Creating a new lake in a DTM

[Lynda]

I have an esxisting site with contours and have created both existing and proposed DTMs. I now need to add a small lake and balancing ponds for a SUDS drainages system.I have tried creating new contours (from polyline) with a fence around all on a separate pond layer but my proposed DTM will not update.

It sees the layer as having a fence but ignores the contours.

I have tried putting the new contours on to the MOD site DTM data layer but this updates the existing DTM only - which I don't want to do at all.

I've tryed using a pad with gradient but this is only planar. Can pads be set one inside the other to create a pond that gets deeper into the centre?

How can I get the update DTM to see my new contours or is there another way of creating a lake. I want to be able to calculate cut and fill.

Thanks in anticipation.

[islandmon]

"I have tried creating new contours (from polyline) with a fence around all on a separate pond layer but my proposed DTM will not update."

The DTM Method requires a '3d Polygon' (NOT a polyline or Extrude ) set to the correct Z height above the 'Existing Datum " 00' " Elevation ' and a 2d Plygon Fence ( non conflicting ).

[Lynda]

Thanks for this very prompt reply. I have just managed to solve the problem by converting my polylines to 3d polygons and moving them to the Site -DTM-Modifier class. I'd omitted to move my converted contours to this class previously and think that this is why they were overlooked. I had already made them into 3D polygons by using the 2d polys to 3d contour tool. Does this not work with polylines?

Always helps when I write the problem down!