public double ContourInterval {get; set;}

{
  var contourDef = new TinContourRendererDefinition();

  // now customize with a symbol
  contourDef.Label = "Contours";
  contourDef.SymbolTemplate = contourLineSymbol.MakeSymbolReference();
  contourDef.ContourInterval = 6;

  contourDef.IndexLabel = "Index Contours";
  contourDef.IndexSymbolTemplate = indexLineSymbol.MakeSymbolReference();
  contourDef.ContourFactor = 4;
  contourDef.ReferenceHeight = 7;
  // Note: Needs QueuedTask to run
  {
    if (surfaceLayer.CanCreateRenderer(contourDef))
    {
      CIMTinRenderer renderer = surfaceLayer.CreateRenderer(contourDef);
      if (surfaceLayer.CanSetRenderer(renderer, SurfaceRendererTarget.Contours))
        surfaceLayer.SetRenderer(renderer, SurfaceRendererTarget.Contours);
    }
  }
}