1. A. Using all the available background data (n_b readings), calculate the background mean (x_b) and background variance S_b². For the single monitoring well under investigation (n_m reading), calculate the monitoring mean (x_m) and monitoring variance S_m². For any set of data (x₁, x₂ ...x_n), the mean is calculated by: and the variance is calculated by: where “n” denotes the number of observations in the set of data.

   

   

2. B. The t-test uses these data summary measures to calculate a t-static (t*) and a comparison t-statistic (t_c). The t* value is compared to the t_c value and a conclusion reached as to whether there has been a statistically significant change in any indicator parameter.

3. C. The t-statistic for all parameters except pH and similar monitoring parameters is:

   

4. D. If the value of this t-statistic is negative then there is no significant difference between the monitoring data and background data. It should be noted that significantly small negative values may be indicative of a failure of the assumption made for test validity or errors have been made in collecting the background data.
5. E. The t-statistic (t_c) against which t* will be compared, necessitates finding t_B and t_m from standard (one-tailed) tables where, t_B= t-tables with (t_B^-1) degrees of freedom, at the 0.05 level of significance.
6. F. t_m = t-tables with (n_m^-1)degrees of freedom, at the 0.05 level of significance.

7. G. Finally, the special weighting W_B and W_M are defined as: and so the comparison t-statistic is:

   

   

8. H. The t-statistic (t*) is now compared with the comparison t-statistic (t_c) using the following decision-rule:

   1. (1) If t* is equal to or larger than t_c, then conclude that there most likely has been a significant increase in this specific parameter;
   2. (2) If t* is less than t_c, then conclude that most likely there has not been a change in this specific parameter.
9. I. The t-statistic for testing pH and similar monitoring parameters is constructed in the same manner as previously described except the negative sign (if any) is discarded and the caveat concerning the negative value is ignored. The standard (two-tailed) tables are used in the construction t_c for pH and similar monitoring parameters.
10. J. If t* is equal or larger than t_c, then conclude that there most likely has been a significant increase (if the initial t* had been negative, this would imply a significant decrease). If t* is less than t_c, then conclude that there most likely has been no change.

11. K. A further discussion of the test may be found in Statistical Methods (6th Edition, Section 4.14) by G.W. Snedecor and W.G. Cochran, or Principles and Procedures of Statistics (1st Edition, Section 5.8) by R.G.D. Steel and J.H. Torrie.

    Standard t-Tables 0.05 Level of Significance
    Degrees of Freedom	t-values (one-tail)	t-values (two-tail)
    1	6.314	12.708
    2	2.920	4.303
    3	2.353	3.182
    4	2.132	2.776
    5	2.015	2.571
    6	1.943	2.447
    7	1.895	2.365
    8	1.860	2.306
    9	1.833	2.262
    10	1.812	2.228
    11	1.796	2.201
    12	1.782	2.179
    13	1.771	2.160
    14	1.761	2.145
    15	1.753	2.131
    16	1.746	2.120
    17	1.740	2.110
    18	1.734	2.101
    19	1.729	2.093
    20	1.725	2.086
    23	1.714	2.069
    24	1.711	2.064
    25	1.708	2.060
    30	1.697	2.042
    40	1.684	2.021

Authority: Environment Article, Title 7, Subtitle 2, Annotated Code of Maryland

Effective date:

Regulations .01—.18 adopted as an emergency provision effective November 18, 1980 (7:25 Md. R. S-1); adopted permanently effective April 3, 1981 (8:7 Md. R. 642)

Regulations .01, .05G, .06, .08A, .11C, .12D, and .14C amended effective January 18, 1982 (9:1 Md. R. 20)

Regulations .01—.12, .18 amended effective January 31, 1983 (10:2 Md. R. 110)

Regulations .01A, B, .02F, .05D, H, .07C, D, G, H, .08A, .09G, .10D, F, .11A-1, C, E—G, .12A, B, D, D-1, E, G, .13, .14, .15A, .16A, .18 (Appendix IV) amended, .15-1 adopted, .06 repealed and new .06adopted, .10I, .12C-1, and .18 (Appendices VI—XIII) repealed effective February 13, 1984 (11:3 Md. R. 202)

Regulations .01A, .02D, F, .05G, .06A, I, .07A, D, I, .10D, .11B, F, F-1, .12D-1, .14A—C, J, L, .15-1A, D amended, and .01C adopted effective July 30, 1984 (11:15 Md. R. 1330)

Regulation .01A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .02I, J adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .04G amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .05A, D amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .06A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .06L adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .07B amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .07C—J repealed and new C—J adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .08A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .09F, H, and I amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .10D, E amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .10I adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .11A-1, B, C, E, F, F-1 amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .12B, D-1 amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .12H adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .13N adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .14B, C amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .14P adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .15A amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .15-1B, C, and F amended effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .16G adopted effective April 18, 1988 (15:8 Md. R. 1009)

Regulation .10C-1—I recodified to .10D—J

Regulation .11A-1—F recodified to .11B—G

Regulation .11F-1—I recodified to .11H—K

Regulation .12D-1 and D-2 recodified to .12E and F

Regulation .12E—H recodified to .12G—J

Regulation .15-1 recodified to Regulation .16

Regulations .16—.18 recodified to Regulations .17—.19

Appendix I—Appendix V codified as Regulations .20—.24

Chapter recodified from COMAR 10.51.05 to COMAR 26.13.05

Regulation .01A amended effective May 24, 1993 (20:10 Md. R. 853)

Regulation .01C amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .02D amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .02F amended effective April 1, 1991 (18:6 Md. R. 690); May 24, 1993 (20:10 Md. R. 853)

Regulation .04G amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .05B amended effective May 24, 1993 (20:10 Md. R. 853)

Regulation .05D amended effective April 1, 1991 (18:6 Md. R. 690); December 23, 1991 (18:25 Md. R. 2759); May 24, 1993 (20:10 Md. R. 853)

Regulation .05F amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .06A amended effective April 1, 1991 (18:6 Md. R. 690)

Regulation .06K amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .07A, E, and F amended effective May 24, 1993 (20:10 Md. R. 853)

Regulation .07B, C, E, G, and H amended effective April 1, 1991 (18:6 Md. R. 690)

Regulation .07B, F amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .08A amended effective April 1, 1991 (18:6 Md. R. 690)

Regulation .08B amended effective November 9, 1992 (19:22 Md. R. 1991)

Regulation .10 repealed and new Regulations .10—10-7 adopted effective May 24, 1993 (20:10 Md. R. 853)

Regulation .10G amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .11D amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .14B, N amended effective December 23, 1991 (18:25 Md. R. 2759)

Regulation .16-1 adopted effective April 1, 1991 (18:6 Md. R. 690) (Regulation .16-1 was initially adopted as Regulation .17. The recodification to Regulation .16-1 negated the need for some changes to cross-references shown in the Maryland Register.)

Regulation .20A amended effective December 23, 1991 (18:25 Md. R. 2759)

Chapter revised effective April 11, 1994 (21:7 Md. R. 533)

Regulation .01A amended effective August 28, 1995 (22:17 Md. R. 1321)

Regulation .01 amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .05F, H amended effective May 5, 1997 (24:9 Md. R. 659)

Regulation .07D amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .08A amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .08B amended effective August 28, 1995 (22:17 Md. R. 1321)

Regulation .10A amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .14N amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .16A, F amended effective May 8, 1995 (22:9 Md. R. 648)

Regulation .16D amended effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-1 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-2 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-3 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .17-4 adopted effective September 10, 1997 (24:5 Md. R. 413)

Regulation .21 repealed effective May 5, 1997 (24:9 Md. R. 659)

Chapter revised effective October 16, 2000 (27:20 Md. R. 1843)

Regulation .01A amended effective November 1, 2002 (29:21 Md. R. 1647); May 1, 2008 (35:8 Md. R. 809); May 3, 2021 (48:9 Md. R. 359); January 13, 2022 (49:1 Md. R. 14); October 1, 2025 (52:17 Md. R. 876)

Regulation .01D amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .02C amended effective November 1, 2002 (29:21 Md. R. 1647)

Regulation .02C, D amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .02-1 recodified from COMAR 26.13.06.01 effective October 16, 2000 (27:20 Md. R. 1843)

Regulation .02-2 adopted effective January 13, 2022 (49:1 Md. R. 14)

Regulation .03E, G amended effective May 3, 2021 (48:9 Md. R. 359)

Regulation .04G amended effective May 1, 2008 (35:8 Md. R. 809); October 1, 2025 (52:17 Md. R. 876)

Regulation .05 amended effective September 11, 2006 (33:18 Md. R. 1507)

Regulation .05A, C amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .05B amended effective November 1, 2002 (29:21 Md. R. 1647); January 13, 2022 (49:1 Md. R. 14)

Regulation .05B, F amended effective May 3, 2021 (48:9 Md. R. 359)

Regulation .05C, D amended effective January 13, 2022 (49:1 Md. R. 14); October 1, 2025 (52:17 Md. R. 876)

Regulation .07 amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .08B amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .11 amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .12 amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .13L amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .14 amended effective January 13, 2022 (49:1 Md. R. 14)

Regulation .14N amended effective October 1, 2025 (52:17 Md. R. 876)

Regulation .16F amended effective May 1, 2008 (35:8 Md. R. 809)

Regulation .17-3E amended effective November 1, 2002 (29:21 Md. R. 1647)

Regulation .18 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .18-1 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .18-2 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .18-3 adopted effective May 1, 2008 (35:8 Md. R. 809)

Regulation .21 adopted effective May 1, 2008 (35:8 Md. R. 809)