To: PRB Committee
From: CDM Smith
Date: April 4, 2013
Subject: Technical Memorandum No.1: Evaluation Criteria for the Permeable Reactive Barrier (PRB) Pilot Project - Final
CDM Smith is pleased to present Technical Memorandum No. 1: Evaluation Criteria for the Permeable Reactive Barrier (PRB) Pilot Project. This is the first of six technical memorandums that will culminate with the recommendation of two PRB demonstration sites. Technical Memorandum No. 1 discusses the findings from Tasks 1.1.10, 1.1.11, and 1.1.12 of the contract scope of work and includes the following sections:
Section 1 – Summary of Existing PRB Knowledge Base
Section 2 – Environmental Permitting / Approval Requirements of PRBs
Section 3 – Potential Down-Gradient Impacts of PRBs
Section 4 – Summary
Section 5 – Summary of Comments from March 13, 2013 Project Meeting
Section 6 – Works Cited
1.0 Summary of Existing PRB Knowledge The following is a summary of existing PRB research that has been performed, specifically relating to the removal of nitrate in groundwater. The focus of this research includes the following aspects:
Available and proven PRB technologies implemented for the removal of nitrate
Performance metrics of operating PRBs
Reliability of PRBs to remove nitrate with scientific and regulatory certainty
Important design and siting considerations
Applicability of PRBs for treatment of nitrate in groundwater in Falmouth, Massachusetts 1.1 Existing PRB Systems for Removal of Nitrate The following section provides an overview on the types of PRBs that are currently identified as successful technologies for the removal of nitrate in groundwater. Table 1-1 and Table 1-2 include a comprehensive list of PRB studies that were conducted specifically to evaluate the effectiveness of nitrate removal, along with other design factors such as system longevity, hydrogeological and
PRB Committee April 4, 2013 Page 2 geologic impacts, environmental impacts, and multi-contaminant impacts on PRB performance. Table 1-1 includes full scale and pilot scale PRB installations and Table 1-2 provides a list of laboratory scale studies.
In total, CDM Smith has identified 17 pilot scale PRB installations designed to study the efficacy of nitrate removal in groundwater, amongst other design consideration, and 10 full scale installations, not all of which were solely designed to remove nitrate but all evaluated nitrate removal to some extent. In most instances, when the PRBs identified in Table 1-1 were designed to treat additional contaminants, those contaminants included chlorinated solvents and inorganics and are identified by the multi-PRB designation. These pilot and full scale PRBs are discussed further in Section 1.2.
1.1.1 Configurations There are several types and configurations of PRBs that currently exist and that have been found to be successful in the removal of nitrate in groundwater. Configurations of PRB installations can include any one of the following (The Interstate Technology & Regulatory Council, 2011):
Continuous PRB: Reactive media is spread across the width and vertical extent of the contaminant plume
Funnel-and-gate: Uses low permeability media to direct the groundwater to the treatment zone
In situ reactive vessels: Uses a funnel or trench to direct the groundwater flow into the reactive vessel
In most instances, PRBs are constructed vertically to intercept horizontal groundwater flow but horizontal PRBs can also be constructed with high permeability media to capture groundwater flowing vertically.
1.1.2 Reactive Media The type of PRB most commonly investigated for the removal efficacy of nitrate is with wood-based organic carbon reactive media. Multiple bench, pilot and full-scale installations have used this type of media as the substrate for biological reduction of nitrate. This media offers a number of advantages, including low cost, being readily available, and sometimes allowing the reuse of waste materials (e.g., mulch, compost). In some instances, PRBs using organic carbon reactive media may need to be rejuvenated after a certain number of years of operation, as was the case for the mixture of mushroom compost, woodchips and soybean oil at a PRB installed in McGregor, TX. This installation was primarily designed for perchlorate reduction but also assessed effectiveness of nitrate removal. Although the PRB was still performing satisfactorily after four years of operation, metrics were developed to plan for rejuvenation with emulsified vegetable oil due to slowing removal rates. Conversely, several organic carbon based reactive media PRBs have been operating for over an extended period of time and have not needed rejuvenation ((Kaszuba, et al., 2004), (Roberston, Vogan, & Lombardo, 2008), (Roberston, Blowes, Ptacek, & Cherry, 2000), (Robertson, Ptacek, & Brown, 2009)). The need to rejuvenate will also depend greatly on the existing conditions of the chosen sites, and can be assessed during the pilot testing.
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Table 1-1 Full Scale and Pilot Scale PRBs
Year Study Dimensions of Scale of Lifetime of PRB at Authors Title of Study/Report Location Reactive Media Initiated PRB (HxLxW) Implementation time of Report Treatability Study of Reactive polyelectrolyte- Materials to Remediate Ground 3 months (column impregnated porous Water Contaminated with Los Alamos Batch scale, tests) Conca et al. 2002 gravel, Apatite II layer, 12.5”x24.5”2” Radionuclides, Metals and Nitrates National Lab bench and pilot 100 days (2-D Aquifer layer of pecan shells, in a Four-Component Permeable Box Test) limestone gravel layer Reactive Barrier Nitrate Removal in NITREXTM Permeable Reactive Barriers Waquoit Bay, NITREXTM (Woodchips Bizzari, Lauren 2007 6.5’x66’x10’ Pilot scale 2 years Investigating Denitrification Using a Falmouth, MA and lime) 15 NO3 Tracer Western Groundwater Nitrate Removal Using Pilot scale (and Fahrner, Sabrina 2002 Australia (by Sawdust 6.5’x558’x5’ Over a year a Bioremediation Trench column tests) the coast) Nitrate Removal for On-Lot Sewage Hagerty, Paul; Bench and pilot Treatment Systems: The POINTTM unknown Lab Sawdust Unknown Unknown Taylor, James scale System Design, Installation, and Los Alamos 10% cottonseed meal, 10’&20’ Approximately one Kaszuba, John P., Performance of a Multi-layered National Lab, 65% pecan shells, and 2004 (depending on Full scale year (10 year design et al. Permeable Reactive Barrier, Los Mortandad 25% pea gravel (by the cell)x23’x17’ life) Alamos National Laboratory Canyon volume) W.D. Robertson, J.L. Nitrate Removal Rates in a 15-Year- Southern sand and wood particle Vogan, and P.S. Old Permeable Reactive Barrier 2008 Ontario (Long 2.5’x4’x2’ Pilot scale 15 years (sawdust) mixture Lombardo Treating Septic System Nitrate Point site) Waquoit Bay Effectiveness of Reactive Barriers and Childs NITREXTM (Woodchips 5’x40’x6’ Pilot scale and Vallino et al. for Reducing N-Loading to the 2008 3 years River and lime) 2.5’x65’x12’ bench scale Coastal Zone Falmouth, MA
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Table 1-1 (Cont’d) Full Scale and Pilot Scale PRBs
Year Study Dimensions of Scale of Lifetime of PRB at Authors Title of Study/Report Location Reactive Media Initiated PRB (HxLxW) Implementation time of Report The Effects of Seawater Intrusion on Microbial Nitrate and Sulfate Reduction within a NITREXTM Waquoit Bay NITREXTM (Woodchips Vincent, Angela 2006 5’x40’x6’ Pilot scale 1 year Permeable Reactive Barrier Falmouth, MA and lime) Designed to Mitigate Groundwater N-Pollution Schmidt, Casey; Efficacy of a denitrification wall to Alachua, 2012 Sand and sawdust 6’x181’x5.5’ Pilot scale 1.5 years Clark, Mark treat continuously high nitrate loads Florida High-Permeability Layers for Southern Robertson et al. Remediation of Ground Water; Go 2005 Wood particles 6.5’x4’x6’ Pilot scale 3 months Ontario Wide, Not Deep Wood decomposition after five Waquoit Bay years in anaerobic nitrate rich and Childs NITREXTM (Woodchips 5’x40’x6’ Feinberg, Daniel groundwaters: Implications for 2010 Pilot scale 5 years River and lime) 2.5’x65’x12’ lifetime of Nitrex™ Permeable Falmouth, MA Reactive Barriers Influence of NIRTEX barrier on groundwater flow paths, dissolved Waquoit Bay NITREXTM (Woodchips Moreau, Sabrina 2005 5’x40’x6’ Pilot scale Less than a year organic carbon and nitrate Falmouth, MA and lime) concentrations Upflow Reactors for Riparian Zone Southwestern Fine and Coarse wood 20 months and 4 Van Driel et al. 2006 3.5’x3.5’x3.5’ Pilot scale Denitrification Ontario particles months Hydraulic constraints on the performance of a groundwater Farm in New Shipper et al. 2004 Sawdust 10’x131’x10’ Pilot Scale 141 days denitrification wall for nitrate Zealand removal from shallow groundwater Denitrification of Agricultural Southern Fine and Coarse wood 26 months and 20 Van Driel et al. Drainage Using Wood-Based 2006 10’x131’x10’ Pilot scale Ontario particles months Reactors Several Wood−Based Filter for Nitrate NITREXTM (Woodchips Robertson et al. 2005 locations, unknown Full scale 3 to 5 years Removal in Septic Systems and lime) Ontario
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Table 1-1 (Cont’d) Full Scale and Pilot Scale PRBs
Year Study Dimensions of Scale of Lifetime of PRB at Authors Title of Study/Report Location Reactive Media Initiated PRB (HxLxW) Implementation time of Report Long-Term Performance of In Situ Several Wood mulch, sawdust, Robertson et al. Reactive Barriers for Nitrate 2000 locations, unknown Full scale 6 to 7 years leaf compost Remediation Ontario Geochemical and Hydrogeological Impacts of a Wood Particle Barrier Southwestern 3’x26’x8’ Robertson et al. 2007 Coarse wood particles Pilot scale Unknown Treating Nitrate and Perchlorate in Ontario Ground Water In Situ Denitrification of Septic- Robertson, W.; Southwestern System Nitrate Using Reactive 1995 Sawdust 5’x26’x26’ Pilot scale 1 year Cherry, J. Ontario Porous Media Barriers: Field Trials Nitrogen Removal from Landfill Robertson, W.; Leachate Using an Infiltration Bed Toronto, 1999 Sawdust 3.5’x42.5’x14’ Pilot scale 3 years Anderson, M. Coupled with a Denitrification Ontario Barrier Robertson, W.; In-Stream Bioreactor for Southwestern 2009 Woodchips 3.5’x65’x8’ Pilot scale 1.5 years Merkley, L. Agricultural Nitrate Treatment Ontario Rates of Nitrate and Perchlorate Removal In a 5-Year-Old Wood Southern Robertson et al. 2009 Wood particles 3.5’x42.5’x4’ Pilot scale Over 7 years Particle Reactor Treating Agriculture Ontario Drainage Schipper, Louis; Five Years of Nitrate Removal, Cambridge, Vojvodic-Vukovic, Denitrification and Carbon 2001 North Island, Sawdust 5’x115’x5’ Pilot scale 5 years Maja Dynamics in a Denitrification Wall New Zealand Performance evaluation of a (Height between Wilkin et al. carbon-based reactive barrier for 2006 Oklahoma Hay straw Pilot scale 7 years 8’-30’)x840’x4’ nitrate remediation (Height between sawdust and leaf mold Final Solar Ponds Plume Decision Golden, 20- RMRS 1999 with 10% zero-valent Full scale 2 years Document Colorado 30’)x850’x(Width iron between 2-3’)
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Table 1-1 (Cont’d) Full Scale and Pilot Scale PRBs
Year Study Dimensions of Scale of Lifetime of PRB at Authors Title of Study/Report Location Reactive Media Initiated PRB (HxLxW) Implementation time of Report Biogeochemical, mineralogical, and Oak Ridge hydrogeological characteristics of National Gu et al. 1997 zero-valent iron 30’x225’x2’ Full scale 5 years an Iron Reactive PRB for treatment Laboratory, of Uranium and Nitrate Tennessee Design and performance of a PRB for containment of Uranium, (Height between Morrison et al. Arsenic, Selenium, Vanadium, 1999 Monticello, UT zero-valent iron Full scale 3 years 11-13’)x103’x4’ Molybdenum, and Nitrate at Monticello, UT Massachusetts Final Ashumet Pond 2006 Military CH2M Hill Phosphorous Barrier Technical 2004 Reservation zero-valent iron 3’x300‘x40’ Full Scale 2 years Memorandum (MMR) on Cape Cod Length 600’ Geochemical Data Evaluation for Hill Air Force Battelle 2008 zero-valent iron (Height and Full Scale 3 years Hill AFB OU 12 PRB Base, UT width unknown) Building a Better Biowall: A 270’ in length Comparison of two design, Whiteman CH2M Hill 2004 Mulch (Height and Full Scale Unknown construction and operation AFB, MO Width unknown) strategies Many PRBs (Heights range from 1.6- NWIRP Selected mushroom Operation and Maintenance Manual 7’xLengths range ENSAFE 2002 McGregor, compost, wood chips, Full scale 4 years for Biowalls: McGregor, TX from 42- McGregor, TX soybean oil 800’xWidths range from 2.5- 4’)
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Table 1-2 Laboratory PRB Studies
Year Study Scale of Authors Title of Study Location Reactive Media Duration of Study Initiated Implementation Removal of added nitrate in the single, binary, and ternary systems of cotton burr Su, Chunming; compost, zero-valent iron, and sediment: Lab (Ada, 2007 Cotton burr compost and ZVI Batch scale Several days Puls, Robert Implications for groundwater nitrate Oklahoma) remediation using permeable reactive barriers Permeable Reactive Barrier Treatment Los Alamos Apatite® II (produced from fish Taylor et al. Technology for Remediation of Inorganic- 2002 Bench scale 285 days National Lab bones) and pecan shells Contaminated Groundwater Heterotrophic/autotrophic denitrification Rocca et al. (HAD) of drinking water: prospective use 2007 Lab (Italy) Cotton and ZVI Bench scale 170 days for permeable reactive barrier Effect of reactive media composition and Granular elemental sulfur and Moon, Hee. et al. co-contaminants on sulfur-based 2006 Lab (Korea) Bench scale 8 days limestone autotrophic denitrification Bench-Scaled Nano-Fe0 Permeable Reactive Hosseini et al. 2011 Lab Nano Zero-Valent Iron (NZVI) Bench scale Unknown Barrier for Nitrate Removal Development of a New Zero-Valent Iron ZanF(zeolite modified by Fe II, Lee et al. Zeolite Material to Reduce Nitrate without 2007 Lab (Korea) followed by borohydride Batch scale 470 days Ammonium Release reduction) A Fundamental Study on In-situ Method for Yamada et al. Removal of Nitrate-Nitrogen Contaminated 2006 Lab (Japan) SLAD (Sulfur/limestone) Bench scale 75 days Groundwater Mixture of Walnut Shell and Sand used to Lab (China Feng, Haigang et.al. 2011 Walnut shell Bench scale 92 days Nitrate removal in Groundwater University) Selection of organic substrates as potential reactive materials for use in a Batch and Bench Gibert, Oriol et al. 2008 Lab (U.K.) Softwood 130 days denitrification permeable reactive barrier scale (PRB) Removing Selenate from Groundwater with Lab (Fort Collins, Hunter, William 2006 Sand coated with soybean oil Bench scale 24 weeks a Vegetable Oil-Based Biobarrier Colorado)
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Table 1-2 (Cont’d) Laboratory PRB Studies
Year Study Scale of Authors Title of Study Location Reactive Media Duration of Study Initiated Implementation In-Situ Denitrification of Nitrate Rich Lab (Samples Israel, Sumaya Groundwater in Marydale, Northern Cape 2006 from Marydale, Sawdust Bench scale 28 days Town S. Africa) Removal of added nitrate in cotton burr Cotton burr compost, Canadian Su, Chunming; compost, mulch compost, and peat: Lab (Oklahoma, 2007 sphagnum peat, mulch Batch scale 10 days Puls, Robert Mechanisms and potential use for U.S.) compost groundwater nitrate remediation Use of Polymer Mats in Series for Sequential Reactive Barrier Remediation of Polymer mat with leached Patterson et al. 2002 Lab (Australia) Bench scale Less than a year Ammonium-Contaminated Groundwater: spearwood sand Laboratory Column Evaluation Nitrate removal rates in woodchip media of Lab (Waterloo, Robertson, W.D. 2010 Wood particles Bench scale 2 and 7 years varying age Canada) Multi-PRB ZVI with converter Stability of Multi-Permeable Reactive slag filings and biologically Lee et al. Barriers for Long Term Removal of Mixed 2009 Lab (Korea) reactive zone (waste tire Bench scale 1.3 years Contaminants rubber scrap with municipal sludge)
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Several types of inorganic reactive media including zero-valent iron (ZVI) and sulfur/limestone mixes have also been assessed as a means of nitrate reduction. Nitrate reduction using ZVI produces ammonia/ammonium, but the nitrate affects iron reactivity and therefore PRB longevity (The Interstate Technology & Regulatory Council, 2011). However, nitrate reduction using ZVI has proven to readily occur at the right conditions (Battelle, 1998).
1.1.3 Laboratory Studies Assessing the Removal of Nitrate with PRB Technology Many laboratory scale assessments have been performed to investigate various aspects of nitrate removal through different types of media and conditions and the applicability of the media in PRB technology. A summary of these studies can be found in Table 1-2.
Studies indicated that organic carbon based media removes nitrate more readily than with inorganic substrates such as ZVI (Su & Puls, 2007); however when media were paired to accomplish heterotrophic-autotrophic denitrification (HAD), greater nitrate removal rates were seen than when the organic substrate was the sole source of the nitrate reduction reaction (Rocca, Belgiorno, & Meric, 2006). Significant nitrate reduction was observed through the use of wood-based reactive media ((Gilbert, Pomierny, Rowe, & Kalin, 2008), (Israel, 2006), (Roberston W., 2010)) as well with the use of Apatite® II reactive media, which is a fishbone-based substrate (Taylor, Longmire, Counce, Chipera, Kaszuba, & Conca, 2002). Biofilm buildup and subsequent clogging of the test columns was found to be an issue in one study performed with walnut shell reactive media (Feng, Wang, & Jing, 2012).
Several laboratory studies have been performed in which autotrophic denitrification was utilized as the means of nitrate reduction. Studies performed with sulfur and limestone found that significant nitrate removal can be achieved, but the sulfur granule size plays an integral role in treatment efficacy, the smaller the granule size, the better the nitrate removal. Other important design factors include temperature and hydraulic residence time (HRT) (Moon, Chang, Nam, Choe, & Kim, 2006). One of the studies indicated that the presence of heavy metals in the test water inhibited the removal of nitrate (Yamada, Suemasa, Kaada, Nagaoka, & Nomura, 2006). ZVI has also been tested in the laboratory setting and seen successful results for the removal of nitrate, but long term laboratory tests have not been performed in which nitrate is the sole contaminant of concern ( (Lee, Lee, Rhee, & Park, 2007); (Hosseini, Ataie-Ashtiani, & Kholghi, 2011)).
1.2 Performance of Pilot and Full-Scale Operating PRBs The following section will discuss several of the pilot scale and full scale PRBs in operation that are identified in Table 1-1. The focus of these studies is to highlight the efficacy of the installation in removing nitrate on varying conditions and over prolonged periods of time.
1.2.1 Western Australia A study was performed at the Vasse Research Station, part of the Department of Agriculture, located near the coast in Western Australia. The Geographe Bay, the receiving water body for the surrounding agricultural area, has observed increased nutrient loading from local farming activities. The purpose of the study was to assess the effects of a sawdust-based PRB for nitrate remediation in the shallow
PRB Committee April 4, 2013 Page 10 aquifer. A 160-foot long trench-style PRB was installed approximately five feet wide by five feet deep. A significant reduction of nitrate (71%) was observed from groundwater upgradient of the trench to groundwater downgradient of the trench. Denitrification was the assumed method of nitrate removal due to favorable conditions for denitrifying bacteria such as pH, redox potential, and dissolved oxygen concentrations; however additional analysis to further assess this hypothesis was not performed at the time (Fahrner, 2002).
Mass balance calculations done on the organic media in the trench suggest that the quantity of sawdust applied to the trench would allow for an operational life of up to 20 years. This does not take into account the percentage saturation of the trench, microbial biomass build-up, nitrate concentration and nitrogen species and presence of the microbial community. Research suggests that microbial biomass build-up is not an issue with biologically reactive trenches amended with sawdust or wood chips; furthermore, clogging of the pore space was not observed during the field study (Fahrner, 2002).
1.2.2 Long Point Site, Southern Ontario One of the longest performing PRBs to be installed for the removal of nitrate is the Long Point Site, located in Southern Ontario. The pilot PRB was installed to treat a shallow groundwater plume with nitrate concentrations ranging from 30 mg/L to 100 mg/L. The source of the nitrate in the groundwater stems from a septic system built for a seasonal campground. The pilot scale PRB had been in operation for 15 years as of 2008 when a study was performed to assess its effectiveness in removing nitrate and to determine the nitrate removal capacity of the media (Roberston, Vogan, & Lombardo, 2008).
The 15-year-old media was extracted from the pilot installation by cores and placed into columns to determine reaction rates using dynamic flow modeling. Reaction rates from year one of operation were compared to year 15. The study found that the reaction rates in year 15 were approximately 50% of that found in year one (at 20° C to 22° C). Results from the study also indicated that the remaining media was still the primary source of organic carbon for denitrification. When the sawdust- based media was sieved out of the columns, nitrate removal dramatically dropped by approximately 80%. The study also confirmed estimates from previous studies (Roberston et al. 2000, VanDriel at al. 2006, Roberston & Merkley 2009) that also found that organic carbon is consumed by denitrification at a rate of approximately 1% of the initial carbon mass annually. Removal rates were found to vary exponentially with temperature with the highest removal rates observed in the summer months, which is consequently when the system was being used the most (Roberston, Vogan, & Lombardo, 2008).
1.2.3 Southern Ontario Nitrate removal rates were analyzed on a separate PRB installed in Southern Ontario. Removal rates were calculated on the pilot scale PRB between years one to eight. The PRB was installed to assess the treated groundwater from a farm field drainage tile, contaminated with both nitrate and perchlorate. The lateral flow PRB was designed with coarse wood chips in between two layers of sawdust. The woodchip layer acted as the main flow-through zone, with high permeability and the sawdust layers
PRB Committee April 4, 2013 Page 11 acted as sediment filters and provided additional denitrification capacity of the PRB. Continuous sampling occurred between year one to eight and detailed internal sampling with a multilevel piezometer was undertaken in year five (Robertson, Ptacek, & Brown, 2009).
Reaction rates for nitrate removal were found to remain consistent over the years of sampling; additionally, removal in the coarse wood layer is also similar to that found in the sawdust layers, indicating that higher permeability PRBs may be applicable in horizontal layer configuration as opposed to traditional vertical walls. Horizontal PRBs are typically installed in the saturated zone, especially when they are designed to use the anaerobic groundwater to reduce contaminants. These results also support previous studies which found wood particle barriers maintain stable nitrate treatment over a number of years, without the need for media replacement (Robertson et al. 2000, Schipper and Vojvodic-Vukovic 2001; Robertson et al. 2005a; Robertson et al. 2008). Assuming that nitrate attenuation stems entirely from denitrification, estimates from this study indicate that after year eight only 10% of the initial carbon mass in the reactor had been consumed. Results of sulfate reduction were also included in the detailed assessment conducted in year five. Sulfate reduction was observed in the PRB but to a much lesser degree when compared to nitrate removal. Additionally, in this study, the presence of sulfate did not appear to impact the efficacy of nitrate removal (Robertson, Ptacek, & Brown, 2009), which was also found in the pilot scale installation on Waquoit Bay (Vallino & Foreman, 2008).
1.2.4 Los Alamos National Lab, Mortandad Canyon Multibarrier PRBs are usually installed when there are a variety of contaminants present in the groundwater. One such PRB was tested at the pilot scale and subsequently built to full scale in 2003 for a design life of 10 years. The design of the PRB is funnel-and-gate with four cells for treatment of strontium-90, plutonium-238, 239, 240, americium-241, perchlorate, and nitrate. The nitrate treatment cells consist of Apatite (phosphate rock) followed by cottonseed meal, pecan shells, and pea gravel. Initial concentrations of nitrate of 8-12 mg/L were reduced below detection limits after 3 months of operation (0.01 mg/L). Initial microbial analyses suggest the presence of dissimilatory nitrate-reducing bacterial populations, along with production of acetate and propionate, and decreasing dissolved oxygen and pH (Kaszuba, et al., 2004).
1.2.5 Summary of Performance Metrics for Operating PRBs Performance metrics for PRBs treating nitrate include the parameters shown in Table 1-3:
Table 1-3 Performance Metrics of Operating PRBs Parameter Metric Observations Measure the degree to which groundwater is flowing through the Groundwater elevations Water levels PRB rather than around or under the PRB Percent nitrate removal Typically ranges between 70% and Nitrate concentrations (concentrations over distance) 100% removal using organic carbon
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Table 1-3 (Cont’d) Performance Metrics of Operating PRBs Parameter Metric Observations Elevated sulfate may shorten useful life of the PRB if organic substrate Sulfate concentrations Influent sulfate concentrations is used and causes production of ammonia. Maintain elevated dissolved or Biowall may need replenishment Dissolved organic carbon (DOC) total organic carbon (TOC) when DOC/TOC concentrations concentrations within the PRB decline Oxygen reduction potential Expect reductions in ORP during ORP or Eh (ORP) operation Low pH may require buffering pH pH agent to be added to allow denitrification to proceed Increase in ammonia concentrations may indicate that Ammonia may be produced when Ammonia concentrations conditions are not ideal for elevated sulfate is present denitrification Organic carbon consumed at a rate of approximately 1% of the initial Longevity % carbon mass lost carbon mass annually; longevity 20 to 30 years Fastest rate of removal occurs in Rate of nitrate removal first few years of operation then Efficiency of nitrate removal (concentration over time) levels out. Rates increase with higher temperatures
Increase in concentration of N2 gas Denitrification Concentration of N2 gas present indicates that denitrification is occurring
1.3 PRBs as an Approved Remediation Technology The USEPA recognizes PRBs as being an effective technology to remediate subsurface contamination at many types of sites. In the past, the regulatory approach has been to implement a more conventional remedy if the permeable barrier failed to meet performance criteria. The USEPA also identifies PRBs to be an excellent technology when compared to pump-and-treat systems with regard to cost savings (USEPA, 1998). PRBs continue to be highlighted in USEPA websites and documents. The Interstate Technology & Regulatory Council (ITRC), a state-led national coalition of personnel from all 50 state environmental regulatory agencies, three federal agencies, tribes, as well as public and industry stakeholders, identified that PRBs are also certified as acceptable means of remediation in almost all U.S. state environmental agencies in the most recent technical/regulatory guidance Permeable Reactive Barrier: Technology Update 2011 (The Interstate Technology & Regulatory Council, 2011). The Air Force Center for Engineering and the Environment has also prepared a technical protocol for the application of permeable mulch biowalls and bioreactors (AFCEE, 2008). In most instances, operational permits are not required for PRBs; however, permits may be required during construction, monitoring and closure ( (ITRC, 2011) (ITRC, 2005)). Contingency plans will be
PRB Committee April 4, 2013 Page 13 required in the event that a PRB fails to meet compliance criteria. Some examples contingency measures often accepted by regulators include (ITRC, 2011):
Extending the PRB to capture more of the plume if monitoring shows that the capture zone is inadequate;
Blocking the end(s) of the PRB with an impermeable barrier (slurry wall or sheet piling);
Modifying/amending the PRB if sufficient treatment is not being provided;
Installing a second PRB downgradient from or adjacent to the first one;
Pumping the PRB as an interceptor trench (a variation of the pump-and-treat measure);
Recirculating groundwater through the PRB or provide other active hydraulic control; and
Operating a pump-and-treat system if monitoring shows contaminant breakthrough or bypass for the PRB In a survey conducted by Gavaskar, et al. it was noted that regulators stated that actual contingency measures adopted would greatly depend on the mechanism of failure. Permitting requirements will be discussed in more detail in Section 3.0 (Gavaskar, et al., 2002). 1.4 Important Design Considerations Several studies have been performed to assess important design considerations of PRBs such as hydraulic constraints, hydrogeological and geochemical impacts, along with general siting considerations. Schipper et al. discovered that a denitrification wall that was installed at the pilot scale to treat farmland runoff from agricultural contamination was not performing as intended. Results from the study suggested that the majority of the groundwater flow was not intersecting the PRB due to reduction in the hydraulic conductivity compared to the surrounding soils. Groundwater appeared to be flowing around the PRB. The conclusion was made that PRB installations in coarse sandy soils may not be suitable for such reasons (Schipper, Gregory, Hadfield, Vojvodic-Vukovi, & Burgess, 2004). This discovery stresses the importance of understanding the hydrogeology surrounding the PRB installation and matching the PRB media to the adjacent aquifer conditions. Robertson et al. studied the geochemical and hydrogeological impacts of a PRB installation designed for the treatment of nitrate and perchlorate. Major conclusions from the study indicated that nitrate was highly attenuated in the first third of the four meter wide barrier. It was also postulated that carbon dioxide degassing likely occurred downgradient of the PRB which subsequently led to precipitation of calcite, siderite, and rhodochrosite as well as an increase in pH. It was also concluded, however, that plume composition four to six meters down-gradient of the PRB returned to upstream conditions, but with lower concentrations of nitrate, sulfate and calcium (Robertson, Ptocek, & Brown, 2007). This is an example that a sufficiently long reaction zone down-gradient of the PRB is needed to provide a buffer for secondary contaminants formed within the PRB to return to ambient conditions. This will be discussed more in Section 3. Table 1-4 summarizes important design and siting considerations of PRB installations for the treatment of nitrate in groundwater. Several of these are discussed in more detail in Section 1.5.
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Table 1-4 Design and Siting Considerations for Nitrate PRBs
Criteria Significance of Criteria Understand groundwater flow to properly intercept Hydrogeological plume Account for interactions with the geochemical Geochemical impacts composition of the aquifer Nitrate concentration Position PRB to target highest concentrations Important to understand if competing chemicals exist Competing contaminants in the aquifer Choose media that will best reduce nitrate Appropriate media type concentration at the chosen location Salt water intrusion may negatively impact system Proximity to tidal area longevity, increasing ammonia/ammonium and hydrogen sulfide production Total depth >45 feet to base of contamination is beyond practical depth of trenching or excavation Dimensions of plume using the one-pass method. May lead to consideration of injection methods1 Buildings or utility lines that cannot be breached may Infrastructure and land use leave gaps in the PRB. May lead to consideration of injection methods1 Will affect permeability, best case is homogeneous Soil types in aquifer soils1 Stratigraphy Best if PRB extends to confining layer of aquifer1 Important that PRB does not significantly affect the hydraulic conductivity of the aquifer. Best if K of
surrounding aquifer is < 1.0 ft/day. Depending on the Hydraulic conductivity (K) contaminant flux and reactivity of the media, higher velocities may be accommodated. Multiple sets of PRBs spaced along the axis of the plume could be used 1 to provide greater net residence time. pH of aquifer Best if pH is neutral1 Dissolved oxygen (DO) concentration Ideal DO concentration is < 4.0 mg/L1 Lower initial concentration is desirable so that ammonia/ammonium production is minimized, also Sulfate concentration useful life of PRB is lengthened due to less competition for substrate The thickness of the PRB is designed based on the required residence time of the contaminants PRB width and the groundwater flow velocity. Simple estimation of thickness is (V)*(t) where V is the groundwater flow velocity and t is the residence time.1 1. The Interstate Technology & Regulatory Council, 2011
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1.5 Applicability to Falmouth, Massachusetts This section discusses the performance of the Waquoit Bay and Childs River pilot scale PRBs, designed for nitrate removal, as well as the Ashumet Pond PRB, designed primarily for phosphorous removal and secondly for nitrate removal. Lessons learned from these studies are also addressed in this section so as to provide insight into a PRB installation in Falmouth.
1.5.1 PRBs installed on the Cape for Nitrogen Removal Years of research have been performed on the two pilot scale PRBs that are currently installed on the Cape for nitrate removal in Waquoit Bay and the Childs River. These NitrexTM PRB pilots have provided great insight into the operational efficacy of coastal PRBs, among other criteria such as: means of nitrate removal; effects of tidal inundation of saltwater; wood decomposition (Feinberg, 2010); influence of groundwater flow; and dissolved organic carbon.
The NitrexTM PRBs installations on the Cape have proved successful in reducing levels of nitrate in the groundwater (Vincent, 2006), (Moreau, 2005)), but have also highlighted several issues with coastal applications of PRBs. Most notably, the production of hydrogen sulfide (H2S) was observed from the reduction of sulfate induced by saltwater infiltration to the water table due to tidal inundation. The high sulfate levels is reported to have reduced the percentage of nitrate reduced via denitrification, yet nitrate reduction still proceeded ((Vallino & Foreman, 2008),
While saltwater intrusion has not been found to adversely affect the removal of nitrate, the observation has been made that the denser salt water can potentially drive the groundwater flow below the PRB, a condition called “undercutting.” The redirection of flow poses a problem with regard to inadequate treatment caused by tidal pumping. The same study recommended the use of an impervious cap in the case when the PRB must be installed close enough to tidal waters because surface inundation of saltwater could occur during high tide periods and/or coastal flooding. The impervious cap recommendation was offered as a viable approach for helping to minimize density driven downward circulation of seawater within the PRB (Vallino & Foreman, 2008).
The Vallino & Foreman (2008) report on the two nitrogen-removal PRBs also provided insight into other features of the nitrogen-contaminated groundwater flow that need to be considered during the planning and implementation of projects. First, the relatively dense network of monitoring points helped show that there is likely to be significant variation in plume concentrations over local, small scale distances (on the order of single-digit meters, for example). Second, the tidal range along the Falmouth coastline not only leads to inundation and the resulting infiltration of saltwater in the lowest-lying zone, but the tidal “forcing function” will also produce a pulsing action, leading to piston- type back-and-forth groundwater flow laterally. Third, the deeper plume at the Childs River PRB location provided a clear illustration of just how extensive the vertical extent of septic-system-caused contamination can be. This fits nicely with groundwater flow theory that says the closer the source to the groundwater divide, and thus the further upgradient toward the groundwater shed limit, the deeper the plume will be found in the flow field. All of these features point to the need for sufficient coverage of the pilot-demonstration monitoring points, and for local- and watershed-scale groundwater flow and plume modeling to help guide the monitoring program design.
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1.5.2 PRB for Phosphate Removal Extensive studies have been performed on the phosphorous plume from a wastewater treatment plant (WWTP) facility on the Massachusetts Military Reservation (MMR) in Cape Cod, Massachusetts. As part of the three-phase remedial strategy, a ZVI-based PRB was installed to intercept the plume where the highest concentrations of phosphorous enter the receiving water body, which is Ashumet Pond. The PRB was installed by excavating sediments from the pond, mixing the ZVI and placing the mixture back into the excavation. The barrier is 300 feet long, approximately three feet thick and extends approximately 40 feet offshore from the mean shoreline of Ashumet Pond. Continuous water quality assessments have indicated significant phosphorous reduction occurs inside of the PRB and highly reducing conditions (e.g., denitrifying, sulfate reducing, and methanogenic) have developed in the interior of the installation (Massachusetts Department of Environmental Protection, 2011).
Nitrate reduction was of secondary concern with regard to treatment of the plume, therefore there is less extensive data available on the performance of the PRB to remove nitrate. Additionally, the highest concentrations of nitrate and ammonium within the WWTP plume are located deeper in the aquifer and were not intercepted by the shallow PRB designed to treat the highest concentrations of phosphorous. Elevated nitrate concentrations observed beneath the barrier at 3.0 feet below pond bottom (bpb) were not observed at a depth of 0.5 feet bpb from samples taken at the same surface location. However, high nitrate concentrations were observed adjacent to the PRB at 3.0 feet bpb and similarly elevated nitrate concentrations were observed at 0.5 feet bpb from the same surface location. This contrast in nitrate concentrations within the PRB relative to concentrations outside the extent of the PRB indicates that nitrate is being removed, in many instances below detection limits (CH2M HILL, 2007).
Results from the study indicated that no plume-related contaminants were detected in the pond after two years of monitoring. After installation of the barrier, sediments along the shoreline turned red, which indicated that the iron in the ZVI mixture was being oxidized. The discoloring of the shoreline was an aesthetic concern and must be addressed when designing a coastal PRB with ZVI as the reactive media (Massachusetts Department of Environmental Protection, 2011). 2.0 Environmental Permitting/Approval Requirements of PRBs The purpose of this project is to evaluate the efficacy of PRBs to provide long-term, effective nitrogen plume attenuation. This study is conducted as a research and development (R&D) program to determine the role PRBs may have in helping Falmouth meet its required nitrogen load reductions to estuaries, pursuant to the Massachusetts Estuaries Program (MEP). Whereas the goal of PRBs is to reduce groundwater nitrogen loads to estuarine receiving waters, the siting of PRBs establishes a tension between one, locating the PRB near the estuary, and two, avoiding work in sensitive environmental areas to minimize environmental permitting requirements to install and maintain the PRB.
The suite of permits anticipated for this project without knowing the location of the one or more pilot PRB installations is discussed. This information however, is general in nature and a follow-up evaluation of site specific permitting requirements will be provided in Technical Memorandum No. 3 to present project specific permitting needs, once the final sites are known.
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Environmental permits are needed for work proposed in, or adjacent to, environmentally sensitive resources which are protected by federal, state or local statute. The purpose of the permitting process is to document that the proposed activity is consistent with the statute, via compliance with implementing regulations; and to document mitigation measures agreed to by the proponent that will minimize adverse effect by the project on the regulated resources. The resources in Falmouth subject to protection, and relevant to the pilot PRB project, include: freshwater and coastal wetland resources, habitats for protected wildlife and plants, navigable waterways, drinking water supplies and tributaries thereto, and cultural resources (historical and archaeological resources). Whereas the purpose the PRBs is to reduce nitrogen loads to estuaries, the most likely permits are those for work in wetlands or adjacent to wetlands and watercourses. PRBs are likely to be located in the state resource areas of Riverfront Area, Land Subject to Flooding or in buffer zones to wetlands and watercourses. Likely permits for the pilot PRB are listed below in Table 2-1.
Table 2-1 List of Potential Permits Required for Pilot PRB Installations
Issuing Agency Permit Program Permit Federal U.S. Army Corps of Engineers Section 404 of the Clean Water Act Army Corps Permit (USACE or Corps) (CWA) National Pollutant Discharge General Permit for Construction USEPA Elimination System (NPDES) Activities State Massachusetts Environmental Policy Massachusetts Environmental Policy MEPA Certificate Act Unit (MEPA Unit) Act Massachusetts Department of Environmental Protection Section 401 of the CWA Water Quality Certification (MassDEP) MassDEP M.G.L. Ch. 91 Waterways Program Ch. 91 License or Permit Massachusetts Division of Fisheries Massachusetts Endangered Species Conservation and Management and Wildlife Act Permit Massachusetts Historic Commission Section 106 & Chapter 254 Historic Preservation Act (MHC) Compliance Regional Development of Regional Impact Cape Cod Commission Cape Cod Commission Act Permit (DRI Permit) Municipal Falmouth Conservation Commission Wetlands Protection Act Order of Conditions (FCC) FCC Rivers Protection Act Order of Conditions FCC Falmouth Wetlands Bylaw Order of Conditions Falmouth Code ch. 240 Zoning - Falmouth Zoning Board of Appeals ZBA Special Permit - Article XXIX Earthmoving (ZBA) Earthmoving Regulations §240-150 - §240-157
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Although the list above seems daunting, many of the programs overlap in jurisdiction and require similar documentation to support permit applications. The permit process can be managed to determine the most efficient permitting sequence and to pursue related approvals simultaneously. The two basic strategies are to either secure generalized approvals first, i.e. MEPA review then proceed to local, state and federal permits; or alternatively first secure local permits to establish a local supportive constituency for the project, and then proceed with state and federal permits. Both are legitimate approaches and the final decision on the preferred approach is a case-by-case decision. Furthermore, many of the above programs have review, or permit, hierarchies based on threshold impacts such that projects causing fewer impacts can be reviewed quickly, while projects causing greater impacts require more rigorous and time consuming review.
The basic project purpose of the PRB is water quality and estuarine habitat improvement, thus it can be identified as a “self-mitigating project,” or in terms of the Massachusetts Wetlands Protection Act (the Act) as a project “which will improve the natural capacity of a resource area(s) to protect the interests” of the Act [310 CMR 10.53(4)].
Table 2-2 below presents the approximate time to prepare permit applications and typical review times, based on our experience with the issuing agencies. Please note, maximum statutory timeframes for the identified permits can exceed those presented in Table 2-2.
Table 2-2 Timeframes for Potential Permits Required for Pilot PRB Installations Time Required to Permit Review / Approval Time Prepare Application Federal Army Corps Permit (Category 2) 2 to 3 weeks 3 to 4 months General Permit for Construction Activities 2 to 3 weeks 3 to 4 months State MEPA Certificate 2 to 3 weeks 6 weeks Water Quality Certification 2 to 3 weeks 3 to 4 months Ch. 91 License or Permit 3 to 4 weeks + 6 months Conservation and Management Permit, i.e. Likely to follow “joint review” concurrent with Order of “take permit” Conditions Section 106 & Chapter 254 Compliance 1 to 2 weeks 4 to 6 weeks Regional DRI Permit 3 to 4 weeks + 4 months Municipal Order of Conditions 2 to 3 weeks + 2 months or less ZBA Special Permit 2 to 3 weeks + 2 months
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2.1 Permitting Approach The extent of permitting required for the PRB demonstration projects will be one of many criteria used to identify and prioritize potential project sites. It is our opinion that a site can be identified at which permitting is limited to an Order of Conditions, and Massachusetts Historic Commission review. We will seek to select a site and size the project to avoid other potential permits or approvals to the degree possible, but at the same time will not use permitting criteria as the only limiting factor. Following is a discussion of the permits identified above.
2.2 Description of Identified Permits Descriptions of the realm of possible environmental permits are provided below. This list will be reviewed and updated during review of pilot sites to determine site specific permit requirements.
2.2.1 Federal U.S. Army Corps of Engineers (USACE) - Section 404 and/or Section 10 Pursuant to Section 404 of the Clean Water Act (33 CFR 320-330), the USACE regulates the placement of dredged or fill material in “Waters of the United States”, which includes federally regulated wetlands and waterbodies. Work and structures that are located in, or that affect, navigable waters of the U.S., including work below the ordinary high water mark in non-tidal waters is also regulated by the USACE pursuant to Section 10 of the Rivers and Harbors Act. For Massachusetts the USACE issued a General Permit (GP) [Effective Date: January 21, 2010; Expiration Date: January 21, 2015], which allows certain activities to proceed without or with limited USACE review. There are three categories associated with the GP, Category 1, 2, and Individual Permit. Permit eligibility depends on the extent and nature of the impact, which cannot be determined without site-specific information.
Generally, if less than 5,000 square feet of a wetland or waterbody will be affected, and specific conditions of the GP are met, the project may qualify for a GP Category 1 approval. No formal application is required for a Category 1 project but submittal of a Category 1 Form to the Corps is required as part of the GP. If a project will alter 5,000 square feet to one acre of a wetland or waterbody, and specific conditions of the GP are met, the project may qualify as a GP Category 2 project, which requires submitting an application to the Corps and issuance of an approval per the GP. Projects affecting more than one acre of wetlands or waterbodies requires issuance of an Individual Permit, which has more rigorous review requirements and a longer review period. Note the Corps has discretionary authority to require an Individual Permit for projects affecting less than one acre of wetland/waterbodies if significant impacts are anticipated.
The USACE coordinates Category 2 and Individual Permit reviews with other federal resource agencies including the U.S. Fish and Wildlife Service and the USEPA. Additionally, applications must show compliance with Section 106 of the National Historic Preservation Act (NHPA) by including proof of project notification and coordination with the State Historic Preservation Officer (SHPO) [in Massachusetts the Massachusetts Historical Commission (MHC)], the Board of Underwater Archaeological Resources (BUAR), and Native American tribes, where applicable.
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Applicability: Constructing a PRB within a wetland would subject the project to review pursuant to Section 404 of the Clean Water Act and/or Section 10 of the Rivers and Harbors Act as fill material because the PRB reactive substrate would be placed in federal jurisdictional wetlands. Note, the Corps does not regulate any buffer zone extending landward from the wetland-upland boundary, thus it is likely that a PRB could be constructed adjacent to, but outside of, federal jurisdictional wetlands and therefore avoid an Army Corps Permit.
USEPA – Construction General Permit The USEPA regulates stormwater discharges associated with construction activities (such as clearing, grading, excavating, stockpiling, etc.) per the NPDES stormwater program. An NPDES Construction General Permit is required for construction sites that disturb one acre or more of land, i.e. expose erodible soil to precipitation and wind. A Stormwater Pollution Prevention Plan (SWPPP) is required describing construction best management practices (BMPs) that include erosion and sedimentation controls plus methods to treat and discharge of stormwater and/or uncontaminated groundwater dewatering. For a Construction General Permit, a Notice of Intent to Discharge (NOI) must be submitted to the USEPA-Region 1 and the SWPPP must be complete by the time the NOI is submitted. A project-specific permit is not generally issued by USEPA. The SWPPP is not reviewed by USEPA, but must be kept on site and available for review by an USEPA site inspector. Upon completion of construction, a Notice of Termination must be submitted to terminate the temporary discharge permit.
Applicability: Contractor typically obtains the NPDES Permit.
2.2.2 State Massachusetts Environmental Policy Act (MEPA) - MEPA Certificate The Massachusetts Environmental Policy Act (MEPA) requires the review and evaluation of certain large-scale projects to describe the environmental impact and requires that permit granting agencies identify feasible measures to mitigate potential environmental damage. The MEPA Regulations (301 CMR 11.00 et seq.) establish thresholds, a procedure, and time line for a two-tiered review process, which generally proceeds as follows: the project proponent submits an Environmental Notification Form (ENF) to the Secretary of Environmental Affairs (Secretary). A twenty-day public comment period follows during which time the Secretary receives comments from the public and agencies, and holds a site visit and consultation session. Within ten days of the close of the comment period, the Secretary issues a Certificate stating whether an Environmental Impact Report (EIR) is needed and what the scope of the EIR should include, if required. If no EIR is needed the state permitting agencies can issue the required permits and the project can go forward. Please note, MEPA approval is not required before an Order of Conditions is issued by a local Conservation Commission. If an EIR is required, it is prepared by the proponent and submitted to the Secretary. The EIR is reviewed and commented on at both Draft and Final stages by the public, state agencies, the Secretary, and the MEPA Unit. After completion of review, the Secretary issues a Certificate approving the project.
Applicability: The pilot PRB project is not a large or complex project that by itself would trigger MEPA review. However, the location of the PRB may trigger MEPA review, such as: 1) siting the PRB within
PRB Committee April 4, 2013 Page 21 the Waquoit Bay Area of Critical Environmental Concern [301 CMR 11.03(11)], or 2) altering two or more acres of protected habitat that results in a “take” of a protected species [301 CMR 11.03(2)(b)]. It is likely that a PRB pilot project can be sited and sized to avoid MEPA review.
MassDEP – Section 401 Water Quality Certification Per Section 401 of the Clean Water Act, states must certify that water quality criteria will be met before federal permits are issued for projects that will discharge dredged or fill material into waters of the U.S. ( i.e. federal jurisdictional wetlands or waterways). In Massachusetts the DEP administers the Section 401 Water Quality Certification program via state regulation 314 CMR 9.00 et seq., which establishes the protocols to review and determine that state water quality criteria are met. Section 401 Certification is triggered when a federal permit, e.g. an Army Corps Permit, is needed for filling wetlands and/or waterways. Certification is not required for projects covered by the USACE GP Category 1. Currently, there are two categories of water quality certifications in Massachusetts:
1. Generic Section 401 Water Quality Certification – Those projects that meet certain conditions, (including but not limited to: receipt of an Order of Conditions; filling of less than 5,000 square feet of wetland or waterbody; and/or dredging less than 100 cubic feet, etc.), do not require separate certification because the issuance of an Order of Conditions by the local Conservation Commission serves as the Water Quality Certification in such cases.
2. Individual Section 401 Water Quality Certification – An individual certification is required if, among other criteria, more than 5,000 square feet of wetlands or waterbodies are filled, or if work is proposed in an Outstanding Resource Water (e.g. a drinking water supply reservoir, venal pool, or other water bodies so designated by the MassDEP).
Applicability: If the pilot PRB project will require an Army Corps Permit GP Category 2 or Individual Permit, then a Water Quality Certification will be required. We anticipate that a pilot project can be located landward of a federal jurisdictional wetland or waterway, and thus avoid the need for a Section 401 Water Quality Certification.
MassDEP - Chapter 91 Waterways License or Permit The Massachusetts Waterways Program (MGL Chapter 91) and its regulations require a Chapter 91 waterways license or permit for any structures or fill located in, under, or over flowed tidelands, filled tidelands, all submerged lands lying below the high water mark of a Great Pond and certain non-tidal rivers, and streams located throughout the Commonwealth.
Applicability: It is unlikely that a pilot PRB will be located below the mean high water line; however, one could be located within “filled tidelands.” The Ch. 91 Regulations are silent regarding monitoring wells. The general purpose of Ch. 91 is to protect the navigability of waterways. Therefore should PRB monitoring wells need to be located in Ch. 91 jurisdictional waterways, we would consult with MassDEP via a Request for Determination to confirm the need, or lack thereof, for a Ch. 91 License or Permit.
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Massachusetts Division of Fisheries & Wildlife – Conservation & Management Permit The Massachusetts Endangered Species Act (MESA) prohibits the "take" of any rare plant or animal species listed as Endangered, Threatened, or of Special Concern by the Massachusetts Division of Fisheries & Wildlife (MDFW). "Take" is defined in MESA as to harass, harm, pursue, hunt, shoot, hound, kill, trap, capture, collect, process, disrupt the nesting, breeding, feeding or migratory activity of an animal or to collect, pick, kill, transplant, cut or process a plant. Areas of Falmouth are mapped as estimated habitats for state listed species. When projects involve MESA review and also require approval pursuant to the Massachusetts Wetlands Protection Act, MESA review can be initiated by submitting the NOI (wetland permit application) to MDFW. Through this “joint review,” the MDFW will determine whether a Conservation and Management Permit, or “take permit” is needed.
Applicability: We anticipate that a pilot project can be located to avoid MESA review.
Massachusetts Historical Commission - Historic Preservation Act, Section 106 and Chapter 254 Compliance The Massachusetts Historical Commission (MHC) is the state agency which functions as the State Historic Preservation Officer (SHPO) in Massachusetts and identifies, evaluates, and protects the state’s significant cultural resources per Section 106 of the National Historic Preservation Act (NHPA). Any new construction projects or renovations to existing buildings or structures that require state funds, licenses, or permits are subject to the review requirements of the M.G.L. Chapter 9, Sections 26-27c, as amended by Chapter 254 of the Acts of 1988 (950 CMR 71.00), and MEPA. The state regulations set up a review process that mirrors the federal “Section 106” regulations to identify historic properties, assess effect, and consult interested parties to avoid, minimize, or mitigate any adverse effects. NHPA defines historic property as any prehistoric or historic district, site, building, structure, or object included in, or eligible for inclusion in, the National Register of Historic Places (NRHP).
Compliance with Section 106 and/or M.G.L Chapter 9, Sections 26-27c, as amended by Chapter 254 if the Acts of 1988 (950 CMR 71.00) is also generally required as part of the USACE permitting review process.
Applicability: We do not anticipate adverse impacts to any historic structures and buildings, or disturbing a known archaeological site. Regarding archaeological resources, the MHC uses a geographic based sensitivity model to rate undocumented but potential archaeological sites as high, moderate of low sensitivity. Sites on slopes or uplands adjacent to rivers, lakes, ponds and the ocean are generally considered to be more sensitive to the presence or archaeological artifacts than other locations. Past disturbance history is considered also to determine sensitivity.
Early consultation with the MHC is advised during the planning process to determine if any significant cultural resources could be affected by the pilot project. A Project Notification Form (PNF) is submitted to initiate MHC review and should be submitted during the preliminary planning stage. The PNF should include: a detailed narrative description of the proposed project; a description of the existing conditions and the nature of any past development of disturbances on the project site, if any;
PRB Committee April 4, 2013 Page 23 a list of all the federal and state funds, licenses, and permits required for the entire project; photographs of existing areas to be disturbed; and a USGS project location map and proposed site plan.
2.2.3 Regional Cape Cod Commission – Development of Regional Impact (Cape Cod Commission Act) The purpose of the Cape Cod Commission is to conserve and preserve natural undeveloped areas, wildlife, flora and habitats for endangered species; preserve coastal resources including aquaculture; protect groundwater, surface water and ocean water quality, as well as the other natural resources of Cape Cod; balance economic growth; coordinate the provision of adequate capital facilities with the achievement of other goals; develop an adequate supply of fair affordable housing; and to preserve historical, cultural, archaeological, architectural, and recreational values on Cape Cod. Applications for development projects are also subject to review by the Cape Cod Commission if the development meets certain thresholds defined in Section 3 of their regulations.
Applicability: Site alterations of two or more acres are presumed to require review as a Development Regional Impact (DRI), unless the alteration is conducted in conjunction with a municipal project. The pilot project is unlikely to be determined as a DRI, because 1) it is unlikely to meet or exceed the two acre disturbance, and 2) it is a municipal project.
2.2.4 Municipal Falmouth Conservation Commission - Order of Conditions (Massachusetts Wetlands Protection Act) The Massachusetts Wetlands Protection Act (MWPA) regulates alteration of state defined wetland resource areas and the Massachusetts Wetlands Protection Regulations (310 CMR 10.00 et seq.) identify wetland resource areas subject to protection and present the regulations for work in these wetland resource areas. Although a state law, the MWPA is administered at the local level by the municipal Conservation Commission.
A Notice of Intent (NOI) is the application prepared and submitted to the Falmouth Conservation Commission for activities within areas subject to protection under the MWPA. The MWPA Regulations also identify a 100-foot buffer zone to specific wetland resource areas and work within buffer zones requires approval from the Conservation Commission.
Applicability: Whereas the purpose of the PRB is to improve groundwater quality, especially nitrogen removal in this application, it is likely work will occur in the 100-year flood plain, a state regulated wetland resource area, or within the 100-foot buffer zone to wetlands or watercourses.
Falmouth Conservation Commission - Order of Conditions (Rivers Protection Act) The Rivers Protection Act protects perennial rivers, streams, brooks, etc., in the Commonwealth and is enacted through Section 10.58 of the Massachusetts Wetlands Protection Regulations. It establishes a 200-foot wide Riverfront Area that extends horizontally on both sides of perennial waterways. Because the Rivers Protection Act is administered through the Wetlands Protection Regulations, the
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NOI submitted to the Falmouth Conservation Commission pursuant to the MWPA will concomitantly serve as the Rivers Protection Act permit application.
Applicability: Similar to the MWPA approval for work within a Riverfront Area, i.e. within 200 feet of a perennial river or stream, will require an Order of Conditions from the Falmouth Conservation.
Falmouth Conservation Commission – Order of Conditions (Falmouth Wetlands Bylaw) The Town of Falmouth established a Wetlands Bylaw to protect wetlands, related water resources, and adjoining land areas in the Town. The Wetlands Bylaw is administered by the Falmouth Conservation Commission. Areas subject to the jurisdiction of the MWPA plus additional “local” jurisdictional wetlands, e.g. Lands and Water within Black Beach/Great Sippewisset Marsh District of Critical Planning Concern, and Lands and Water within the Waquoit Bay ACEC, are regulated by the bylaw.
Approval for work subject to the bylaw is met by filing of a Notice of Intent pursuant to both the MWPA and the Falmouth Wetlands Bylaw.
Applicability: Similar to that of the MWPA plus work within local jurisdictional areas noted above.
Falmouth ZBA – Special Permit for Earthmoving (Falmouth Code ch. 240 Zoning -Article XXIX Earthmoving) A Special Permit is required from the ZBA for excavating or moving 1,000 cubic yards or more of earth within any three-year period. This is not applicable to lands subject to Falmouth wetland and floodplain regulations.
Applicability: The pilot PRB project may require excavating 1,000 or more cubic yards of earth, which would require ZBA approval.
3.0 Potential Down-Gradient Impacts of PRBs This section identifies and addresses the issues and concerns related to potential environmental impacts down-gradient of a PRB, both intentional and unintentional. This is accomplished in part by outlining important hydraulic and geochemical modeling and design considerations at the pilot and full scale phases.
3.1 Important Design Challenges To address the potential for down-gradient as well as up-gradient impacts , the PRB locations should be chosen and their design guided by the objectives of the pilot-demonstration testing, which will differ to some degree from the objectives of a full-scale implementation design. Thus, although the pilot-test locations and specific installation at each location will be designed to achieve a successful demonstration, the hydrogeological and geochemical aspects of the pilot-testing should include at least some demonstration of the challenges facing full-scale implementation, and the steps that need to be taken to achieve success. In addition, the pilot-test installations should be situated and designed to fit within a subsequent full-scale installation, to the extent feasible.
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Within this overall approach, the pilot-testing objectives should address each one of the five challenges, enumerated in the scope work as follows:
The need to match the transmissivity and the hydraulic conductivity of the pilot PRB to the hydraulic properties of the aquifer to help insure the required residence time, and to limit groundwater seepage around the PRB.
Longevity of the PRB media in terms of a carbon source to convert nitrate to nitrogen gas, and potential need for carbon addition.
Proper grading during construction to minimize changes in groundwater flow quantities and directions.
Water quality differences between groundwater at the center of the PRB and its perimeter of emplaced materials, and related boundary effects.
Tidal impacts of seawater on the PRBs and potential reduction in the rate of nitrate removal.
Additional challenges CDM Smith foresees to be of significance to the Town of Falmouth include:
Construction location to allow for instrumentation to measure both piezometric heads and groundwater heads.
Lack of existing/prior groundwater monitoring in “necks” and estuary/pond areas. Related to the lack of existing/prior monitoring data in key areas is the partial characterization of septic system- caused nitrogen plumes and/or the uncertain plume growth patterns, even in regard to some of the most intensively-studied groundwater contamination problems in the nation. This was demonstrated by the Waquoit Bay and Childs River NitrexTM PRB installations, as described above, because the monitoring data showed significant variation spatially and temporally in concentrations, as well as what was reported as an unanticipated deeper plume at one of those PRB locations.
Need for coordination and taking-advantage-of-synergies with anticipated efforts that will reportedly be conducted by the USGS and perhaps other entities; and, therefore, need to communicate with such entities and/or anticipate the locations and technical challenges they will be focusing on, as well as the constraints imposed that are related to the funding, timing, and duration of such efforts.
Need to set the objectives and metrics for short-term pilot/demonstration phase monitoring differently than for long-term full-scale implementation purposes. The detailed/dense monitoring conducted during the pilot-testing project is required for proof-of-concept, whereas compliance monitoring with a significantly less dense network and lower frequency of sampling will suffice for the implementation phase. It is therefore very important to highlight the significant differences in objectives and metrics from the very start of the pilot/demonstration phase efforts, so that the
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regulatory agencies and potentially-impacted stakeholders understand the contrasts and approve the approaches recommended during each phase.
Desire to locate one of the PRBs in the West Falmouth Harbor watershed, where the relatively significant depth of the water table and the nitrogen plume emanating from the infiltration basin area at the existing wastewater treatment plant must be addressed.
3.2 Guiding Principles for Proper Design In addressing each challenge, the pilot-testing should be based on the following guiding principles related to the hydrogeological and geochemical aspects of avoiding negative down-gradient impacts while maximizing positive nutrient reductions.
3.2.1 Depth of Plume Locations that are conducive to shallow PRB installation will be selected for pilot-testing, as opposed to sites with a significant depth to groundwater. In addition, the selected locations will be where the septic system caused nitrogen plumes are also shallow enough to the extent possible to avoid having to install the PRBs using methods besides trench excavation and backfilling. Although techniques that involve injection of the carbon source medium are feasible, this approach is not recommended initially due to lesser cost options being available.
3.2.2 Locating PRB Away from Saline Water and Wetlands Location-selection will consider use of a 100-ft buffer from saline and fresh surface water features, and from mapped wetland edges, in part to help avoid downgradient impacts due to geochemically- induced changes in groundwater quality. The 100-ft buffer approach will help avoid saltwater inundation potential, as will the identification of very low-lying land areas along the coastline which are subject to flooding during high tides and coastal storm surges and wave run-up. The inundation of saltwater and subsequent infiltration to the water table led to observed geochemical changes during the PRB demonstration project as reported by Vallino and Foreman (2008), some of which could negatively impact PRB performance. Specifically, the presence of sulfate has been found to adversely impact the longevity of the PRB due to sulfate reduction and subsequent usage of the organic carbon source.
Desktop calculations are sufficient at this stage for such purposes as assuring that a 100-ft buffer is adequately large to avoid deleterious impacts, such as water quality violations or influences from saline water, while not placing each PRB too far inland in terms of the depth required to intercept the plume. Focused numerical modeling, complemented by desktop check-calculations, will be conducted during the next stage of this pilot test planning project. For the current project stage, calculations will be conducted for estimating groundwater velocity and for describing potential deleterious geochemical changes over time – this is intended to result in confirmation as to whether the 100-ft buffer is needed to protect against significant impacts due to the pilot testing, or for setting a larger (or smaller) buffer distance, if needed.
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Secondary, down-gradient water quality impacts should be avoided through the consideration of pre- installation data collection and evaluation of field and lab testing results that are focused on characterizing the potential for geochemical changes, and the potential for the changes to trigger unwanted impacts even past the buffer limit. As stated by the ITRC (The Interstate Technology & Regulatory Council, 2011):
In many cases, providing a downgradient redox recovery zone is sufficient [to address secondary water quality issues]. This is readily accomplished at many large DOD/DOE facilities but may be more difficult to incorporate at small industrial or commercial sites.
Thus, while this document does not state the size of this redox recovery zone, the authors imply that site-specific data collection and evaluation would help in determining feasibility and acceptability, while also providing the basis for conducting predictive modeling for refining the estimate of required buffer-extent.
At present, field sample data collection is not part of the current scope of work. However, CDM Smith will check the 100-foot buffer against select geochemical modeling to determine if it makes sense to look at installations closer than 100 feet once the candidate sites are screened down to the required number of pilot-test locations. If field sample data collection at a future date is authorized by the Town based on recommendations from initial geochemical modeling, it is recommended that borings be conducted to extract geologic samples, for mineralogical testing in a laboratory, along with related geochemical tests for characterizing the likely reactions. Also, at least one of the borings should be completed as a monitoring well, from which groundwater samples would be collected, for water quality analysis. In addition, volumes of groundwater would be extracted, for subsequent geochemical tests. Then, based on the lab results, expanded geochemical modeling would be conducted, for predicting the geochemical changes along the flow path up-gradient to down-gradient of the PRB and into the discharge/seepage point to the surface waters. This would serve as the basis for making adjustments to the buffer-limit, if needed.
3.2.3 PRB Placement Relative to Nitrate Plume Locations will be selected that are known to be in zones that have been impacted by septic systems, in terms of already-measured concentrations of septic system contaminants; or, if monitoring data are not available, the selected locations will be in zones that are clearly and immediately down-gradient of high-density residential development that has been in existence long enough for sufficient development of nitrogen plumes from the residences’ septic systems.
Of primary importance in this regard is the prior body of work conducted by the Town and its consultants associated with town-wide wastewater management planning, as well as the efforts related to the Massachusetts Estuary Program led by U. Mass/Dartmouth and its SMAST group, under the overall direction of the MassDEP. In addition, the U.S. Geological Survey (USGS) has performed extensive studies and cooperative monitoring of hydrogeologic conditions and plume migration on Cape Cod, in cooperation with MassDEP and the Cape Cod Commission. These efforts have defined and characterized the groundwater flow patterns, plume extents and likely discharge seepage areas,
PRB Committee April 4, 2013 Page 28 and associated nitrogen loading potential for the watersheds within Falmouth, as part of overall efforts across Cape Cod and coastal southeastern Massachusetts. Supplementary groundwater flow and plume modeling by consultants to the Town have included some focused efforts in such areas as the West Falmouth Harbor watershed. These extensive studies provide a strong foundation for guiding the selection of appropriate locations for PRB pilot-testing, to ensure the presence of significantly nitrate contaminated groundwater from up-gradient septic systems.
3.2.4 Related Down-Gradient Impact Lessons Learned from Similar Projects The pilot-testing will leverage, to the extent feasible and appropriate, the experience gained through similar efforts, as listed in Section 1 above. The most relevant and synergistic projects in this regard include the prior test-installations of the patented NitrexTM PRB system at Waquoit Bay and Childs River Watershed; the very similar project for the Town of Brookhaven, Suffolk County, Long Island, NY; and the recent Otis AFB septage-plume PRB test-installation funded by the overall DoD/MMR aquifer-restoration program, which included significant participation by the USGS in particular.
Waquoit Bay and Childs River NitrexTM PRB Installations The “lessons learned” from the Waquoit Bay and Childs River pilot-testing of the patented NitrexTM PRB technology include the following:
The potential for PRB-caused geochemical changes to trigger negative outcomes in terms of down- gradient water quality impacts, both in terms of direct violation of standards or guidance values, as well as aesthetic impacts due to colored-water discharge to surface waters and wetlands, as mentioned above.
In addition, the Childs River installation included identification of a deeper-than-anticipated nitrogen plume, and therefore such an outcome needs to be avoided during the upcoming pilot- demonstration PRB installations.
As a result of the water quality and aesthetic impacts, and the unanticipated plume depth at one of the demonstration sites, the “lessons learned” lead to guiding principles in terms of the need for understanding why the impacts occurred and why the plume was so deep; this understanding therefore leads to the requirement to select PRB locations and depths that will avoid such outcomes.
In regard to understanding why the outcomes occurred, the project reporting includes some clues, but the forensic efforts appear to have been too limited to be certain that the reasons have been fully identified. Therefore, it would be prudent to conduct focused groundwater flow, plume migration, and local-scale geochemical modeling in which the specific situations at the Waquoit Bay and Childs River PRB installations would be simulated, with the modeling called on to reproduce the plume depths and the water quality down-gradient changes. This groundwater flow/plume migration and geochemical modeling should be conducted during the next stage of this current PRB piloting project, and the results used to define how to avoid such impacts. It is anticipated that the
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primary result will be confirmation (or refinement or adjustment) of the 100-ft buffer distance, discussed above.
It is also anticipated that the recommended modeling will provide insight regarding the density and placement of subsurface monitoring points, for measuring geochemical changes adequately, and for ensuring that the down-gradient groundwater concentrations are returning to acceptable values within the buffer zone. Also, the modeling would lead to a monitoring location design that includes multi-level wells with ports that are deep and densely-spaced sufficiently for adequate coverage and characterization of the contaminated groundwater.
In addition, it is expected that the prior PRB-related studies conducted in relation to MMR plumes, by the USGS and AFCEE/MMR contractors, will provide the basis for focused discussions with the technical leaders of those efforts, in regard to avoiding deleterious down-gradient impacts – including the kind that occurred due to the Waquoit Bay PRB demo-project.
Brookhaven Long Island PRB The Long Island project is about a year or two ahead of the efforts in Falmouth. By the time the Falmouth pilot-testing initial design and approvals are completed, Brookhaven is anticipated to have four pilot-test PRBs constructed, with the associated monitoring systems producing initial results. CDM Smith has been involved in this application of PRB technology for septic system related nitrogen control from the very beginning of its concept stage. Thus, any and all “lessons learned” from Brookhaven will be applied to the Falmouth PRB pilot-testing, and the potential subsequent full-scale implementation. Per the Town’s request, CDM Smith is currently in discussions with Brookhaven and our colleagues on the overall project team (SUNY Stony Brook and Cornell University) toward obtaining approval for release of technical specifications, monitoring data, as-yet-unpublished reporting, and “lessons learned” – as well as formulating a consensus-based plan for ongoing sharing of such information. It is expected that this will be resolved within the next month.
Ashumet Pond PRB The advantages to be gained from the phosphorus-control PRB installed up-gradient of Ashumet Pond by the USGS and others include the following aspects:
Monitoring system lay-out and types of monitoring points, including custom-designed vs. commercially-available multi-level groundwater sampling points, in-pond groundwater seepage sampling devices, water level and water quality probes and associated data recorders.
Aesthetic impacts associated with ZVI based media. Promptly after installation of the PRB, oxidation of the iron based media produced a rust colored stain on the banks of Ashumet Pond.
Use of ZVI media in the PRB for attenuating the target nutrient, phosphorus, as well as the associated effectiveness performance monitoring related to nitrogen attenuation.
Application of regional scale down to very localized numerical modeling of groundwater flow patterns, including the effects of the PRB and the interaction between the groundwater flow field
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and the pond; along with linked simulation of nutrient fate and transport, using multiple types of modeling techniques, ranging from desktop geochemical methods to fully-3D mass transport modeling.
3.2.5 Research Partnerships The pilot-testing should also leverage efforts that are currently being planned by agencies such as the USGS and USEPA. This guiding principle, therefore, is very similar to the one focusing on gaining knowledge and benefitting from “lessons learned” on other PRB/nitrogen projects that have already been conducted, or are underway elsewhere. Here are several compelling reasons for leveraging related efforts that are currently being planned out, or which are in early stages of conceptual formulation:
Shared and/or cooperatively-funded costs for conducting the studies could be arranged, with the highest-likelihood being cooperative funding with the USGS.
The potential for teaming together for securing R&D and other types of funding, with the notion that any submittals for such funding would be greatly strengthened by including respected, recognized expert organizations and individuals.
Direct involvement of experts who have conducted similar projects on Cape Cod.
Research-science organizations and regulatory agencies are paying close attention to PRB pilot- testing for nutrient removal, given the nationwide extent of the problems caused by nutrients in groundwater and surface water. Thus, they are certain to be very interested in this current pilot- testing project – which is likely to trigger willingness on their part to discuss the potential for leveraging their resources, per the items listed above.
Given the potential leveraging of interested organizations’ resources, further elaboration of this guiding principle involves citing of key examples of specific R&D topics they are likely to be considered right now. The following topics include ones that are known to be of interest based on prior R&D studies, and also subjects that have arisen during various ad hoc interactions with agency experts as well as internally at CDM Smith in regard to similar projects being conducted in various locations:
Characterization of specific in-situ types of highly local conditions/situations, with an emphasis on complementing and/or extending the findings from prior similar efforts, or exploring whether prior findings can be generalized or whether site-specific assessment is needed. Here are some specific R&D subjects in this category:
- Saline-freshwater groundwater flow dynamics and the potential geochemical impacts on PRBs placed close to the interface / recirculation zone. This is known to be of significant interest to research organizations, based on CDM Smith involvement on the Brookhaven Long Island PRB nitrogen project.
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- Potential for “focusing” of groundwater flow through the installation of higher-than-ambient permeability PRB media, but while also meeting the requirement for retention time within the media so that sufficient nitrogen attenuation can be achieved. The “focusing” aspect is of interest because of the potential for avoiding underflow and flow-around-the-ends. In addition, this variation from the basic criterion of matching the ambient permeability also has the potential to capture a wider (and deeper) portion of the up-gradient plume with a PRB length (and depth) that does not extend across the entire width (and depth) of the plume.
Characterization of the local groundwater flow and water quality patterns in specific focus-areas, as follows, noting that this provides the basis for helping set priorities during the site selection process:
- “Necks” that are south of Route 28, because of the significantly different flow patterns there vs. the “inland” areas north of Route 28, in conjunction with the prevalent relatively dense residential land use. In addition, the necks have not been included in groundwater monitoring networks, and thus there is further need for devoting resources to this area.
- Nutrient plume discharge zones, with emphasis on locations where plumes are discharging to saline waters (i.e. estuaries) and wetlands, as indicated by groundwater flow and contaminant transport theory, monitoring data and hydrogeological mapping, and also associated numerical simulation modeling.
Application and/or testing of certain types of monitoring equipment and techniques, with emphasis on methods and materials that may still be in the R&D mode, as one basis for helping to secure support (funding or cooperative/in-kind services) and to ensure appropriate levels of “research” for certain organizations (academic, USGS, and WHOI-related entities, for example). The following are recommended for specific consideration on the current project, because of known interest and/or application on other similar projects, and/or because of the strong potential for linking into R&D funding sources, or a widespread acknowledgement of a potentially significant benefit:
- Nitrate probes/sensors are now available that offer the potential for use in environmental monitoring applications, and some of them are currently being evaluated by the USGS (and other entities). On the CDM Smith project for Jacksonville, Florida, the City is at present discussing the possibility for the USGS to provide one of these sensors under a cost-share or other similar cost-beneficial arrangement; this is based on the great interest of USGS in testing the probe-technology in that area of the country, for complementing similar testing elsewhere, in a different climatic and hydrogeologic setting. The Jacksonville implementation is expected to occur within the next 2 or 3 months, and thus the results could provide information for use in Falmouth.
- Multi-port groundwater monitoring installations, as either vertical or horizontal wells, have proven successful on hundreds of sites/projects around the world – with the success measured in terms of the benefit-cost ratio related to the number of sampling points and resultant
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monitoring network density (laterally and vertically); thus, they should be considered for this current project. Of specific significance and synergy is the fact that the USGS and AFCEE contractors working on the MMR project installed such devices for monitoring the performance of the PRB installed up-gradient of Ashumet Pond for removing groundwater- borne phosphorus. This successful application of cost-efficient technology indicates the likelihood that it would be similarly successful for the current pilot-testing project.
- Seepage meters, seepage zone monitoring points, and other in-pond/in-stream devices/techniques for measuring groundwater flow rates and/or water quality. Several types of devices have been developed within this overall category, and other similar projects have produced results that will be very useful for the current project, through implementation of such devices along with confirmatory, complementary measurements using other techniques. In particular, the Brookhaven Nitrogen PRB and Ashumet Pond Phosphorus PRB projects have included successful deployment of these types of devices, with the successes transferable to the monitoring that will be conducted for the Nitrogen PRBs to be pilot-tested in Falmouth. In addition, the “lessons learned” in this regard from these two projects are advantageous because the Ashumet Pond situation is representative of an up-gradient, non-coastal situation, while the Waquoit Bay, Childs River, and Brookhaven cases demonstrates techniques applicable for coastal or near-coastal, tidally-affected conditions. Because the Falmouth sites that are most likely to be considered and selected are in the latter category, the two prior Falmouth demonstrations projects and the currently-being-implemented Brookhaven project are providing information and results-derived conclusions and recommendations that are anticipated to be of greater interest. In addition, it is also anticipated that USGS and USEPA interest in saline-freshwater seepage monitoring could foster USGS cooperative assistance in the implementation of appropriate monitoring devices for such a situation, using their Cape Cod specific experience and the extensive technical-expert network they maintain. Such an application would be highly beneficial for the Falmouth pilot-testing, under the assumption that at least one of the pilot PRBs will be located relatively close to a saline-freshwater boundary zone.
3.2.6 Regulatory Requirements Set expectations from the start in regard to the difference between the monitoring needed for pilot- testing vs. the type of monitoring that would meet all technical and regulatory requirements during full-scale implementation. This needs to be done by making it clear to all participating regulatory agencies and potentially-impacted stakeholders that the detailed, dense, and frequent type of monitoring conducted during PRB pilot-testing is needed for “proof-of-concept” purposes. Once the pilot-testing demonstrates that PRB performance indicates that full-scale implementation would be feasible and cost-effective, a different set of monitoring goals and objectives, along with associated metrics, would be defined – leading to a significantly reduced density and frequency of monitoring in comparison to the intensive type conducted during pilot-testing. In essence, it must be stressed that the pilot-test monitoring program will be designed and conducted for meeting scientific/engineering purposes, with the overall purpose to provide assurances that full-scale implementation would
PRB Committee April 4, 2013 Page 33 achieve regulatory/stakeholder requirements; however, the primary purpose of the long-term monitoring program would be to collect data demonstrating regulatory compliance, although the full- scale implementation (given appropriate partnering and potential leveraging of R&D funding) could also include monitoring specifically-designed for scientific purposes.
These guiding principles provide one part of the overall foundation for proceeding expeditiously with the selection of pilot-test locations, while ensuring that the pilot-testing will be conducted in locations that provide an adequate demonstration of the range of situations to be encountered during full-scale implementation.
4.0 Summary A comprehensive assessment of existing PRB research that has been performed specifically for the treatment of nitrate was conducted as part of this technical memorandum. In total, 10 full scale PRBs were identified as being constructed for the treatment of nitrate in groundwater. In most instances, the PRBs were designed as a trench style PRB with organic carbon reactive media. Several of the PRBs that were designed for multi-contaminant treatment, included an inorganic media, such as zero- valent iron, as well as organic carbon substrate, which both served as a means of nitrate reduction. Operating PRBs have been shown to be capable of reducing nitrate concentrations by 70 to 100%. Removal and longevity of the PRB will greatly depend on media type, influent nitrate concentrations and other site specific factors discussed in further detail in Sections 1 and 3 of this memo. Research indicates that organic media based PRBs are capable of successfully operating for longer than 15 years. The most significant siting concern for Falmouth is the PRBs proximity to tidal waters. In order to maximize performance of longevity of the PRB, tidal inundation should be avoided.
In order to assess permitting requirements for a pilot PRB installation, a list of all potentially applicable permits has been compiled. A description of the permits and approvals that would be required at the federal, state, regional and municipal level was discussed along with estimated time to prepare each of the permits and time for final approval.
A detailed discussion of potential down-gradient impacts was discussed in Section 3 of this memorandum. Important design considerations that were identified in Section 1 such as: matching transmissivity of the groundwater and PRB media, longevity of the PRB, grading during construction, water quality differences between groundwater at different sections in and around the PRB, and tidal impacts were addressed in greater detail. Lessons learned from past studies, with regard to down- gradient impacts of PRB installations were also discussed, with an emphasis on applicability to Falmouth, MA. Potential research partnerships were identified, in order to maximize currently available resources for PRB and nitrate removal on the Cape.
Based on the review of available PRB scientific information, potential permitting needs, and our understanding of potential down-gradient impacts and subsequent siting, design, construction and monitoring considerations, CDM Smith is of the opinion that PRB demonstration projects can be successfully located in Falmouth.
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5.0 Summary of Comments from March 13, 2013 Project Meeting This section summarizes the comments from participants at the March 13, 2013, project meeting that are relevant to Technical Memorandum No. 1. The comments are addressed below and/or in the relevant sections of Technical Memorandum No. 1.
Provide dimensions of the PRB installed in Southern Ontario (Long Point Site) that was in place for 15 years as well as available dimensions for any of the other PRB projects identified in Tables 1-1 and 1-2.
The PRB demonstration projects should be greater than 100 feet in length, much greater. Perhaps 500 to 1,000 feet in length.
In terms of regional impacts of the PRBs and potential permitting/approval requirements, the Cape Cod Commission will most likely not take jurisdiction over the PRB demonstration projects and the PRB demonstration projects most likely will not exceed thresholds that trigger Development of Regional Impact approval.
In response to questions about the need for permits related to monitoring, monitoring wells are generally exempt from the Wetlands Protection Act so monitoring wells installed in water body or wetlands should be a non-issue. However, MassDEP Waterways Division will also weigh in on whether a well is considered a structure.
GHD screened out PRBs as a feasible alternative in the CWMP process. At the meeting, the need to further discuss PRBs with MEPA from a big picture regulatory standpoint was discussed. In particular, the discussion centered on the concept of continuing to pollute groundwaters of the Commonwealth with nitrogen discharges from septic leaching fields, then treating the groundwater using a PRB prior to discharge to a Federal surface water subject to TMDLs. In general, the groundwater permitting program under MassDEP is already designed to manage the impacts to groundwater, for example allowing the siting of septic tank systems through Title 5. In essence the state has processes in place to manage the groundwater and meet the public trust. However, the use of PRBs as an accepted, long-term wastewater management practice is an important global question that will need further discussion. A more definitive scope of required permits will be determined once specific installation locations have been identified. Technical Memorandum No. 3 will build upon the general permitting requirements provided in Technical Memorandum No. 1 and provide a finer-grained evaluation of permitting requirements at a site location level.
Don’t immediately drop out sites within the 100-foot buffer of estuaries. CDM Smith will check the 100-foot buffer against geochemical modeling to determine if it makes sense to look at installations closer than 100 feet.
In Table 1-4, qualify hydraulic conductivity discussion that PRB will match hydraulic conductivity of the surrounding aquifer to the extent possible.
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6.0 Works Cited AFCEE. (2008). Technical Protocol for Enhanced Anaerobic Bioremediation Using Permeable Mulch Biowalls and Bioreactors. U.S. Aie Force.
CH2M HILL. (2007). Final Ashumet Pond 2006 Phosphorous Barrier Technical Memorandum. Otis ANGB.
Fahrner, S. (2002). Groundwater Nitrate Removal Using a Bioremediation Trench. University of Western Australia.
Feinberg, D. S. (2010). Wood decomposition after five years in anaerobic nitrate rich groundwaters: Implications for lifetime of Nitrex™ Permeable Reactive Barriers. Woods Hole: The Ecosystems Center, Marine Biological Laboratory.
Feng, H., Wang, H., & Jing, L. (2012). Mixture of Walnut Shell and Sand used to Nitrate removal in Groundwater. Advanced Materials Research, 459-466.
Gavaskar, A., Sass, B., Gupta, N., Hicks, J., Yoon, S., Fox, T., et al. (2002). Evaluating the Longevity and Hydraulic Performance of Permeable Barriers at Department of Defense Sites. Port: Naval Facilities Engineering Service Center.
Gilbert, O., Pomierny, S., Rowe, I., & Kalin, R. M. (2008). Selection of organic substrates as potential reactive materials for use in a denitrification permeable reactive barrier (PRB). Bioresource Technology, 7587-7596.
Hosseini, S. M., Ataie-Ashtiani, B., & Kholghi, M. (2011). Bench-Scaled Nano-Fe0 Permeable Reactive Barrier for Nitrate Removal. Ground water Monitoring and Remediation, 82-94.
Israel, S. (2006). In Situ Denitfirication of Nitrate Rich Groundwater in Marydale, Northern Cape. Department of Soil Science, Stellenbosch University.
ITRC. (2005). Permeable Reactive Barriers: Lessons Learned/New Directions. Washington, DC: The Interstate Technology & Regulatory Council.
ITRC. (2011). Permeable Reactive Barrier: Technology Update. Washington, DC: The Interstate Technology & Regulatory Council.
Kaszuba, J. P., den Baars, S. P., Longmire, P., Strietelmeier, B., Taylor, T., Cota, T., et al. (2004). Design, Installation and Performance of a Multi-Layered Permeable Reactive Barrier for. Los Alamos National Laboratory.
Lee, S., Lee, K., Rhee, S., & Park, J. (2007). Development of a New Zero-Valent Iron Zeolite Material to Reduce Nitrate without Ammonium Release. Journal of Environmental Engineering, 6-12.
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MACTEC, Inc. (2002). Demonstration of a Columnar Wall Jet Grouting of a Permeable Reactive Treatment Wall.
Massachusetts Department of Environmental Protection. (2011, May). Water Quality Assessments. Retrieved February 20, 2013, from Massachusetts Department of Environmental Protection: http://www.mass.gov/dep/water/resources/wqassess.htm#wqar
Moon, H. S., Chang, S. W., Nam, K., Choe, J., & Kim, J. Y. (2006). Effect of reactive media composition and co-contaminants on. sulfur-based autotrophic denitrification, 802-807.
Moreau, S. (2005). Influence of NIRTEX barrier on groundwater flow paths, dissolved organic carbon and nitrate concentrations. Woods Hole: The Ecosystems Center, Marine Biological Laboratory.
Roberston, W. (2010). Nitrate removal rates in woodchip media of varying age. Ecological Engineering, 1581-1587.
Roberston, W. D., Blowes, D. W., Ptacek, C. J., & Cherry, J. A. (2000). Long-Term Performance of In Situ Reactive Barriers for Nitrate Remediation. Ground Water, 689-695.
Roberston, W. D., Vogan, J. L., & Lombardo, P. S. (2008). Nitrate Removal Rates in a 15-Year-Old Permeable Reactive Barrier Treating Septic System Nitrate. Ground Water Monitoring and Remediation, 65-72.
Robertson, W. D., Ptacek, C. J., & Brown, S. J. (2009). Rates of Nitrate and Perchlorate Removal in a 5- Year-Old Wood Particle Reactor Treating Agricultural Drainage. Ground water Monitoring and Remediation, 87-94.
Robertson, W. D., Ptocek, C. J., & Brown, S. J. (2007). Geochemical and Hydrogeological Impacts of a Wood Particle Barrier Treating Nitrate and Perchlorate in Ground Water. Ground Water Monitoring and Remediation, 85-95.
Rocca, C. D., Belgiorno, V., & Meric, S. (2006). Heterotrophic/autotrophic denitrification (HAD) of drinking water: prospective use for permeable reactive barrier. Delsalination, 194-204.
Schipper, L. A., Gregory, B. F., Hadfield, J. C., Vojvodic-Vukovi, M., & Burgess, C. P. (2004). Hydraulic constraints on the performance of a groundwater denitrification wall for nitrate removal from shallow groundwater. Contaminant Hydrology, 263-279.
Su, C., & Puls, R. W. (2007). Removal of added nitrate in the single, binary, and ternary systems of cotton burr compost, zerovalent iron, and sediment: Implications for groundwater nitrate remediation using permeable reactive barriers. Chemosphere, 1653-1662.
Taylor, T. P., Longmire, P., Counce, D. A., Chipera, S. J., Kaszuba, J. P., & Conca, J. L. (2002). Permeable Reactive Barrier Treatment technology for Remediation of Inorganic-Contaminated Groundwater. Remediation of Chlorinated and Recalcitrant Compounds. Monterey: Battelle Press.
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USEPA. (1998). Permeable Reactive Barrier technologies for Contaminant Remediation. Washington DC: USEPA.
Vallino, J., & Foreman, K. (2008). Effectiveness of Reactive Barriers for Reducing N-Loading to the Coastal Zone. Woods Hole: CICCET.
Vincent, A. (2006). The Effects of Seawater Intrusion on Microbial Nitrate and Sulfate Reduction within a NITREXTM Permeable Reactive Barrier Designed to Mitigate Groundwater N-Pollution. Woods Hole: The Ecosystems Center, Marine Biological Laboratory.
Yamada, S., Suemasa, N., Kaada, T., Nagaoka, H., & Nomura, E. (2006). A Fundamental Study on In-Situ Method for Removal of Nitrate-Nitrogen Contaminated Groundwater. ASCE.