The total weight of clastic sediment particles sequestered this website within the pond since 1974 was calculated from sediment volume (obtained from bathymetry maps of the pond floor in 2012 and survey maps of the regarded pond floor in 1974). This weight was additionally corrected for organic-matter content and compaction provided by cores collected in an even spatial distribution across the pond (Fig. 6). Bathymetry was measured

relative to bankfull pond level (as determined by the spillway) using a measuring stick from a kayak in June of 2012 (Fig. 6). Depth measurements were utilized to construct a GIS-based raster surface of the pond floor using a nearest-neighbor interpolation method; a second surface model of the post-excavation pond floor in 1974 was based on survey maps of the pond provided by the Mill Creek Park Service (Fig. 7). Depths to the 1974 hard ground below the soft pond sediments, measured at coring locations, served NU7441 as control on the vertical datum and provided a means of integrating the two

data sets. The modern shoreline position, digitized from aerial photography, provided points of zero depth value for use in subsequent surface and volume modeling. A subtraction map of these two surfaces (i.e. 2012–1974) provided a net-thickness (i.e. volume) map for the time interval of interest to be used for an assessment of the clastic sediment contribution from surrounding hillslopes (Fig. 7). A total of 8 sediment cores were collected in an even distribution

across the pond using a push-coring device (Fig. 6 and Table 2). A 3″ aluminum core barrel was pushed through the soft sediment to the underlying hard ground (i.e. till or sedimentary rock). The difference in distance from the top of the corer to the sediment–water interface along the outside and inside of the core tube, respectively, provided a measure of core compaction, which provided a correction factor (Cc) for the volume to dry weight calculation ( Fig. 7). Compaction PAK6 for all cores averaged ∼30%, but ranged from 10% to 50% ( Table 2). Cores were halved in the lab length-wise, photographed, described, and sub-sampled at 2.5 cm-intervals for loss on ignition and grain-size analysis of the clastic component. LOI was performed using the standard procedure outlined by Schumacher (2002). Post-LOI grain-size analysis was performed using the standard dry-sieve method. A 63 μm-sieve was used to isolate the silt/clay component from the sand constituency. The USLE estimates soil loss in t/acre/yr (Wischmeier and Smith, 1978); the analysis therefore required a conversion from sediment volume, determined by the subtraction of the survey-derived surface model of the 1974 pond floor from the 2012 bathymetry-derived surface model of the modern pond floor, to dry inorganic sediment weight. Pristine core halves were used to generate a conversion factor for deriving dry sediment weight from volume (Cvw).