The generator matrix

 1  1  1  1  1  1  1  1  1  X
 0  X  0  0  X  0  X  X 2X  X
 0  0  X  0 2X  X 2X  X 2X  0
 0  0  0  X 2X 2X  0 2X 2X  X

generates a code of length 10 over Z3[X]/(X^2) who´s minimum homogenous weight is 18.

Homogenous weight enumerator: w(x)=1x^0+114x^18+108x^21+20x^27

The gray image is a linear code over GF(3) with n=30, k=5 and d=18.
As d=18 is an upper bound for linear (30,5,3)-codes, this code is optimal over Z3[X]/(X^2) for dimension 5.
This code was found by Heurico 1.16 in 0.000401 seconds.