It is checked numerically that the uncertainty in the final injection front position due to uncertainty in the choice of the method of the injection front interpolation on every time layer can be neglected in the estimation of the truncation error of the calculation of this position in the framework of the real scale grouting model. Results of numerical experiments indicate that the curvilinear grid this calculation is performed on has chaotic dispositions of its nodes in space on some time layers and that it does not give rise to significant final injection front position distortion.