Not having much success plotting 2D concentration data

I'm trying to plot what I believe to be a simple figure that will give a 2D interpolation of concentration. I've tried ggplot of the data using geom_raster (results in a blank plot), geom_density_2D_filled, geom_contour_filled (sort of work, but I was expecting different geometries in the plot, more like a concentration gradients, or concentration isolines...)

what am I missing??

I was hoping for something along the lines of a plot like this:

dat <- read_csv("example.csv")
dat %>%
   ggplot(aes(x=X_km, y=Y_km, z=Conc)) +
   geom_contour()

dat %>%
   ggplot(aes(x=X_km, y=Y_km, z=Conc)) +
   geom_contour_filled()

dat %>%
   ggplot(aes(x=X_km, y=Y_km, z=Conc)) +
   geom_density_2d_filled()

Data:

dput(dat)
structure(list(X_km = c(496.91, 496.91, 496.86, 496.91, 496.86, 
496.86, 496.91, 496.96, 496.96, 496.96, 496.96, 496.86, 496.91, 
496.91, 496.86, 496.96, 496.96, 496.86, 497.01, 496.81, 497.01, 
496.81, 497.01, 497.01, 496.81, 496.91, 496.86, 496.81, 496.81, 
497.01, 496.96, 496.81, 497.01, 497.06, 496.91, 496.81, 496.96, 
497.06, 496.76, 496.76, 496.76, 497.06, 496.76, 497.06, 496.76, 
496.86, 497.01, 497.06, 496.86, 496.76, 496.81, 497.01, 497.06, 
496.91, 497.11, 497.11, 496.76, 497.11, 496.81, 497.06, 497.11, 
496.76, 496.96, 497.11, 496.96, 496.91, 497.11, 497.16, 497.16, 
497.06, 497.01, 497.16, 497.16, 497.11, 496.86, 496.76, 497.01, 
497.06, 497.21, 497.16, 497.16, 497.21, 496.81, 497.11, 497.21, 
497.21, 496.86, 496.76, 496.81, 496.76, 497.16, 497.11, 496.91, 
496.91, 496.96, 497.21, 496.86, 497.01, 497.21, 497.06, 496.81, 
497.16, 496.512, 497.06, 496.76, 497.26, 496.96, 497.26, 497.16, 
497.26, 497.21, 497.11, 497.21, 497.11, 497.01, 497.26, 496.91, 
497.26, 497.16, 496.86, 496.96, 496.81, 497.01, 497.21, 497.26, 
497.06, 497.26, 497.06, 496.76, 497.11, 496.512, 497.31, 497.31, 
497.16, 497.31, 497.31, 497.31, 496.91, 496.86, 496.96, 497.16, 
497.26, 497.31, 497.26, 497.01, 496.81, 497.31, 496.86, 496.91, 
497.21, 497.21, 496.76, 497.06, 497.319, 497.848, 497.292, 497.832, 
497.306, 497.11, 496.96, 497.279, 496.81, 497.265, 497.252, 497.31, 
497.816, 497.239, 497.333, 497.16, 497.26, 497.11, 496.86, 496.91, 
497.36, 497.247, 496.96, 497.36, 496.81, 497.864, 497.01, 497.21, 
497.346, 497.36, 497.01, 497.81, 497.31, 497.06, 497.21, 496.76, 
497.36, 497.8, 496.76, 497.36, 497.359, 497.36, 497.262, 497.26, 
497.11, 497.88, 497.36, 497.373, 497.36, 497.16, 497.86, 496.91, 
497.31, 497.41, 497.485, 497.16, 496.86, 497.41, 496.96, 497.387, 
496.512, 497.26, 496.81, 497.41, 497.41, 497.21, 497.01, 497.278, 
496.76, 497.26, 497.401, 497.36, 497.06, 497.06, 497.41, 497.41, 
497.41, 497.895, 497.416, 497.21, 497.91, 497.31, 497.429, 497.11, 
497.294, 497.41, 497.16, 497.442, 497.46, 497.46, 497.36, 496.265, 
497.21, 497.46, 497.454, 497.46, 497.784, 497.26, 497.46, 497.911, 
497.46, 497.16, 497.46, 497.26, 497.11, 497.41, 497.468, 496.512, 
497.31, 496.86, 496.91, 497.01, 496.96, 497.31, 497.91, 496.76, 
497.479, 497.501, 497.51, 496.81, 497.06, 497.483, 497.46, 497.16, 
497.51, 497.51, 497.11, 497.36, 497.21, 497.51, 496.265, 497.499, 
497.41, 497.21, 497.469, 497.326, 497.51, 496.81, 496.265, 497.51, 
496.76, 496.86, 497.51, 497.31, 497.46, 497.927, 497.26, 497.51, 
497.515, 497.93, 497.31, 497.01, 497.56, 497.11, 497.56, 496.96, 
497.51, 496.91, 497.36, 496.96, 497.56, 497.531, 497.01, 497.06, 
497.06, 497.56, 497.56, 496.91, 497.93, 497.26, 497.56, 497.41, 
497.343, 497.11, 497.56, 497.547, 497.16, 497.924, 497.21, 497.56, 
497.16, 497.96, 497.46, 497.56, 497.56, 496.86, 497.563, 497.51, 
497.61, 497.61, 497.26, 497.205, 497.517, 497.21, 497.61, 497.31, 
497.61, 497.61, 497.908, 497.96, 497.56, 497.36, 497.41, 497.36, 
496.81, 497.86, 497.61, 497.61, 497.46, 497.61, 497.31, 497.61, 
497.06, 497.61, 497.578, 497.51, 497.96, 496.76, 497.66, 497.66, 
497.11, 497.66, 497.66, 497.26, 497.456, 497.01, 497.56, 497.61, 
496.96, 497.892, 497.377, 497.61, 497.66, 497.66, 497.797, 497.16, 
497.465, 497.91, 497.46, 497.71, 497.71, 496.91, 497.71, 497.594, 
497.66, 497.66, 497.51, 497.813, 497.71, 497.66, 497.782, 497.71, 
497.393, 497.36, 497.66, 497.766, 496.86, 497.66, 497.532, 497.76, 
497.61, 497.21, 497.71, 497.31, 497.61, 497.71, 497.76, 497.76, 
497.876, 497.829, 497.41, 497.76, 497.71, 496.81, 497.06, 496.018, 
497.845, 497.91, 497.86, 497.76, 497.71, 496.265, 497.66, 496.76, 
497.76, 497.75, 497.11, 497.26, 497.81, 497.41, 497.81, 497.81, 
497.427, 497.769, 497.01, 497.626, 497.71, 497.36, 496.96, 497.81, 
496.018, 497.76, 497.81, 497.76, 497.735, 496.91, 497.16, 497.81, 
497.76, 498.01, 497.444, 497.71, 497.86, 497.86, 497.81, 497.548, 
497.932, 497.642, 497.86, 497.66, 497.76, 497.86, 497.31, 496.86, 
497.56, 498.01, 497.86, 497.81, 497.96, 497.21, 497.41, 497.269, 
497.71, 496.81, 497.91, 497.564, 497.91, 497.91, 496.512, 497.96, 
497.86, 497.76, 497.658, 497.58, 497.36, 496.76, 497.753, 497.01, 
497.91, 497.26, 497.612, 497.81, 497.723, 497.06, 497.86, 497.91, 
497.674, 497.96, 497.96, 497.81, 497.86, 498.01, 497.643, 497.596, 
497.76, 497.91, 496.265, 497.11, 497.96, 497.628, 497.737, 496.96, 
497.86, 497.689, 497.91, 497.46, 497.71, 497.81, 497.96, 496.91, 
497.31, 497.41, 497.659, 496.86, 497.707, 497.61, 497.76, 497.81, 
496.018, 497.705, 496.76, 497.16, 497.96, 498.01, 496.81, 498.01, 
497.721, 497.71, 497.21, 497.318, 496.018, 497.36, 498.01, 497.675, 
497.26, 497.96, 496.512, 498.029, 497.91, 498.01, 496.96, 497.691, 
497.46, 498.06, 497.76, 497.96, 497.01, 497.86, 497.06, 497.11, 
498.06, 497.81, 498.01, 496.86, 496.81, 496.91, 497.31, 496.76, 
498.06, 497.16, 497.41, 497.76, 497.51, 498.11, 497.685, 497.86, 
497.21, 497.71, 498.01, 497.365, 497.66, 497.91, 498.11, 497.76, 
497.96, 498.06, 498.01, 498.06, 497.91, 497.36, 497.46, 496.96, 
497.26, 498.01, 497.76, 497.86, 498.11, 498.16, 497.01, 496.81, 
496.86, 497.06, 497.81, 496.76, 497.61, 497.509, 496.91, 498.16, 
497.51, 497.31, 498.11, 497.832, 497.11, 497.81, 497.81, 497.86, 
498.21, 497.41, 497.86, 497.16, 497.21, 496.018, 497.91, 498.06, 
496.76, 497.36, 497.91, 498.16, 498.11, 496.86, 497.46, 496.81, 
496.96, 497.96, 498.06, 498.21, 498.01, 497.81, 498.26, 496.265, 
497.26, 498.16, 497.56, 498.06, 497.01, 497.86, 496.91, 497.06, 
497.86, 497.86, 498.21, 497.31, 496.91, 497.11, 497.41, 497.51, 
497.16, 498.06, 496.81, 496.96, 497.71, 498.26, 496.76, 497.96, 
497.81, 497.91, 498.11, 497.76, 497.96, 498.16, 497.977, 497.36, 
498.01, 496.86, 497.56, 497.91, 497.66, 497.91, 497.01, 497.21, 
497.91, 498.21, 498.31, 497.61, 497.86, 498.26, 497.06, 497.96, 
497.852, 497.46, 498.06, 496.265, 498.11, 498.01, 496.018, 498.31, 
497.26, 497.11, 497.81, 497.91, 497.86, 496.76, 496.512, 498.01, 
496.86, 498.06, 497.16, 497.91, 496.81, 496.91, 496.96, 497.96, 
497.71, 498.06, 497.41, 497.66, 497.76, 497.31, 497.51, 497.56, 
498.16, 498.26, 498.36, 497.01, 497.96, 497.91, 498.21, 498.31, 
497.96, 497.61, 497.71, 497.96, 497.96, 497.96, 497.76, 498.36, 
497.46, 498.01, 498.06, 497.26, 497.86, 496.76, 497.81, 497.21, 
497.91, 498.11, 498.01, 498.01, 498.06, 497.66, 498.112, 497.06, 
497.36, 497.96, 498.06, 497.11, 498.01, 496.86, 497.96, 498.11, 
497.61, 496.91, 497.81, 497.91, 498.11, 497.86, 498.01, 498.01, 
498.06, 498.11, 498.26, 496.81, 498.11, 497.71, 497.56, 497.96, 
498.01, 498.16, 497.16, 498.11, 497.31, 498.01, 496.96, 497.86, 
498.06, 497.76, 497.91, 498.01, 498.21, 498.01, 498.01, 498.11, 
498.31, 497.96, 498.36, 498.06, 498.11, 497.66, 498.06, 498.06, 
498.16, 497.41, 498.11, 498.11, 498.11, 497.01, 497.21, 497.51, 
498.06, 498.16, 498.16, 497.81, 496.76, 496.81, 496.86, 497.96, 
498.01, 498.06, 497.91, 498.16, 498.01, 498.06, 498.16, 498.11, 
498.06, 498.16, 498.16, 497.61, 497.96, 498.16, 496.91, 498.11, 
497.76, 498.01, 498.06, 498.21, 497.46, 497.71, 498.06, 498.21, 
497.06, 497.36, 498.11, 498.16, 498.16, 498.11, 497.26, 497.86, 
498.06, 498.16, 498.06, 498.11, 498.16, 498.16, 497.51, 498.21, 
498.21, 497.11, 498.21, 496.018, 497.91, 498.06, 498.21, 496.81, 
497.01, 497.81, 498.01, 498.06, 498.21, 497.56, 497.96, 498.11, 
498.21, 497.16, 497.21, 498.11, 498.21, 498.36, 497.41, 497.76, 
497.86, 498.21, 497.66, 498.21, 496.96, 497.31, 498.01, 498.11, 
498.16, 498.31, 497.46, 498.11, 498.16, 498.21, 498.21, 496.76, 
498.11, 497.91, 498.06, 498.21, 498.26, 497.51, 498.11, 498.26, 
497.06, 497.61, 497.71, 497.96, 498.11, 498.16, 498.26, 496.018, 
498.21, 498.26, 498.26, 498.26, 498.26, 498.26, 498.26, 497.81, 
498.16, 498.16, 498.26, 498.31, 497.76, 498.26, 496.512, 497.26, 
497.36, 498.11, 498.16, 498.21, 498.26, 496.265, 498.16, 498.26, 
496.86, 497.11, 498.21, 498.26, 497.91, 498.11, 497.56, 498.06, 
498.21, 498.26, 498.26, 497.81, 498.16, 498.21, 498.31, 496.91, 
497.86, 496.96, 497.96, 498.01, 498.21, 498.31, 497.41, 498.31, 
498.31, 498.31, 497.16, 498.16, 498.26, 498.26, 498.31, 498.31, 
497.66, 498.26, 498.31, 497.46, 497.96, 498.31, 498.31, 497.31, 
497.91, 498.11, 498.16, 498.21, 498.26, 498.31, 496.76, 497.21, 
498.01, 498.06, 498.31, 496.86, 497.86, 498.31, 497.51, 497.61, 
498.16, 498.31, 498.36, 498.36, 496.81, 497.71, 497.76, 498.31, 
498.36, 497.06, 498.16, 498.31, 498.36, 498.36, 497.01, 497.81, 
498.36, 497.66, 498.36, 497.86, 498.31, 496.76, 497.36, 498.16, 
498.36, 498.36, 498.36, 497.26, 498.21, 498.21, 498.21, 498.36, 
496.91, 497.56, 498.31, 498.36, 497.11, 498.26, 498.36, 498.36, 
497.16, 497.91, 498.36, 498.225, 496.81, 496.96, 497.81, 498.36, 
498.36, 497.76, 497.41, 497.71, 498.36, 498.36, 496.86, 497.46, 
496.91, 497.61, 497.86, 498.26, 498.21, 497.31, 498.36, 498.26, 
498.31, 497.21, 497.51, 498.21, 497.66, 498.21, 498.26, 498.31, 
497.01, 497.71, 496.96, 497.56, 497.81, 498.26, 497.36, 498.26, 
497.11, 497.26, 497.76, 498.31, 497.06, 497.56, 497.66, 497.51, 
498.26, 497.61, 498.31, 497.41, 497.46, 498.36, 498.607, 497.529, 
497.01, 498.26, 498.31, 497.16, 497.71, 498.36, 496.185, 497.56, 
498.36, 498.31, 497.21, 497.66, 497.76, 498.118, 498.31, 497.06, 
497.31, 497.51, 497.61, 497.36, 497.46, 497.56, 497.71, 498.31, 
498.36, 498.31, 498.36, 497.11, 497.41, 497.61, 498.36, 497.475, 
497.36, 498.36, 497.26, 497.56, 497.16, 497.46, 498.36, 496.426, 
497.51, 497.66, 498.36, 498.36, 498.607, 497.31, 497.536, 498.607, 
497.61, 497.46, 497.51, 498.607, 496.668, 497.41, 497.876, 497.21, 
497.31, 498.607, 497.26, 497.36, 497.41, 498.607, 497.635, 498.607, 
496.91, 498.854, 498.854, 497.393, 498.854, 498.854, 498.854, 
498.607, 498.854, 497.151, 498.854, 498.854), Y_km = c(5443.274, 
5443.324, 5443.274, 5443.224, 5443.324, 5443.224, 5443.374, 5443.274, 
5443.324, 5443.224, 5443.374, 5443.374, 5443.174, 5443.424, 5443.174, 
5443.424, 5443.174, 5443.424, 5443.274, 5443.274, 5443.324, 5443.224, 
5443.224, 5443.374, 5443.324, 5443.124, 5443.124, 5443.174, 5443.374, 
5443.174, 5443.124, 5443.424, 5443.424, 5443.274, 5443.474, 5443.124, 
5443.474, 5443.324, 5443.324, 5443.274, 5443.374, 5443.224, 5443.224, 
5443.374, 5443.174, 5443.474, 5443.474, 5443.424, 5443.074, 5443.124, 
5443.074, 5443.124, 5443.174, 5443.074, 5443.324, 5443.274, 5443.424, 
5443.374, 5443.474, 5443.474, 5443.224, 5443.074, 5443.074, 5443.424, 
5443.524, 5443.524, 5443.474, 5443.374, 5443.324, 5443.124, 5443.524, 
5443.424, 5443.274, 5443.174, 5443.524, 5443.474, 5443.074, 5443.524, 
5443.374, 5443.474, 5443.224, 5443.324, 5443.524, 5443.524, 5443.274, 
5443.424, 5443.024, 5443.024, 5443.024, 5443.524, 5443.174, 5443.124, 
5443.024, 5443.574, 5443.574, 5443.224, 5443.574, 5443.574, 5443.474, 
5443.074, 5443.574, 5443.524, 5443.241, 5443.574, 5443.574, 5443.374, 
5443.024, 5443.424, 5443.124, 5443.324, 5443.524, 5443.074, 5443.174, 
5443.574, 5443.024, 5443.474, 5443.624, 5443.274, 5443.574, 5443.624, 
5443.624, 5443.624, 5443.624, 5443.574, 5443.224, 5443.624, 5443.524, 
5443.024, 5443.624, 5443.624, 5443.483, 5443.374, 5443.324, 5443.624, 
5443.424, 5443.224, 5443.474, 5443.674, 5443.674, 5443.674, 5443.074, 
5443.574, 5443.274, 5443.174, 5443.674, 5443.674, 5443.524, 5442.974, 
5442.974, 5443.124, 5443.624, 5443.674, 5443.674, 5443.2, 5443.087, 
5443.171, 5443.099, 5443.185, 5443.674, 5442.974, 5443.156, 5442.974, 
5443.141, 5443.126, 5443.574, 5443.112, 5443.111, 5443.215, 5443.674, 
5443.624, 5443.024, 5443.724, 5443.724, 5443.474, 5443.105, 5443.724, 
5443.524, 5443.724, 5443.075, 5443.724, 5443.074, 5443.23, 5443.424, 
5442.974, 5443.124, 5443.624, 5443.724, 5443.674, 5443.724, 5443.574, 
5443.124, 5442.974, 5443.374, 5443.245, 5443.324, 5443.093, 5443.674, 
5443.724, 5443.063, 5443.274, 5443.26, 5443.624, 5443.024, 5443.124, 
5443.774, 5443.674, 5443.524, 5442.98, 5443.724, 5443.774, 5443.474, 
5443.774, 5443.274, 5442.999, 5443.074, 5443.774, 5443.424, 5443.574, 
5443.724, 5443.774, 5443.081, 5443.774, 5443.724, 5443.288, 5443.674, 
5442.974, 5443.774, 5443.374, 5443.324, 5443.624, 5443.051, 5443.302, 
5443.024, 5443.074, 5443.724, 5443.316, 5443.774, 5443.069, 5443.674, 
5443.774, 5443.332, 5443.624, 5443.574, 5443.724, 5443.241, 5443.774, 
5443.524, 5443.347, 5443.474, 5443.136, 5443.774, 5443.374, 5443.038, 
5443.674, 5442.974, 5443.424, 5443.024, 5442.974, 5443.724, 5443.362, 
5443.724, 5443.057, 5443.824, 5443.824, 5443.824, 5443.824, 5443.774, 
5443.124, 5443.824, 5443.371, 5442.968, 5443.624, 5443.824, 5443.824, 
5443.368, 5443.724, 5443.824, 5443.574, 5443.674, 5443.824, 5443.774, 
5442.974, 5443.524, 5443.483, 5443.356, 5443.774, 5443.824, 5442.993, 
5443.045, 5443.374, 5443.874, 5442.999, 5443.474, 5443.874, 5443.874, 
5443.724, 5443.024, 5443.774, 5443.026, 5443.824, 5443.424, 5443.343, 
5443.024, 5443.824, 5442.924, 5443.624, 5442.924, 5443.674, 5442.924, 
5443.774, 5443.874, 5443.824, 5443.874, 5443.574, 5443.331, 5443.874, 
5442.924, 5443.874, 5443.424, 5443.374, 5442.924, 5443.016, 5442.974, 
5443.724, 5443.824, 5443.034, 5443.874, 5443.524, 5443.319, 5443.874, 
5443.011, 5443.874, 5443.774, 5442.924, 5443.074, 5443.824, 5443.474, 
5443.324, 5442.924, 5443.307, 5443.824, 5443.624, 5443.674, 5443.874, 
5442.927, 5442.956, 5442.924, 5443.774, 5443.874, 5443.724, 5443.574, 
5442.999, 5443.024, 5443.824, 5443.874, 5443.874, 5443.024, 5442.924, 
5443.174, 5443.424, 5443.474, 5443.874, 5443.824, 5442.974, 5443.524, 
5442.874, 5443.374, 5443.295, 5443.874, 5443.124, 5442.924, 5443.724, 
5443.674, 5442.874, 5443.624, 5443.774, 5442.924, 5442.984, 5442.874, 
5443.874, 5443.324, 5442.874, 5442.987, 5443.013, 5443.874, 5443.824, 
5443.574, 5442.913, 5442.874, 5442.996, 5443.174, 5442.974, 5443.674, 
5443.724, 5442.874, 5443.774, 5443.282, 5443.474, 5443.524, 5442.924, 
5442.925, 5443.624, 5443.874, 5442.9, 5443.824, 5443.002, 5442.974, 
5443.424, 5442.888, 5442.874, 5443.374, 5442.944, 5443.724, 5443.274, 
5442.874, 5443.574, 5442.924, 5443.27, 5443.874, 5443.674, 5443.774, 
5442.974, 5442.937, 5442.991, 5443.824, 5443.524, 5442.874, 5442.824, 
5442.999, 5442.95, 5442.974, 5442.962, 5443.624, 5443.474, 5443.724, 
5443.324, 5442.874, 5443.874, 5442.876, 5442.824, 5442.874, 5443.724, 
5442.974, 5443.774, 5443.824, 5442.98, 5443.148, 5442.824, 5443.258, 
5443.424, 5442.924, 5442.824, 5443.674, 5443.241, 5442.874, 5443.874, 
5443.574, 5442.868, 5442.824, 5442.824, 5443.624, 5443.524, 5443.074, 
5442.969, 5443.374, 5443.774, 5443.824, 5443.174, 5442.932, 5443.188, 
5443.246, 5443.874, 5443.274, 5443.474, 5443.724, 5442.874, 5442.824, 
5442.874, 5443.024, 5443.674, 5443.574, 5443.174, 5442.824, 5442.924, 
5442.844, 5443.324, 5442.824, 5443.824, 5442.919, 5443.774, 5443.874, 
5443.966, 5442.974, 5443.624, 5443.424, 5443.234, 5442.907, 5442.874, 
5442.824, 5443.16, 5442.774, 5443.724, 5442.824, 5442.883, 5443.524, 
5442.855, 5442.774, 5442.924, 5443.674, 5443.221, 5443.824, 5443.874, 
5443.474, 5443.574, 5443.124, 5442.858, 5442.895, 5443.374, 5443.624, 
5442.758, 5442.774, 5443.774, 5442.871, 5443.173, 5442.774, 5443.524, 
5443.209, 5443.574, 5442.924, 5443.274, 5442.874, 5443.724, 5442.774, 
5442.824, 5442.874, 5442.846, 5442.774, 5442.843, 5442.874, 5443.174, 
5443.424, 5442.758, 5443.197, 5442.774, 5442.774, 5443.674, 5443.874, 
5442.774, 5443.824, 5443.185, 5443.224, 5442.774, 5442.812, 5443.483, 
5442.824, 5443.774, 5442.834, 5442.774, 5443.624, 5442.758, 5443.094, 
5443.524, 5443.724, 5442.724, 5442.831, 5442.874, 5443.874, 5443.324, 
5443.574, 5442.724, 5443.474, 5442.724, 5442.724, 5443.824, 5443.374, 
5443.674, 5442.724, 5442.724, 5442.724, 5442.774, 5442.724, 5443.774, 
5442.724, 5442.824, 5443.274, 5442.874, 5443.874, 5442.826, 5443.424, 
5442.724, 5442.824, 5443.624, 5442.785, 5442.824, 5443.474, 5443.824, 
5443.224, 5443.524, 5443.674, 5442.974, 5443.724, 5442.924, 5442.774, 
5442.824, 5442.674, 5442.724, 5443.574, 5442.824, 5442.874, 5443.774, 
5443.874, 5442.674, 5442.674, 5442.674, 5442.674, 5443.324, 5442.674, 
5442.824, 5442.837, 5442.674, 5443.824, 5442.824, 5442.724, 5443.724, 
5443.325, 5442.674, 5443.224, 5443.274, 5443.374, 5443.874, 5442.774, 
5443.224, 5442.674, 5442.674, 5443.724, 5443.224, 5443.624, 5442.624, 
5442.724, 5443.424, 5443.774, 5443.674, 5442.624, 5442.774, 5442.624, 
5442.624, 5443.474, 5443.024, 5443.824, 5443.524, 5442.824, 5443.874, 
5443.966, 5442.674, 5443.724, 5442.824, 5443.574, 5442.624, 5443.324, 
5442.624, 5442.624, 5443.274, 5442.824, 5443.774, 5442.674, 5442.574, 
5442.624, 5442.724, 5442.774, 5442.624, 5443.074, 5442.574, 5442.574, 
5442.774, 5443.824, 5442.574, 5442.924, 5442.774, 5443.374, 5443.624, 
5442.774, 5443.224, 5443.674, 5442.929, 5442.674, 5443.174, 5442.574, 
5442.774, 5443.324, 5442.774, 5442.874, 5442.574, 5442.624, 5443.274, 
5443.724, 5443.874, 5442.774, 5442.774, 5443.774, 5442.574, 5443.424, 
5442.751, 5442.724, 5443.524, 5442.516, 5443.574, 5443.474, 5442.516, 
5443.824, 5442.624, 5442.574, 5442.724, 5442.824, 5442.724, 5442.524, 
5442.516, 5442.924, 5442.524, 5443.124, 5442.574, 5442.774, 5442.524, 
5442.524, 5442.524, 5443.274, 5442.724, 5442.974, 5442.674, 5442.724, 
5442.724, 5442.624, 5442.724, 5442.724, 5443.624, 5443.724, 5443.874, 
5442.524, 5443.324, 5442.724, 5443.674, 5443.774, 5442.874, 5442.724, 
5442.674, 5442.774, 5442.824, 5443.374, 5442.674, 5443.824, 5442.674, 
5442.874, 5442.924, 5442.574, 5442.674, 5442.474, 5442.674, 5442.574, 
5442.674, 5443.024, 5442.824, 5443.424, 5443.474, 5442.674, 5442.994, 
5442.524, 5442.624, 5442.724, 5442.874, 5442.524, 5442.774, 5442.474, 
5442.674, 5442.974, 5442.674, 5442.474, 5442.624, 5442.624, 5442.924, 
5442.624, 5443.224, 5443.374, 5442.824, 5442.874, 5443.674, 5442.474, 
5443.524, 5442.624, 5442.674, 5442.624, 5442.724, 5443.574, 5442.524, 
5443.074, 5442.574, 5442.624, 5442.474, 5442.574, 5442.724, 5442.624, 
5442.574, 5442.674, 5443.624, 5443.274, 5443.324, 5442.674, 5443.724, 
5442.574, 5443.774, 5442.674, 5442.824, 5442.624, 5442.774, 5443.174, 
5442.974, 5442.624, 5442.724, 5442.774, 5443.124, 5442.474, 5442.524, 
5442.674, 5442.624, 5442.924, 5443.024, 5442.574, 5442.424, 5442.424, 
5442.424, 5442.524, 5442.524, 5442.574, 5442.524, 5443.074, 5442.574, 
5443.424, 5442.824, 5442.624, 5443.374, 5442.624, 5442.674, 5442.624, 
5442.474, 5442.874, 5442.424, 5443.474, 5442.574, 5442.474, 5442.524, 
5442.974, 5442.624, 5442.574, 5442.474, 5442.924, 5442.474, 5442.574, 
5442.574, 5442.724, 5443.124, 5443.174, 5442.524, 5442.524, 5443.274, 
5442.774, 5443.224, 5442.524, 5442.574, 5443.524, 5442.624, 5442.674, 
5442.824, 5442.474, 5443.024, 5442.274, 5442.474, 5443.324, 5442.574, 
5442.374, 5442.424, 5442.524, 5442.424, 5442.424, 5442.874, 5442.624, 
5442.424, 5442.474, 5442.774, 5442.474, 5442.474, 5442.424, 5443.074, 
5443.724, 5442.574, 5442.524, 5442.474, 5442.624, 5442.574, 5443.574, 
5442.424, 5442.524, 5442.374, 5442.374, 5442.524, 5443.674, 5442.574, 
5443.424, 5442.474, 5442.524, 5442.724, 5442.374, 5443.224, 5442.424, 
5442.374, 5442.474, 5442.774, 5442.574, 5443.274, 5442.524, 5442.424, 
5442.574, 5442.524, 5442.374, 5443.324, 5443.174, 5442.924, 5443.966, 
5443.124, 5442.624, 5442.824, 5442.874, 5442.974, 5443.024, 5443.624, 
5442.474, 5442.374, 5442.424, 5442.474, 5442.774, 5442.474, 5442.574, 
5442.274, 5442.474, 5442.524, 5442.324, 5442.324, 5442.424, 5442.674, 
5442.274, 5443.474, 5442.424, 5442.374, 5442.424, 5442.374, 5442.724, 
5442.374, 5443.374, 5442.574, 5442.324, 5442.324, 5442.374, 5443.074, 
5442.424, 5443.224, 5443.524, 5442.524, 5442.374, 5442.424, 5442.374, 
5442.324, 5442.324, 5442.274, 5442.824, 5442.524, 5442.474, 5442.624, 
5443.024, 5442.424, 5442.274, 5442.324, 5443.574, 5442.724, 5442.974, 
5442.524, 5443.124, 5442.574, 5442.524, 5442.274, 5442.674, 5442.924, 
5442.474, 5442.324, 5442.274, 5443.424, 5443.174, 5442.274, 5442.374, 
5442.324, 5442.424, 5442.274, 5442.274, 5442.424, 5442.324, 5442.374, 
5442.874, 5442.524, 5442.524, 5443.324, 5443.624, 5442.474, 5443.674, 
5442.324, 5442.474, 5442.424, 5443.074, 5442.724, 5442.374, 5443.274, 
5442.324, 5442.674, 5442.774, 5442.374, 5442.374, 5442.524, 5442.474, 
5443.024, 5442.324, 5443.124, 5442.274, 5442.474, 5443.374, 5442.574, 
5442.624, 5442.824, 5442.424, 5443.224, 5443.274, 5443.474, 5442.924, 
5442.324, 5442.524, 5442.274, 5442.424, 5442.374, 5443.174, 5442.324, 
5442.374, 5442.374, 5442.274, 5442.874, 5443.254, 5442.274, 5442.324, 
5442.324, 5442.974, 5443.074, 5442.374, 5442.474, 5442.424, 5442.274, 
5443.124, 5442.274, 5442.474, 5442.274, 5442.474, 5442.274, 5443.524, 
5443.324, 5442.424, 5443.624, 5443.224, 5443.574, 5442.374, 5442.474, 
5443.424, 5442.424, 5443.374, 5443.274, 5443.174, 5442.324, 5442.374, 
5442.274, 5442.474, 5442.274, 5443.324, 5442.424, 5443.474, 5442.324, 
5442.374, 5442.324, 5443.224, 5442.324, 5442.424, 5442.374, 5442.424, 
5443.374, 5442.424, 5443.274, 5442.424, 5442.424, 5443.174, 5443.874, 
5442.414, 5442.274, 5443.424, 5443.524, 5442.324, 5442.324, 5443.574, 
5442.027, 5442.374, 5443.224, 5443.324, 5442.324, 5442.324, 5442.274, 
5442.027, 5443.474, 5442.274, 5442.374, 5442.374, 5442.374, 5442.374, 
5442.374, 5442.324, 5442.274, 5443.424, 5442.027, 5443.374, 5443.274, 
5442.274, 5442.374, 5442.324, 5443.524, 5442.36, 5442.324, 5443.324, 
5442.324, 5442.274, 5442.274, 5442.324, 5443.374, 5442.027, 5442.324, 
5442.274, 5443.424, 5443.474, 5442.666, 5442.324, 5442.292, 5442.424, 
5442.274, 5442.274, 5442.274, 5442.908, 5442.027, 5442.324, 5442.027, 
5442.274, 5442.274, 5442.183, 5442.274, 5442.274, 5442.274, 5443.149, 
5442.027, 5443.633, 5442.027, 5442.424, 5442.666, 5442.027, 5443.874, 
5442.183, 5443.149, 5443.391, 5442.908, 5442.027, 5443.633, 5443.391
), Conc = c(1165, 1154, 936, 965, 1087, 748, 1081, 1058, 1061, 
968, 1031, 1040, 755, 1019, 631, 997, 842, 947, 975, 691, 990, 
626, 898, 981, 841, 583, 538, 564, 890, 803, 593, 892, 925, 910, 
797, 463, 852, 902, 649, 607, 718, 793, 556, 894, 511, 667, 825, 
871, 361, 429, 350, 440, 537, 359, 806, 753, 558, 833, 510, 806, 
552, 334, 315, 853, 585, 521, 784, 767, 698, 337, 615, 778, 543, 
377, 429, 427, 263, 641, 592, 698, 400, 489, 373, 629, 396, 614, 
211, 200, 196, 312, 298, 258, 198, 368, 399, 302, 326, 417, 547, 
213, 300, 543, 221, 438, 266, 384, 166, 409, 202, 337, 448, 173, 
230, 431, 156, 378, 288, 277, 417, 274, 308, 254, 330, 366, 227, 
331, 366, 131, 232, 333, 192, 257, 238, 330, 281, 203, 293, 236, 
222, 254, 152, 333, 204, 187, 261, 210, 298, 119, 121, 179, 298, 
198, 268, 173, 11, 181, 12, 176, 265, 117, 178, 121, 183, 182, 
297, 13, 171, 166, 239, 287, 117, 181, 194, 235, 162, 197, 243, 
166, 12, 197, 156, 154, 205, 114, 10, 248, 204, 229, 144, 238, 
15, 120, 187, 143, 152, 138, 240, 186, 12, 123, 131, 210, 131, 
8, 144, 210, 186, 14, 185, 135, 183, 150, 120, 111, 123, 121, 
157, 192, 184, 148, 113, 110, 183, 116, 183, 97, 144, 129, 128, 
177, 12, 113, 106, 11, 171, 113, 146, 93, 164, 138, 110, 150, 
156, 168, 59, 144, 146, 109, 132, 14, 151, 117, 11, 148, 88, 
114, 82, 85, 153, 106, 73, 69, 89, 100, 108, 105, 149, 5, 93, 
102, 13, 128, 86, 105, 97, 136, 113, 124, 125, 105, 136, 74, 
111, 51, 78, 121, 119, 19, 57, 82, 72, 50, 99, 61, 77, 124, 56, 
122, 11, 122, 81, 64, 11, 124, 74, 105, 80, 104, 85, 119, 73, 
106, 72, 100, 51, 76, 69, 76, 72, 50, 90, 10, 51, 105, 104, 41, 
77, 97, 41, 85, 11, 96, 97, 65, 7, 95, 75, 39, 97, 37, 89, 84, 
85, 98, 50, 12, 50, 83, 94, 85, 85, 11, 7, 87, 83, 84, 35, 95, 
6, 51, 67, 82, 75, 39, 70, 65, 37, 29, 83, 2, 98, 73, 70, 53, 
71, 73, 33, 19, 58, 73, 27, 66, 10, 29, 66, 69, 66, 12, 42, 21, 
3, 17, 56, 61, 73, 63, 24, 49, 53, 14, 11, 55, 62, 11, 61, 28, 
28, 37, 12, 80, 27, 13, 49, 18, 30, 49, 30, 17, 56, 46, 49, 8, 
12, 25, 52, 39, 83, 47, 13, 10, 9, 9, 37, 37, 4, 20, 80, 52, 
13, 37, 19, 40, 21, 43, 44, 22, 10, 46, 16, 24, 21, 49, 34, 11, 
13, 44, 33, 11, 55, 28, 28, 27, 3, 19, 18, 28, 33, 6, 12, 2, 
12, 35, 14, 22, 26, 17, 61, 11, 5, 23, 24, 2, 14, 17, 13, 13, 
62, 23, 11, 22, 24, 1, 5, 20, 16, 8, 12, 14, 65, 8, 37, 19, 9, 
13, 16, 10, 29, 9, 15, 9, 19, 17, 14, 16, 2, 11, 13, 11, 12, 
23, 20, 17, 11, 8, 32, 13, 10, 13, 14, 9, 10, 12, 37, 7, 15, 
11, 44, 8, 12, 8, 11, 11, 10, 44, 12, 10, 12, 46, 13, 9, 8, 8, 
7, 2, 8, 10, 10, 5, 9, 42, 2, 8, 8, 28, 10, 15, 7, 10, 6, 23, 
7, 19, 12, 7, 7, 8, 28, 32, 22, 5, 33, 7, 8, 12, 5, 13, 6, 9, 
8, 3, 9, 5, 6, 11, 5, 6, 6, 5, 7, 5, 7, 6, 6, 13, 17, 3, 4, 10, 
9, 7, 4, 15, 24, 18, 10, 4, 28, 10, 11, 15, 5, 11, 2, 5, 4, 5, 
5, 3, 5, 4, 7, 3, 5, 2, 0, 1, 4, 18, 1, 3, 5, 5, 12, 7, 13, 11, 
3, 4, 4, 3, 10, 5, 0, 2, 5, 6, 3, 8, 3, 10, 5, 2, 11, 3, 2, 9, 
3, 1, 7, 3, 1, 9, 9, 9, 3, 12, 4, 8, 4, 2, 8, 1, 4, 3, 1, 2, 
9, 6, 2, 10, 6, 5, 2, 1, 4, 1, 7, 8, 4, 3, 3, 7, 5, 2, 14, 2, 
3, 11, 2, 2, 3, 7, 10, 7, 10, 15, 3, 9, 1, 2, 9, 9, 8, 7, 1, 
6, 4, 0, 6, 7, 2, 6, 6, 2, 2, 1, 4, 2, 8, 2, 1, 6, 7, 8, 6, 5, 
1, 7, 1, 2, 3, 2, 2, 5, 7, 6, 2, 6, 1, 3, 1, 2, 6, 2, 3, 0, 6, 
2, 3, 3, 8, 5, 2, 6, 7, 4, 5, 2, 5, 1, 1, 3, 2, 1, 8, 2, 6, 6, 
5, 4, 2, 1, 1, 1, 4, 4, 4, 3, 6, 4, 5, 1, 1, 0, 4, 1, 3, 1, 4, 
1, 5, 2, 0, 1, 0, 3, 2, 0, 3, 2, 3, 3, 1, 0, 5, 8, 8, 7, 2, 2, 
3, 2, 0, 3, 1, 0, 4, 1, 3, 3, 5, 1, 1, 5, 1, 6, 2, 2, 0, 0, 4, 
1, 1, 3, 0, 4, 2, 0, 0, 1, 4, 0, 1, 0, 3, 4, 1, 3, 2, 0, 1, 0, 
5, 3, 0, 2, 6, 3, 5, 1, 0, 0, 4, 1, 1, 0, 1, 0, 1, 0, 1, 0, 5, 
4, 3, 4, 1, 3, 0, 1, 0, 4, 1, 0, 1, 3, 4, 1, 7, 0, 2, 1, 4, 0, 
0, 0, 3, 2, 5, 3, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 4, 0, 1, 
2, 0, 2, 2, 4, 0, 0, 0, 0, 2, 0, 6, 1, 1, 4, 1, 0, 0, 3, 1, 2, 
1, 0, 0, 0, 2, 0, 1, 1, 3, 3, 3, 1, 1, 0, 0, 0, 1, 0, 0, 0, 0, 
0, 1, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 2, 0, 1, 0, 0, 0, 3, 0, 1, 
1, 0, 2, 2, 0, 0, 2, 0, 1, 0, 1, 3, 1, 1, 0, 0, 1, 0, 0, 0, 0, 
2, 1, 0, 1, 0, 1, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 2, 1, 0, 
0, 0, 0, 0, 0, 0, 1, 0, 0, 2, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 
1, 1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 0, 1, 
0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 
1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)), row.names = c(NA, -1177L), class = c("tbl_df", 
"tbl", "data.frame"))

From my understanding the geom_* functions you tried don't work well because your data is an irregular grid. If we make a scatter plot of your data we can see that.

library(ggplot2)

# dat is from your question.
ggplot(
    data = dat,
    aes(x = X_km, y = Y_km, color = Conc)
) + 
    geom_point()

From the geom_contour_filled docs:

These functions require regular data, where the x and y coordinates form an equally spaced grid, and each combination of x and y appears once.

One way to get around that is by interpolating the empty space. I found a way from this question. It uses the akima package: docs.

# interpolate the empty space. results in 100x100 grid.
interp_dat <- akima::interp(
    x = dat$X_km, 
    y = dat$Y_km, 
    z = dat$Conc, 
    nx = 100, ny = 100
)

# convert back to a format ggplot likes
interp_dat <- data.frame(
    x = rep(interp_dat$x, ncol(interp_dat$z)), 
    y = rep(interp_dat$y, each = nrow(interp_dat$z)), 
    z = as.numeric(interp_dat$z)
)

ggplot(
    interp_dat,
    aes(x = x, y = y)
) + 
    geom_contour_filled(aes(z = z))
    # geom_raster(aes(fill = z), interpolate = TRUE) # use this instead for a continuous scale