A Study of Road Deicer Pathways in a Small Headwater Catchment in Southeastern Massachusetts
Total Page：16
File Type：pdf, Size：1020Kb
A Study of Road Deicer Pathways in a Small Headwater Catchment in Southeastern Massachusetts Author: David Michael Beutel Persistent link: http://hdl.handle.net/2345/bc-ir:104633 This work is posted on eScholarship@BC, Boston College University Libraries. Boston College Electronic Thesis or Dissertation, 2015 Copyright is held by the author, with all rights reserved, unless otherwise noted. Boston College The Graduate School of the Morrissey College of Arts & Sciences Department of Earth and Environmental Sciences A STUDY OF ROAD DEICER PATHWAYS IN A SMALL HEADWATER CATCHMENT IN SOUTHEASTERN MASSACHUSETTS a thesis by David M. Beutel submitted in partial fulfillment of the requirements for the degree of Master of Science August 2015 © Copyright by David M Beutel 2015 Abstract Title: A Study of Road Deicer Pathways in a Small Headwater Catchment in Southeastern Massachusetts Author: David M. Beutel Advisor: Rudolph Hon Road salt deicers are necessary for road safety, yet pose a risk to wildlife and public water supplies by increasing major ion loads above EPA limits. To better understand the fate of deicers after application, we need to know the migration routes and subsurface pathways that deicers take from their sources to points of discharge. This project used sediment core analysis and major ion chemistry analysis of water quality to evaluate the pathways of NaCl and CaCl2 through the subsurface of a shallow glacial aquifer in south east New England. Assessment of sediment cores revealed a heterogeneous subsurface with great variation in hydraulic conductivity. Analysis of major ion concentrations and ion ratios showed both short, direct pathways and deeper, longer pathways indicative of yearly salt retention in the aquifer. Ion chemistry also revealed deicer sources by their variable NaCl to CaCl2 ratios. Acknowledgements I would like to thank my advising committee Dr. Rudolph Hon and Dr. Corinne Wong for their guidance and support on this project. I would also like to thank Dr. James Besancon of Wellesley College for his technical support and assistance with sample analysis throughout my time at Boston College. Without their patience, hard work, and leadership, this project would never have been possible. Second, I would like to thank Jack McInnis, Peter Dillon, and everyone at the Norwell Water Department for their generosity and access to resources needed to complete this project. Thanks to Laila Parker and Michelle Craddock from the DER. Thank you to my classmates, specifically Bianca Bello, Kendall Valentine, and Stephen Hilfiker for incredible support and positive vibes every step of the way. Finally, thanks to my wife Dr. Kristen Bottema-Beutel for happily listening to hundreds of hours of me rambling on about groundwater chemistry. i Table of Contents Acknowledgements ............................................................................................................ i List of Figures ................................................................................................................. iii List of Tables .................................................................................................................. iv List of Equations ............................................................................................................. iv Section 1. Introduction ..................................................................................................... 1 1.2 Current State of Groundwater in New England ............................................................. 3 Section 2. Field Site ......................................................................................................... 9 Section 3. Objective ....................................................................................................... 15 Section 4. Methods ........................................................................................................ 16 4.1 Surface Water Sampling .......................................................................................... 16 4.2 Ground Water Sampling .......................................................................................... 16 4.3 Water Sample Analysis ........................................................................................... 17 4.4 Sediment Core Analysis .......................................................................................... 21 4.5 Pump testing – drawdown characterization ................................................................ 22 Section 5. Results .......................................................................................................... 23 5.1 Analysis of Subsurface Pathways ............................................................................. 23 5.2 Drawdown measurements ........................................................................................ 29 5.3 Estimating salt inputs and evaluating impact on water quality ...................................... 30 Section 6. Discussion ..................................................................................................... 45 6.1 Differential Deicer Pathways ................................................................................... 45 6.2 Water chemistry as an indicator of different deicers and source .................................... 49 6.3 Road density regions above the Old Pond Meadow aquifer .......................................... 54 6.4 Year-round elevated Cl- levels in Third Herring Brook ................................................ 57 6.5 Water quality differences between NOR-1 and NOR-6 ............................................... 60 Section 7. Conclusion ..................................................................................................... 64 Section 8. References ..................................................................................................... 66 ii List of Figures Figure 1 – Percent of total dissolved solids (TDS) attributed to road salt deicers ............. 7 Figure 2 – Chloride concentration of water samples. ....................................................... 8 Figure 3 – The Old Pond Meadow Aquifer in Norwell, Massachusetts. .......................... 10 Figure 4 – Surficial geology of the Old Pond Meadow Aquifer. ...................................... 11 Figure 5 – Monitoring well and public supply well locations. ......................................... 12 Figure 6 – The THB watershed and OPM aquifer in Norwell, Massachusetts ................ 14 Figure 7 – Cation concentrations of internal standard samples ..................................... 19 Figure 8 – Anion concentrations of internal standard samples. ...................................... 20 Figure 9 – TDS and specific conductivity of water samples taken from THB ................. 21 Figure 10 – Ground water contours of the Old Pond Meadow aquifer. .......................... 24 Figure 11 – Sediment core taken in the wetlands next to Monitoring Well 3. ................. 25 Figure 12 – Grain size analysis of sediment core taken near MW1 ............................... 26 Figure 13 – Sediment cores taken from the glacial outwash region ............................... 27 Figure 14 – Grain size analysis of sediment core taken near monitoring well 7 ............. 27 Figure 15 – Estimated hydraulic conductivity of samples .............................................. 28 Figure 16 – THB monitoring well response to pumping by NOR-1 ................................. 29 Figure 17 – Land use map of the watershed. ................................................................ 32 Figure 18 – Land use in the THB watershed ................................................................. 33 Figure 19 – Salted impervious surfaces around Hanover Mall ....................................... 34 Figure 20 – Six months of specific conductance measurements ................................... 35 Figure 21 – Cl- concentration of THB surface water....................................................... 36 Figure 22 – Cl- concentration and Na/Ca ratio of surface water samples ....................... 38 Figure 23 - Spatial distribution of average water quality parameters .............................. 42 Figure 24 - Cl- concentration of THB monitoring well samples ....................................... 43 Figure 25 - Wetland regions adjacent to public supply wells and Third Herring Brook ... 47 Figure 26 - Nine sediment cores alligned South to North ............................................... 48 Figure 27 - Na/Ca ratio v Chloride Concentration of water samples .............................. 50 Figure 28 - A large pile of rock salt exposed to the elements at the salt storage shed ... 51 Figure 29 - An empty bag of Peladow deicer found in a snow bank ............................... 52 Figure 30 - Na/Ca ratio of monitoring wells along Third Herring Brook .......................... 53 Figure 31 - Roadways and impervious surfaces above the OPM. .................................. 55 Figure 32 - Groundwater pathways ............................................................................... 57 Figure 33 - Three water sources within the Old Pond Meadow Aquifer.......................... 61 Figure 34 - Modeled pathways of groundwater into NOR-1 and NOR-6 ........................ 63 iii List of Tables Table 1 – Average Ca2+, Na+, and Cl- levels monthly sampling in HBW6 ......................... 4 Table 2 – Major ion chemistry from the USGS NAWQA NECB land-use project. ...........