Progress Report

CICEET Progress Report for the period 3/15/05 Through 9/15/05

Project Title: Effectiveness of Reactive Barriers for Reducing N-Loading to the Coastal Zone
Principal Investigator(s): Joseph Vallino and Kenneth Foreman
Additional Investigator(s): Pio Lombardo
Project Start Date: 1 September 2004

Figures
Figure 1

Figure 1
Figure 2a

Figure 2a
Figure 2b

Figure 2b
Figure 3a

Figure 3a
Figure 3b

Figure 3b
Figure 4

Figure 4
Project Objectives for This Reporting Period
Objectives
The primary objective for this period was to install the NITREX® permeable reactive barriers (PRBs) at Sites 1 (Waquoit Bay) and 4 (Apicella residence) (see Figure 1) and begin monitoring wells for NO3-, NH4+, biological oxygen demand (BOD), dissolved organic carbon and nitrogen (DOC, DON) and argon-nitrogen mass ratio. Wells were to be sampled biweekly to monthly to determine transient response of nutrient leaving barriers. Once steady state conditions develop (expected after a few months of operation), we will begin measurements and mass balances that will allow us to determine the extent that incoming NO3- is either immobilize, denitrified, or converted to DON, as well as the effectiveness of the PBRs at removing groundwater NO3-.

Tasks to meet objectives

  • Formalize design of PRBs at Sites 1 and 4.
  • Obtain permit for installation of the PRBs at sites 1 and 4.
  • Install sample wells upstream of the PRBs prior to PRB installation to obtain further background data on N loading and hydrology.
  • Hire contractor and install PRBs at Site 1 first, then at Site 4. Install wells in PRB and downstream of PRB as described in proposal.
  • Following installation, wells will be monitored for dissolved nutrients so as to determine when steady state operation of the PRB commences.

Progress on Tasks

  • Groundwater wells were installed at both Sites 1 and 4 to obtain preliminary data for PRB design (See Figure 2a and Figure 2b).
  • Designs for PRBs by Lombardo Associates commenced in April 2004 and were completed in June 2005.
  • Lombardo Associates met with Falmouth Conservation Commission on 3 March 2005 to begin permit hearings. Lombardo Associates obtained PRB installation permits from Commission on 1 June 2005.
  • Lombardo Associates hired Cavossa Excavation to install both PRB's. Construction on Apicella site commenced on 20 July and finished on 23 July 05 (Figure 3a), while construction at Waquoit site began on 4 Aug and was completed on 8 Aug 05 (Figure 3b).
  • Ground water sample wells were installed a few days following installation of PRBs at each site. However, since nutrients taken from wells parallel to length of PRB's at both Apicella and Waquoit sites showed little lateral variation, it was decided to install only one transect of wells across the middle of the PRB's (Figure 4). The well layout, which differs from that originally planned, allows us to construct a more detailed picture of changes in biogeochemistry across the PRBs. Although samples have been taken for NO3-, NH4+, DOC, DON, BOD and N2/Ar ratios in all wells at 0.5 m depth increments at both sites, analysis of the samples has not been completed at this time.
  • Since PRB's were recently installed, transient conditions prevail. We expect the transient response to diminish by March 2006.

Difficulties
The main difficulty faced to date regards the depth of the NITREX® PRB media. Our groundwater samples show that a nitrate plume maximum exists at approximate 2.5 to 3.0 m below the water table at both sites (Figure 2a and Figure 2b). However, trenches could only be excavated to approximately 2.0 m below the water table using the techniques that were budgeted for in the proposal (i.e., trench box). Although installations of NITREX® PRB's at other locations have show that the increase of hydraulic conductivity due to the NITREX® media allows the PRB to capture water from a lower depth than the base of the PRB, preliminary MODFLOW simulations at the Waquoit site indicated that the nitrate maximum may flow beneath the PRB. However, even if the maximum of the nitrate plume does not pass through the barrier, groundwater with high nitrate concentration will still enter the PRB, so the effectiveness of the NITRE® PRB can still be assessed.

Project Objectives for Next Reporting Period

Objectives
Wells at both sites will continued to be sampled on an approximately monthly basis for NO3-, NH4+, DOC, DON, BOD and N2/Ar ratios. Once data indicate that nutrient processing by the NITREX® PRB has reached pseudo steady state, we will construct a detailed nitrogen mass balance around the PRB to determine the fate of the groundwater nitrate.

Tasks to Meet Objectives
Sample groundwater wells and analyze for nutrient concentrations. Other wells may be installed as necessary as dictated by collected data.

Work Plan for Next Reporting Period
We plan to sample wells on a monthly basis; however, sampling may be difficult and less frequent in the winter months.

Anticipated Success in Meeting Project Objectives
We foresee no problems with proposed objectives and anticipate success.

Overall Project Timeline Update
Although installation of the NITREX® PRBs were about two months later than originally planned due to permitting process, this delay has not altered our original timeline significantly.

Preliminary Data
See Figures.

Dissemination
Publications:
Roberson, W.D., Ford, G.I. and Lombardo, P.S. (2005) Wood-based filter for nitrate removal in septic systems. Transactions of the ASAE, 48 (1): 121-128.

Robertson, W.D., Yeung, N., van Driel, P. W., and Lombardo, P. S. (2005) High Permeability Layers for Remediation of Ground Water; Go Wide, not Deep. Ground Water 43 (4):574-581.

Workshops:
Foreman et al. Permeable Reactive Barriers: An Alternative Approach to Mitigating Groundwater N-inputs to Coastal Bays and Estuaries. Denitrification Systems Workshop at Waquoit Bay NERR, 15 March 2005, Falmouth Woods Hole.

Outreach Activities:
The project has been receiving good publicity in the Falmouth Enterprise newspaper and two articles have been published, most recently one highlighting the installation of the barrier.

Contact with End Users:
Initial contact with municipal and regional planners and citizens in the WBNERR workshop noted above.

Expenditures
Expenditures are in range anticipated for work accomplished.

End User Advisor Feedback
Name: Brian Currie
Organization: Town Planner
Location: Town of Falmouth, MA
Phone number: 508 495 7440
E-mail: bacurrie@town.falmouth.ma.us

1) At this stage, what are the potential applications for this research? Please discuss how you and others could potentially use the technology.
At this stage, the technology could be potentially used to supplement conventional nitrogen offset measures typically Imposed by regulatory boards as mitigation for wastewater Impacts associated with development.

2) What, if anything, has changed about this project's potential applicability since the last reporting period (not applicable to the first Progress Report)?
No changes.

3) Do you see any key challenges that the researchers may want to address or keep in mind?
Cost effectiveness

4) Does this report offer you enough information to adequately address the above questions?
At this time

5) Other feedback?
Carry on