PUBLICATIONS--Policy on Publishing Constituents with Both Field and Laboratory Values 

In Reply Refer To:                       January 22, 1982
EGS-Mail Stop 412


Subject: PUBLICATIONS--Policy on Publishing Constituents 
         with Both Field and Laboratory Values

Quality of Water Branch Technical Memorandum No. 81.04 
assigned WATSTORE parameter codes to laboratory measurements 
of pH, specific conductance, and alkalinity. In addition, 
codes were assigned for hydroxide, carbonate, bicarbonate, 
and carbonate alkalinity measurements by incremental 
titration and fixed-pH endpoint titration in the field and 

Several questions have been raised recently as to the policy 
on publication and storage of these data. The purpose of this 
memorandum is to provide such policy guidance.

Some background information may help explain the guidelines 
given below. Parameter codes were assigned to laboratory 
values of pH, specific conductance, and alkalinity so that 
both field and laboratory values could be stored without 
ambiguity as to source. Until this action was taken, 
laboratory measurements could be, and often were, substituted 
under the same parameter code for questionable field values 
in publications and data storage. As was stated in Quality of 
Water Branch Technical Memorandum 73.02, the U.S. Geological 
Survey considers the field value to be the better of the two 
since changes in these characteristics can occur in transit 
to the laboratory. Substituting laboratory values for field 
values both obscures the source of the data and incurs the 
risk that one incorrect value will be replaced by another. 
The only unambiguous action that can be taken when both 
laboratory and field values are available for the same 
measurement is to store both under separate parameter codes.

After the decision was made to store both field and 
laboratory values, appropriate STORET parameter codes were 
sought. In this exercise we encountered some conflicts. In 
particular, STORET code 00094, Specific Conductance, Field, 
seemed to be the appropriate code under which to store field 
specific conductance values. Historically, however, the 
Geological Survey has stored the "best value," based on the 
judgement of the observer, under code 00095, Specific 
Conductance, per STORET instructions. Because of this 
practice the file contains both laboratory and field values 
stored under this code. It would be impractical and extremely 
confusing to both ourselves and EPA to separate the huge 
number of field and laboratory values now stored under code 
00095 and restore the field value under 00094. But it was 
clear that the practice of substituting a laboratory value 
for a questionable field value should cease.

Therefore, it was desided to create a 90000-series code 
(90095) for laboratory specific conductance and continue to 
use code OOO95 for storage of field values. Since the title 
for STORET code 00095 does not explicitly state field or 
laboratory and, by accepted EPA usage, this code has been 
assumed to represent "best value," its use by the Geological 
Survey conforms to EPA's intent.

Codes for both field and laboratory pH were available in 
STORET and they did not conflict with present usage. Thus, 
use of code 00400 continues for field pH and 00403 for 
laboratory pH.

In the case of alkalinity, no STORET code specifying 
laboratory analysis existed and again, a 90000-series code 
(90410) was assigned.

As directed in Quality of Water 8ranch Technical Memorandum 
80.27, after October 1, 1980, the incremental titration 
method of Barnes (1964), a new description of which was 
transmitted under Quality of Water Branch Technical 
Memorandum 82.05, is the only acceptable method for 
determination of the individual chemical species carbonate 
and bicarbonate. This policy was intended to stop the use of 
the fixed-pH endpoint method for all carbonate species-
related measurements except alkalinity (00410 or 90410), 
which continues to be measured by acid titration to pH 4.5. 
It was also intended that the values of the measurements 
discussed that were in storage before October 1, 1980, 
eventually be identified as to method and source (field or 
lab) and be reassigned to parameter codes identifying both 
method and source. Quality of Water Branch Technical 
Memorandum 81.04 assigned parameter codes for this purpose.

To avoid a great deal of work and expense that would be 
involved in reassigning codes for hydroxide, carbonate, 
bicarbonate, and carbonate alkalinity to existing data in the 
historic file, the old codes, namely 71830, 00445, 00440 and 
00430 were retained but were identified as field 
determinations by the fixed-pH endpoint method. Except in 
rare cases, no data were to be entered under these codes 
after October 1, 1980. Values obtained by the accepted method 
(incremental titration in the field) are to be entered under 
codes 99830, 99445, 99440 and 99430 until acceptable new 
STORET codes can be obtained from EPA. In addition, 90000-
series codes were assigned to hold values from the historic 
record obtained in laboratories by either the incremental 
titration method or the fixed-pH endpoint method. No current 
data should be stored under these codes because the National 
Water Quality Laboratories stopped measuring these 
constituents in 1978. The intention here was that districts 
could identify historic data stored under the old codes that 
had been obtained by methods other than fixed-pH endpoint in 
the field and shift those data to one of the appropriate new 
90000-series codes.

The guidelines on publication given here are based on our 
belief that the field measurements of pH, specific 
conductance, alkalinity, hydroxide, carbonate, bicarbonate, 
and carbonate alkalinity, when done correctly, are the best 
measurements available and should be given priority in 
publication and transferral to the STORET data base.

Guidelines for publication and storage are as follows:

1. Under no circumstances will laboratory values be 
substituted for field values or vice versa in either the data 
files or data publications.

2. When both field and laboratory values are available, the 
field value will be published in preference to the laboratory 
value unless there is reason to suspect the quality of the 
field measurement.

3. When the field value is unavailable or questionable, the 
laboratory value may be published.

4. Only values of hydroxide, carbonate, bicarbonate, and 
carbonate alkalinity obtained in the field by the incremental 
titration method will be published. Rare exceptions have been 
allowed by written permission of the Assistant Chief 
Hydrologist for Research and Technical Coordination for 
projects locked into the field fixed-pH endpoint method. 
These values may be published in a column suitably labeled 
"field, fixed-pH endpoint." Transferral of these data to 
STORET must await appropriate STORET codes from EPA. Note 
that publication and storage of alkalinity measurements in 
the field (00410) and laboratory (90410) are governed by 
guidelines 1, 2, and 3.

To assist in the WY 1981 data reports, the column headings 
from the tabling program for codes 90095, 90410 and 00403 
have been made to read "laboratory"; headings for codes 
99830, 99445, 99440 and 99430 have been made to read "field, 
incremental titration."

                         R. J. Pickering
                         Chief, Quality of Water Branch

This memorandum supersedes Quality of Water Branch Technical 
Memorandum 73.02 and supplements Quality of Water Branch 
Technical Memorandums 80.27 and 81.04.

Key words: water quality, publications, publication policy, 
           WATSTORE, parameter codes

WRD Distribution: A, B, S, FO, PO