvious that the Dodds regression analysis will be applied to all Pennsylvania streams. DEP's latest position is the exact opposite of its determination in the Neshaminy Creek TMDL (2003) where DEP stated, "significant ecological differences in various areas of the country preclude broad applicability of transferred data." With such questionable applicability and reliability, the Dodd's regression model should be discarded, particularly as the site-specific periphyton data for the individual streams collected by DEP confirms that the regression is inapplicable.

4. Periphyton Target is Not Attainable

Data collected from the receiving streams during development of the various Southeastern Pennsylvania TMDLs confirm that the periphyton target of 100mg Chl-a/m2 cannot be achieved. Three stations on the Skippack Creek reported TP levels well below the 0.24 mg/L TP endpoint (0.059-0.105 mg/L) with periphyton chlorophyll-a levels well above the 100mg Chl-a/m
2 "nuisance" algae endpoint (126-417mg Chl-a/m2). Similarly, one station on a tributary to the Wissahickon Creek upstream of any point source dischargers had a TP level of 0.039 mg/L and a periphyton level of 276mg Chl-a/m2. Thus, even elimination of the Wissal1ickon discharge would not alter this occurrence. It is also worthy to note that Welch reported a periphyton level of 345mg Chl-a/m2 in response to a soluble reactive phosphorus concentration of 0.002 mg/L. DEP correspondence noted that 0.1 mg/L TP is a level of phosphorus that is routinely encountered in unimpacted areas, such as state parks. DEP's own biologists confirmed that light, not phosphorus, is the factor controlling whether or not high periphyton levels will be present (Everett 2002).
These data indicate that, if the 100mg Chl-a/m
2 "nuisance" algae endpoint is formally adopted by DEP, virtually all streams will be considered impaired. Moreover, as TP levels routinely exceed 0.02 mg/L, even in high quality streams, it is not possible to limit periphyton growth below 100mg Chl-a/m2 if other conditions favorable to plant growth exist (e.g., sufficient light).


Based on the information presented, it appears that the current direction the Pennsylvania TMDL program and strategy for nutrient reduction is headed needs to be reconsidered. The listing procedure, as published, allows DEP to identify waters of the state as impaired for parameters with no accompanying water quality standards and where no actual impairment is demonstrated.
The position that a periphyton concentration of 100mg Chl-a/m
2 constitutes a "nuisance" algae condition is not scientifically defensible. This is not a "nuisance" condition specific to Pennsylvania waters. It was attributed to researchers in Seattle, Washington (i.e., Welch), who reported that "others" suggested that such concentrations are aesthetically displeasing and interfere with foot travel by fishermen. If DEP's position is that exceeding 100mg Chl-a/m2 in a stream constitutes a "nuisance" under state law, supporting data must be presented and DEP must undertake appropriate rulemaking.

Finally, the determination that 0.2 mg/L of TP is an appropriate year-round endpoint to prevent a "nuisance" algae condition is clearly improper. Dodds, the source of the regression analysis, acknowledged that the best regression provided a very poor fit to the data. DEP's own detailed analysis confirmed that light, not nutrients, was the factor that controlled whether or where periphyton growth would occur. The real TP endpoint needed to limit periphyton growth, which is exceeded naturally even in high quality streams, is likely less than 0.02 mg/L. Establishing this endpoint would impose enormous regulatory costs on most municipalities throughout the state without any likelihood of environmental benefit.
The time for a broad-based response from the regulatory community is now. We believe that DEP should reconsider its current approach and conduct more research to thoroughly articulate phosphorus impacts on receiving streams based on updated and localized scientific findings. Further, we would recommend that DEP refrain from assigning phosphorus standards until they engage impacted sewer plants and other contributors in a formal regulatory review process.

EDITOR'S NOTE: At the time of publication EPA had withdrawn the Wissahickon Creek TMDL.
John Hall is the founder of Hall & Associates, a legal/regulatory consulting firm focusing on innovative solutions for compliance with Clean Water Act environmental mandates. He specialized in TMDL/WQBEL development, water quality standards adoption/modifications, and NPDES permitting/compliance issues. Mr. Hall represents municipalities and associations throughout the country, including numerous Pennsylvania communities. Recently, Hall & Associates formed the PA Periphyton Coalition, which focuses on DEP's nutrient regulation for stream dischargers. Mr. Hall has also served as special counsel to PMAA on wet weather flow compliance issues.

William Hall is a Principal of the firm Hall & Associates and has over twenty-five years of engineering and permitting experience in the areas of water quality, wastewater management, NPDES permitting, mathematical modeling, water quality standards, stormwater permitting, and industrial user permits. Prior to joining the firm, Mr. Hall was a Senior Project Manager with Environmental Resources Management, where he headed the stormwater permitting program. Mr. Hall is the author of several papers and articles on water pollution, environmental permitting, and toxicity issues. He is a member of the Pennsylvania Water Environment Association (formerly participating on the Industrial Waste and Government Affairs Committees) and the national Water Environment Federation, and is a frequent speaker on permitting issues.

Originally published in the April/May/June 2006 issue of the Keystone Water Quality Manager. Download the original article here.