How do I bring the Z axis on survey dwgs to zero

So I have this drawing which has the z axis all over the place.. I believe there is a command that can be used to bring and flatten the entire drawing down to zero Z height, so I can get on with proper 2d interrogation of the drawing.. Kindly assist.

Different methods to flatten entities with varying Z-coordinates to Z=0.

Via a macro (Source: CADforum)

Add a new macro (icon) to your toolbar - in fact two single-line macros (tool buttons) - one for selected objects and the second for all objects:

[FlattenSel]

[b][font=Arial]^C^C_UCS;;_select \_move _p;;0,0,1e99;;_move _p;;0,0,-1e99;;[/font][/b]

[FlattenAll]

[b][font=Arial]^C^C_UCS;;_move_all;;0,0,1e99;;_move_all;;0,0,-1e99;;_chprop;_all;;_thickness;0;;[/font][/b]

(keep the macro text on a single line; the displayed format is to be used for old MNU/MNS files - if you add the macro through the new CUI dialog, use just its code starting with ^C)

Do not use it on 3D solids as it may distort them.

(original concept by Randy Richardson)

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Using FLATTEN.LSP as originally written by Mark Middlebrook with improvements by Vladmir Livshiz.

FLATTEN.LSP sets the Z-coordinates of these types of objects to 0

;;; in the World Coordinate System:

;;; "3DFACE" "ARC" "ATTDEF" "CIRCLE" "DIMENSION"

;;; "ELLIPSE" "HATCH" "INSERT" "LINE" "LWPOLYLINE"

;;; "MTEXT" "POINT" "POLYLINE" "SOLID" "TEXT"

Link: www.spaug.org/Public_Files/AutoLISP/Flatten.Lsp

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In full AutoCAD one can go to Express Tools and use the FLATTEN OBJECTS command which can be found in the Modify section.

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Some users have suggested using the FLATSHOT command available in full AutoCAD.

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And an “oldie but goodie” from “back in the day” is the CHANGE command and its ELEVATION option.

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Two additional options, in the form of lisp routines, have recently come to my attention.

The first is called Flat.lsp (author: unknown) and the second is called Zero.lsp (author: Allen Cullen as submitted to CADTutor on 23-May-2007). Both can be accessed via this link:

http://www.cadtutor.net/forum/showthread.php?13763-How-to-flatten-the-z&highlight=Extremecheese.....