G ra b S a m p le
G ra b S a m p le
M aterials that cause turbidity tend to be evenly
E q uip m ent
distributed in the w ater colum n and across the T he follow ing equipm ent w ill be needed to sam ple
stream cross-section. T herefore a “ grab sam ple” turbidity:
sufficiently represents the sam ple location. T he • sam ple can be collected at any point in the stream
A portable turbidimeter (available from D E Q ’s (either near the bank or the deepest part of the
V olunteer M onitoring Program or scientific channel) by low ering the lip of the sam ple bottle
supply houses). T hese instrum ents are below the surface of the w ater. calibrated on the nephlom etric turbidity m ethod
(see above) and m eets the criteria established
S a m p le T im ing
by E PA . T he H A C H 2100P (portable) T urbidim eter is available to local w atershed
T im ing of the grab sam ple is just as critical as site groups through D E Q ’s V olunteer M onitoring
selection. Stream flow greatly influences turbidity. Program and is referenced in this protocol. T he
T herefore, it is im portant to sam ple for turbidity
H A C H T urbidim eter kit includes the G elex during sim ilar flow conditions unless the objective Secondary Standards (for checking the
is to m onitor the differences betw een low flow and accuracy of the turbidim eter in the field), and
peak flow turbidity. For exam ple, it w ould be sm all sam ple bottles for testing turbidity w ith
inappropriate to com pare a pre-project sam ple the turbidim eter.
collected during a storm event w ith a post-project sam ple that w as collected during low er flow
• Stabilized Formazin Primary Standard K it conditions. G iven the above discussion regarding
(available from the D E Q V olunteer M onitoring site selection and sam ple tim ing, consider the Program ) for a m ore thorough, periodic,
follow ing guidelines w hen designing a sam ple: turbidim eter calibration. (see the “ C alibration”
C learly define the project objectives and •
section below )
A ny clean container for taking grab samples. m onitoring questions. T his w ill help identify sam pling location and tim ing.
C learly identify the source, project, or activity being m onitored and locate sam ple points to the Site selection procedures described in C hapter 3
S ite S electio n
closest proxim ity of these activities. (Selecting Sites) apply to turbidity m onitoring. A ll w ater quality sam ples collected to m easure
D escription of sampling point conditions of concern and consistently m onitor during those tim es and conditions.
C learly identify the time period or flow
• Identification (or L at/L ong.) of sampling site •
• D ate and time of collection If the objective is to monitor a specific activity,
then obtain turbidity sam ples upstream of the
• N ame of collector
project site during the activity as a control to m onitor background turbidity conditions.
C alibration
T hese sam ples should be collected in addition T he M odel 2100P T urbidim eter is calibrated w ith to the sam ples obtained im m ediately Form azin Prim ary Standard at the factory and does dow nstream of the project site. n o t req u ire re c a lib ra tio n b e fo re u se . W ith steady
• If the objective is to collect baseline data on field use, how ever, the H A C H C om pany turbidity, the sam ple frequency and num ber of
recom m ends recalibration every three m onths, or as locations m ust be large enough to capture the
often as experience dictates. R efer to the range of flow conditions and turbidity-
Instrum ent M anual for com plete instructions. generating activities that are occurring in the reach or basin.
F ield T urb id ity M ea surem ent P ro ced ure.
A ccuracy C heck Field check the turbidim eter against the G elex
D ata collection can begin after follow ing the Secondary Standards at the start of each set of
procedures described above for instrum ent m easurem ents. If num erous sam ples are to be
preparation and site selection. processed, periodically check the instrum ent against
the calibration standards and adjust accordingly.
1. C ollect a representative sam ple in a clean container. Fill one of the sam ple bottles
• Place the first G elex Standard (0 to 10 (included w ith the turbidim eter kit) to the line
range) in the cell com partm ent of the m eter (approx. 15-m l), taking care to handle the w ith the w hite diam ond on the vial
sam ple bottle by the top to avoid fingerprints aligning w ith the orientation m ark on the
and dirt on the bottle. C ap the bottle. m eter. C lose the lid.
• 2. W ipe the bottle w ith a soft, lint-free cloth to Press “ P O W E R ” , and w hen 0.00 show s
rem ove w ater spots and fingerprints. in the display w indow , press “ R E A D .” If
the reading is not w ithin 5% of the
3. Press the “ I/O ” button to turn the instrum ent Standard, recalibrate the instrum ent w ith
on. Place the instrum ent on a flat, steady the prim ary Form azin Standard (see
surface.
4. Put the sam ple bottle in the instrum ent cell • com partm ent so the diam ond m ark on the bottle R epeat this procedure w ith the remaining
below ).
tw o G elex Standards (0 to 100 and 01 to aligns w ith the orientation m ark on the 1000 ranges).
instrum ent.
5. Select the m anual or autom atic range by pressing the “ R A N G E ” key. “ A U T O R N G ”
D uplicate Sam ples is recom m ended and w ill be displayed. Press O btaining duplicate sam ples is im portant for
“ R E A D .” T he display w ill show “ -------
docum enting the variability from sam ple to sam ple. N T U ” then the turbidity reading in N T U .
D uplicate sam ples should be collected at a rate of R ecord the turbidity after the lam p sym bol one duplicate sam ple for every ten regular sam ples
turns off.
collected. A ll sam ples m ust be identified on a field N otes: on taking M easurem ents data sheet by:
• the G overnor’s W atershed E nhancem ent B oard A lw ays cap the sample bottle to prevent
spillage of sam ple w ater into the instrum ent. •
A lw ays place the instrument on a level,
T urb id ity D a ta A na ly sis
stationary surface. O nce the data has been stored on a com puter and on
A lw ays close the cell compartment lid during backup disks, data analyses can begin. A nalysis of m easurem ent and storage.
turbidity data depends on the specific objectives. •
D o not leave the sample bottle in the cell com partm ent for long periods of tim e.
Project M onitoring If the collected data w ill be used to determ ine
A lw ays use clean sample bottles. w hether m anagem ent activities are increasing •
A void operating instrument in direct sunlight. turbidities above a given level, then the follow ing • inform ation should be included:
M ake sure that a cold w ater sample does not fog the sam ple bottle.
• Information on the activity or project. •
A void allow ing the w ater sample’s contents to • T urbidity data upstream and dow nstream of the settle prior to taking a turbidity m easurem ent.
activity, and, depending on the objectives, •
A lw ays take turbidity measurements w ithin possibly w ithin the reach affected by the
24 hours of collecting the sam ples.
activity.
C ollecting data at these same locations before
A perm anent record of each sam pling event should the activity starts is also advisable.
be m aintained and should include: • Significant observations related to the sample
W ith this inform ation, an investigation of trends • betw een turbidity and the m anagem ent activity can
O ther ancillary environmental measurements
begin.
(see below ) • W eather and other physical conditions
R ela tio nship s b etw een turb id ity a nd o ther
• strea m cha ra cteristics. Sample date
• Sample ID
Suspended Sedim ent
A ncilla ry D a ta
If the turbidity data w ill be used to determ ine suspended sedim ent characteristics, the relationship
O nce a site is selected, other im portant descriptive betw een suspended sedim ent and turbidity for the inform ation should be recorded such as general
particular sites m ust be established. C ontact the flow conditions and depths, and references to
m entor for specific sam pling procedures that m ust landm arks such as tributary nam es, river m ile,
be follow ed for suspended sedim ent. roads, and bridges. T he latitude and longitude of
the site is an im portant piece of inform ation that can
be obtained from a topographic m ap or from a
Stream flow Stream flow inform ation can be collected at the
global position device (G PS). sam e sites as the turbidity data. M onitors should
investigate the relationships betw een increases and Inform ation about the landow ner and contacts decreases in stream flow and turbidity. T he O regon (telephone, address, E -m ail) should be recorded.
W ater R esources D epartm ent is developing a
D o c u m en t a la n d o w n e r’ s g ra n te d p e rm issio n fo r protocol for m easuring stream flow . C ontact a
a c c e ss to p riva te la n d s.
A photograph of the m onitoring site can be useful turbidity m entor for m ore inform ation on this. for locating equipm ent. G uidance for photo
docum entation of m onitoring sites is provided by
N o rth w e st a n d A la sk a . E PA region 10, 910/9-91-
R eferences
001. 166 pp. Stednick, J.D . 1991. W ildland water quality
B eschta, R .L ., Jackson, W .L . 1980. T urbidity and
A cadem ic Press, Inc., San suspended sedim ent relationship. P 271-282 in
sa m p lin g a n d a n a ly sis.
D iego, C A .
P ro c e e d in g s, sym p o siu m o n W a tersh e d T he project coordinator is directed also to the E PA m a n a g e m en t . A m er. Soc. O f C iv. E ngineers.
V olunteer M onitor’s G uide to Q uality A ssurance
B row n, G . 1983. Forestry and water quality.
Project Plans (E PA 1996).
O SU B ookstores Inc., C orvallis, O R . 142 pp. M acdonald, L H ., Sm art, A .W ., and W issm ar, R .C .
1991. M onitoring guidelines to evaluate effects of fo restry a ctivities o n strea m s in th e P a cific