Measurement equipment and techniques used in studying radionuclide movement in the Columbia river estuary

CHAPTER 28

MEASUREMENT EQUIPMENT AND TECHNIQUES USED IN STUDYING RADIONUCLIDE MOVEMENT IN THE COLUMBIA RIVER ESTUARY

Edmund A. Prych, Research Engineer D. H. Hubbell, Research Hydrologist

J. L. Glenn, Research Geologist

U.S. Geological Survey, lvater Resources Division Portland, Oregon

ABSTRACT

An

investigation of the movement of radionuclides in the

Columbia River estuary is being conducted by the U.S. Geological Survey. The necessity for information on ~.,ater discharge, suspended and bed sediments, and radioactivity prompted the development of new measure-ment techniques and equipment suitable for estuarine conditions.

Flow velocities and directions throughout the entire depth at a single vertical are measured from an unanchored boat in about a minute ~vith the neIY discharge measuring technique and it appears that approxi-mately 20 verticals in cross sections up to 4 miles wide can be measured in 1.5 hours. Measured discharges in an upstream reach of the Columbia River agree fairly IYell ~vi th those measured by conventional methods. In situ measurements of radioactivity sorbed on the bed sediments are obtained IYith a radiation detector that is mounted in an unden.,ater sled. Samples of water and suspended sediment are obtained for radionuclide and sedimentation analyses ~.,ith a high-volume sampler. The samples are sepa-rated ~.,ith a high-flolY membrane filter system for analysis. Core sample S of the bed sediments, IYhich range from silty clay to medium sand, are collected in depths up to about 70 feet and flm., velocities up to about 5 feet per second with a ne~"ly devised portable vibratory sampler.

INTRODUCTION

Since the mid-1940's, the U.S. Atomic Energy Commission has operated nuclear reactors at the Hanford installation near Richland, Hash., approximately 375 river miles upstream from the mouth of the Columbia River. Cooling ~.,ater for the reactors is drawn from the Columbia River, and after treatment and use it is returned to the river. The effluent contains small amounts of activated material that is both in solute and in particulate form. Although much of the radioactivity decays, some is transported by the river to the estuary and then to the ocean.

In 1963, the U.S. Geological Survey, in cooperation ~vith the Atomic Energy Commission, began an investigation of radioactivity in th~ Columbia River estuary. The primary purposes are to study the dispositi.-C>~ of radioactivity in the estuary, the processes involved in the movement C> the activity, and, insofar as possible, the rates of movement of the

activity. This report describes equipment and techniques ~.,hich ~"ere developed especially for this study.

684

COASTAL ENGINEERING

l a o r d e r t o o b t a x n e s s e n t i a l b a s i c d a t a , v a r i o u s h y d r o l o g i e and r a d x o l o g x c measurements a r e r e q u i r e d . I n g e n e r a l , e x i s t i n g equipment and measurement methods were n o t c o m p l e t e l y s a t i s f a c t o r y f o r c o U e c t i n e d a t a m t h e e s t u a r y . T h e p r e d o m i n a n c e o f s a n d and t h e r e l a t i v e l y s t r o L

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''^^'^'^ ''"'^^^ "^^^ a p p l i c a b i l i t y o f o c e a L g r a ^ h i c ' U m i t e d t h t h e t i d e s , s a l i n i t y , and s i z e o f t h e f s t u a r y l i m i t e d t h e a p p l i c a b i l i t y o f r i v e r methods. To overcome t h e s e l i m i t a ! t i o n s , new equipment and t e c h n i q u e s s u i t a b l e f o r u s e i n t h e C o l u m b i a R i v e r e s t u a r y were d e v e l o p e d . T h e s e new d e v e l o p m e n t s i n c l u d e ways f o r ( 1 ) m e a s u r i n g w a t e r d i s c h a r g e r a p i d l y and c o n v e n i e n t l y a t c r o s s s e c t i o n s a l o n g t h e e s t u a r y ; ( 2 ) m o n i t o r i n g r a d i o a c t i v i t y i n t h e s t r e a m b e d ; ( 3 ) c o l l e c t i n g l a r g e s a m p l e s o f w a t e r and s u s p e n d e d s e d i m e n t a t s t r e a m v e l o c i t y ; ( 4 ) s e p a r a t i n g , on b o a r d a b o a t , l a r g e volumes o f w a t e r and s e d i m e n t ; and ( 5 ) c o l l e c t i n g , i n r a p i d l y f l o w i n g w a t e r , 6 - f o o t l o n g c o r e s o f bed m a t e r i a l r a n g i n g from s a n d t o s i l t y c l a y . A H equipment has b e e n s u c c e s s f u l l y u s e d from a 3 7 - f o o t c o m m e r c i a l f i s h i n g boa^

MEASUREMENT OF WATER DISCHARGE

I n f o r m a t i o n on water d i s c h a r g e and i t s i n t e g r a l p a r t s , v e l o c i t y d i s t r i b u t i o n and channel geometry, i s r e q u i r e d f o r a v a r i e t y o f reasons. Water d i s c h a r g e i s r e q u i r e d f o r the q u a n t i t a t i v e d e t e r m i n a t i o n o f t h e t r a n s p o r t o f m a t t e r i n s o l u t i o n o r suspension. Data on v e l o c i t y and

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^ " " ^ " « « « y f o r the s t u d y o f d i f f u s i o n , s a l i n i t y i n -t r u s i o n , bedload -t r a n s p o r -t , and o -t h e r h y d r a u l i c phenomena.

Because o f t i d e s , s a l i n i t y i n t r u s i o n , and n o n u n i f o r m i t y o f chan-n e l geometry, f l o w i chan-n t h e e s t u a r y i s uchan-nsteady achan-nd c u r r e chan-n t p a t t e r chan-n s a r e v e r y complex. Tides a t t h e mouth o f t h e Columbia R i v e r a r e s e m i d i u r n a l w i t h one f l o o d and one ebb t i d e every 12.6 hours. T h e r e f o r e , t o d e f i n e adequately t h e d i s c h a r g e t h r o u g h a cross s e c t i o n i n t h e e s t u a r y a number o t separate complete measurements must be made d u r i n g a t i d a l c y c l e -one measurement every 1.5 hours p r o b a b l y w i l l be adequate. Because'some measurement cross s e c t i o n s a r e as much as 4 m i l e s vri.de and because v e l o c i t i e s must be measured a t a p p r o x i m a t e l y 20 d i f f e r e n t v e r t i c a l s f o r ade-quate d e f i n i t i o n , v e r y l i t t l e t i m e can be spent a t a s i n g l e v e r t i c a l . A l s o because t h e f l u i d d e n s i t y i s nonhomogeneous and f l o w p a t t e r n s a r e complex, complete v e r t i c a l v e l o c i t y p r o f i l e s must be measured.

W i t h t h e t e c h n i q u e d e v i s e d , measurements are made f r o m an unanchored b o a t . Water v e l o c i t i e s r e l a t i v e t o t h e boat and depths a r e measured w i t h a s l i g h t l y m o d i f i e d v e r s i o n o f a v e l o c i t y - a z i m u t h - d e p t h assembly (VADA) (Loclcett and Kidby, 1961; B a r r o n , 1963, p. 1 0 ) . The a b s o l u t e v e l o c i t y o f the boat i s measured tóth a s o n i c n a v i g a t i o n u n i t t h a t I S on board, and t h e l o c a t i o n o f each v e r t i c a l i s determined by o b s e r v i n g w i t h a h y d r o g r a p h i c s e x t a n t two angles between t h r e e k n o ™ p o i n t s .

The VADA u n i t ( p i . l A ) i s an i n s t r u m e n t package c o n s i s t i n g o f a v e l o c i t y meter r i g i d l y mounted above a 140-pound s t r e a m l i n e d brass w e i g h t . The w e i g h t houses a remote-reading magnetic compass f o r measur-i n g t h e o r measur-i e n t a t measur-i o n o f t h e meter, and t h e t r a n s d u c e r o f a s o n measur-i c fathom-e t fathom-e r f o r mfathom-easuring t h fathom-e d i s t a n c fathom-e t o t h fathom-e strfathom-eambfathom-ed. Thfathom-e assfathom-embly i s

RADIONUCLIDE MOVEMENT 6 8 5

suspended from a boom by a 1/4-inch OD, 7-conductor, armored c a b l e . A s w i v e l v;ith s l i p r i n g s l o c a t e d about 1.5 f e e t above t h e weight a l l o w s the u n i t t o r o t a t e i n d e p e n d e n t l y o f t h e c a b l e . The cable i s wound on a d-c m o t o r - d r i v e n r e e l t h a t a l s o i s equipped V7ith s l i p r i n g s .

B a s i c a l l y , t h e v e l o c i t y meter i s an O t t c o s i n e p r o p e l l e r d i r e c t l y coupled t o a 2 4 - t o o t h s t e e l gear. The gear r o t a t e s i n t h e magnetic f i e l d of a v a r i a b l e r e l u c t a n c e p i c k u p causing an a-c s i g n a l t o be generated. The s i g n a l i s t r a n s m i t t e d t h r o u g h t h e suspension c a b l e t o an a m p l i f i e r and t h e n t o a frequency meter w i t h an analog o u t p u t . The o u t p u t i s recorded on a s t r i p - c h a r t r e c o r d e r . A b l o c k diagram o f these and o t h e r components o f t h e f l o v ; measurement system i s g i v e n i n f i g u r e 1.

I n o r d e r t o e s t a b l i s h t h e r e l a t i o n between t h e r a t e o f r o t a t i o n of t h e meter p r o p e l l e r and t h e f l o w v e l o c i t y , the v e l o c i t y meter was c a l i b r a t e d i n a l a b o r a t o r y tov/ing t a n k . For c a l i b r a t i o n , t h e VADA u n i t was suspended by t h e r e g u l a r c a b l e and s l i p - r i n g s w i v e l . To check t h e c o s i n e p r o p e r t y o f t h e O t t meter, t h e angle t h a t t h e u n i t made t ^ i t h t h e h o r i z o n t a l was v a r i e d from 0° t o 45° by changing t h e o r i e n t a t i o n o f t h e w e i g h t by means o f a r o d f a s t e n e d t o t h e t a i l . The c a l i b r a t i o n data a r e p l o t t e d i n f i g u r e 2. The o r d i n a t e i s t h e tov/ing v e l o c i t y m u l t i p l i e d by the c o s i n e o f t h e angle o f a t t a c k .

The r a t e o f r o t a t i o n o f a c o s i n e - t y p e p r o p e l l e r i s designed t o be a f u n c t i o n o f o n l y t h a t component o f t h e v e l o c i t y v e c t o r w h i c h i s p a r a l l e l t o t h e a x i s o f t h e meter. An a n a l y s i s o f t h e i n d i v i d u a l p o i n t s i n f i g u r e 2 i n d i c a t e s t h a t t h e meter does n o t e x a c t l y measure o n l y t h e a x i a l component, b u t as t h e angle o f a t t a c k i n c r e a s e s , t h e meter p r o -p e l l e r -p r o g r e s s i v e l y r o t a t e s s l i g h t l y f a s t e r than i t should. However, f o r angles up t o 30°, a s i n g l e curve h a v i n g a maximum e r r o r o f about 3 p e r c e n t can be dra^^n t h r o u g h a l l p o i n t s . A t 45° t h e e r r o r i n c r e a s e s r a p -i d l y f o r v e l o c -i t -i e s g r e a t e r than 4 f e e t per second.

The o r i e n t a t i o n o f t h e VADA u n i t v j i t h r e s p e c t t o magnetic n o r t h i s g i v e n on a remote i n d i c a t o r d i a l . Attempts t o r e c o r d t h e d i a l r e a d -i n g by s -i m p l e means f a -i l e d ; t h e e l e c t r -i c a l s -i g n a l s betv;een t h e compass and i n d i c a t o r a r e n o t s u i t a b l e f o r r e c o r d i n g , and t h e t o r q u e a t t h e i n d i c a t o r needle i s t o o s m a l l t o d r i v e even s e n s i t i v e m i c r o p o t e n t i o m e t e r s . A s a t i s f a c t o r y system was achieved by f o l l o w i n g the needle o f an aux-i l aux-i a r y aux-i n d aux-i c a t o r w aux-i t h a servo mechanaux-ism h a v aux-i n g two photo daux-iode sensors. The servo motor i s coupled t o a p o t e n t i o m e t e r t o produce an analog s i g -n a l which i s r e c o r d e d .

The h e i g h t o f t h e VADA u n i t above t h e streambed i s c o n t i n u a l l y t r a c e d on t h e s t r i p - c h a r t o f t h e r e c o r d i n g f a t h o m e t e r . The a b s o l u t e v e l o c i t y and d r i f t angle o f t h e boat are measured w i t h a JN-400A Under-water Doppler N a v i g a t o r — a s o n i c i n s t r u m e n t system manufactured by Janus P r o d u c t s , I n c . — a n d are recorded on s t r i p - c h a r t r e c o r d e r s . The magnetic heading o f t h e boat i s r e c o r d e d by photographing t h e f a c e o f the boat compass every 1-1/2 seconds w i t h a motion p i c t u r e camera. A l t h o u g h t h e boat heading can be r e c o r d e d by t h e same method as i s used to r e c o r d t h e o r i e n t a t i o n o f t h e VADA u n i t , t h e l e s s expensive camera

VADA CABLE AND SLIP RINGS COMPASS DJDICATOR AUXILIART SERVO COMPASS COMPASS INDICATOR FOLLOWER

AMPLIFIER _{METER WITH} FREQUENCY ANALOG OUTPUT! RECORDING FATHOMETER STRIP CHART RECORDER STRIP CHART RECORDER BOAT COMPASS CAMERA JANUS NAVIGATOR STRIP CHART RECORDER F i g u r e

RADIONUCLIDE MOVEMENT

J = 1 = L - = I

^

J = I

688 _{C O A S T A L ENGINEERING}

method i s used because the heading does n o t v a r y r a p i d l y . A l l r e c o r d e d d a t a a r e p u t on a common time base by means o f event markers t r i g g e r e d by a common m a n u a l l y - o p e r a t e d s w i t c h .

Discharge i s measured by o b s e r v i n g t h e e n t i r e v e l o c i t y p r o f i l e at a s e r i e s o f v e r t i c a l s along a cross s e c t i o n . For each v e r t i c a l , t h e boat I S p o s i t i o n e d a p p r o x i m a t e l y on t h e cross s e c t i o n l i n e and k e p t as s t a t i o n a r y as p o s s i b l e by heading i n t o t h e c u r r e n t and u s i n g power D u r i n g times o f l o w f l o w , a sea anchor, which i s a canvas cone s i m i l a r t o a wind sock, i s towed t o improve boat h a n d l i n g . Iflien t h e boat i s p o s i t i o n e d , t h e VADA u n i t i s lowered t o t h e streambed, r a i s e d s l i g h t l y a l l o w e d t o s t a b i l i z e , and then r a i s e d s l o w l y t o t h e s u r f a c e . The v e r t i -c a l v e l o -c i t y o f t h e meter i s r e g u l a t e d so t h a t t h e angle o f a t t a -c k i s l e s s t h a n 20°, As t h e u n i t i s r a i s e d t h e f o l l o w i n g a r e r e c o r d e d con-t i n u o u s l y (see f i g . 3 ) : con-t h e r e l a con-t i v e wacon-ter v e l o c i con-t y , V,^ ^; con-t h e a b s o l u con-t e v e l o c i t y o f t h e b o a t , V^; t h e o r i e n t a t i o n o f t h e VADA u n i t , o( ^ ; t h e b o a t heading,ej'^^j^; t h e d r i f t angle of t h e b o a t. o C ^ ^ ^ ; and t h e ' h e i g h t o f the meter above i-hp st-i-o

For t h e d i s c h a r g e computation, t h e two v e l o c i t i e s , V^^ ^ and Vb, a r e added v e c t o r i a l l y t o g i v e V„, t h e a b s o l u t e v e l o c i t y o f t h e water (see f i g . 3 ) ; t h e v e c t o r a d d i t i o n i s c a r r i e d o u t a t a number o f p o i n t s i n each v e r t i c a l . V, t h e component o f V normal t o t h e cross s e c t i o n , i s computed f o r each o f t h e p o i n t s i n t h e v e r t i c a l and, i n t u r n , i s used t o c a l c u l a t e a d i s c h a r g e p e r u n i t w i d t h f o r t h e increment of d e p t h r e p r e s e n t e d by the p o i n t . These discharges a r e summed over the v e r t i c a l t o g i v e a d i s c h a r g e per u n i t w i d t h f o r t h e e n t i r e v e r t i c a l . The d i s c h a r g e f o r t h e s e c t i o n r e p r e s e n t e d by t h e v e r t i c a l i s determined by m u l t i p l y i n g t h e s e c t i o n vri.dth, which i s computed a c c o r d i n g t o t h e s t a n d a r d m i d s e c t i o n method, by t h e d i s c h a r g e per u n i t i r i d t h f o r t h e v e r t i c a l . men t h e s t r e a m f l o w i s c o n s t a n t , t h e t o t a l d i s c h a r g e can be computed as t h e sum o f t h e s e c t i o n d i s c h a r g e s . However, when t h e stream-f l o w changes r a p i d l y w i t h t i m e , s e c t i o n d i s c h a r g e s stream-f r o m a s e r i e s o stream-f com-p l e t e d i s c h a r g e measurements s h o u l d be used i n t h e f o l l o w i n g way t o d e f i n e a hydrograph. For each measurement, t h e cross s e c t i o n i s d i v i d e d i n t o s e v e r a l p a r t s . The d i s c h a r g e i n each p a r t i s determined by adding t h e d i s c h a r g e s f r o m t h e s e c t i o n s i n c l u d e d i n t h e p a r t . Then, d i s c h a r g e s f o r each p a r t are p l o t t e d as f u n c t i o n s o f t i m e t o g i v e a hydrograph f o r each p a r t . F i n a l l y , a hydrograph o f the t o t a l d i s c h a r g e i s computed by summing t o g e t h e r t h e hydrographs f o r each p a r t .

_ The accuracy o f t h e boat discharge measurement t e c h n i q u e was i n v e s t i g a t e d by comparing d i s c h a r g e s o b t a i n e d by the boat t e c h n i q u e w i t h t h o s e o b t a i n e d by s t a n d a r d U.S. G e o l o g i c a l Survey methods. Measurements were made i n t h e main channel o f the Columbia R i v e r a t Vancouver, Wash where t h e Td.dth i s a p p r o x i m a t e l y 2,800 f e e t . Due t o t i d e s , t h e d i s -charge m t h e channel i s unsteady; however, t h e f l u i d d e n s i t y i s homo-geneous and v e l o c i t y p r o f i l e s a r e t y p i c a l o f deep i n l a n d streams. Con-v e n t i o n a l measurements were made f r o m the U.S. Highway 99 b r i d g e u s i n g s t a n d a r d power-operated equipment and the 0.2 and 0.8 depth method ( C o r b e t t , 1962). S i m u l t a n e o u s l y , e x p e r i m e n t a l measurements by t h e new

690 COASTAL ENGINEERING

boat t e c h n i q u e were made about 2,000 f e e t upstream f r o m t h e b r i d g e . The d a t a o b t a i n e d from t h e measurements are p r e s e n t e d in- f i g u r e 4. The d i s c h a r g e hydrograph i s based on measurements from t h e b r i d g e and was c a l c u l a t e d by p a r t i t i o n i n g t h e cross s e c t i o n i n t o f i v e p a r t s and summing t h e discharges from each p a r t a t a number o f d i f f e r e n t times as p r e v i o u s l y d e s c r i b e d . Because o f equipment m a l f u n c t i o n s , o n l y t h r e e e x p e r i m e n t a l boat measurements vrere made. T h e r e f o r e , t h e p a r t i t i o n i n g and summing t e c h n i q u e c o u l d n o t be a p p l i e d t o d e f i n e a comparable h y d r o -graph. The t o t a l d i s c h a r g e f o r each of t h e t h r e e measurements i s p l o t t e d at t h e d i s c h a r g e w e i g h t e d mean t i m e o f each measurement. I f t h e h y d r o graph o b t a i n e d from t h e b r i d g e measurements i s used as an a b s o l u t e r e f e r -ence, t h e e r r o r s i n t h e boat measurements a r e 0, +2, and -5 p e r c e n t , r e s p e c t i v e l y . The g e n e r a l l y c l o s e agreement between t h e d i s c h a r g e s f r o m t h e boat measurements and t h e hydrograph i n d i c a t e s t h a t t h e new t e c h -n i q u e i s s u f f i c i e -n t l y a c c u r a t e f o r most s t u d i e s .

D u r i n g t h e boat measurements, t h e t i m e r e q u i r e d t o make observa-t i o n s a observa-t a v e r observa-t i c a l and observa-t o move observa-t o observa-t h e n e x observa-t v e r observa-t i c a l averaged ^ m i n u observa-t e s . More t h a n h a l f o f t h i s t i m e was spent p o s i t i o n i n g t h e boat and s t a b i l i z

-i n g -i t a t a s u -i t a b l e low v e l o c -i t y and d r -i f t a n g l e . The a c t u a l observa-t i o n s a observa-t each v e r observa-t i c a l r e q u i r e d abouobserva-t one minuobserva-te and v e r y l i observa-t observa-t l e observa-t i m e was spent i n moving from v e r t i c a l t o v e r t i c a l . On t h e b a s i s o f t h i s e x p e r i e n c e , i t appears t h a t d i s c h a r g e measurements can be made i n t h e e s t u a r y i n about 1.5 h o u r s , even a t cross s e c t i o n s 4 m i l e s w i d e .

MEASUREMENT OF RADIOACTIVITY

I n s i t u r a d i a t i o n measurements o f t h e bed sediment a r e made t o d e f i n e t h e a r e a l d i s t r i b u t i o n o f r a d i o a c t i v i t y i n t h e e s t u a r y . ^^^^ r a d i a t i o n i s m o n i t o r e d w i t h a s i n g l e - c h a n n e l a n a l y z e r system t o s u p p l y i n f o r m a t i o n on t h e r e l a t i v e amounts o f r a d i o a c t i v i t y . P r e c i s e measure-ments o f t h e a b s o l u t e amounts and k i n d s o f r a d i o n u c l i d e s a r e made byc o u n t i n g samples i n a l a b o r a t o r y u s i n g l a r g e and s o p h i s t i byc a t e d m u l t i -channel systems.

A s c i n t i l l a t i o n d e t e c t o r encased i n a v/aterproof a l u m i n u m hous-i n g t h a t has a 3/8-hous-inch t h hous-i c k bottom hous-i s used f o r f hous-i e l d c o u n t hous-i n g ( s e e p hous-i . I B ) . The d e t e c t o r i s a 5-inch by 2 - i n c h p l a s t i c phosphor o p t i c a l l y coupled t o a 3 - i n c h p h o t o m u l t i p l i e r tube. Housed v j i t h t h e d e t e c t o r a r e a p r e a m p l i f i e r and a h i g h - v o l t a g e supply. The d e t e c t o r and p r e a m p l i f i e r are padded w i t h sponge rubber f o r p r o t e c t i o n a g a i n s t m e c h a n i c a l shocks. The h i g h - v o l t a g e s u p p l y i s a 1,260-volt annular b a t t e r y pack c o n s i s t i n g of f o r t y - t v ; o 3 0 - v o l t b a t t e r i e s w i r e d i n s e r i e s . An o n - o f f s w i t c h and a v o l t a g e t e s t - j a c k are mounted on t h e b a t t e r y pack; b o t h t h e s w i t c h and j a c k are a c c e s s i b l e when plugs are removed from t h e w a t e r p r o o f h o u s i n g .

RADIONUCLIDE MOVEMENT 691

PACIFIC STANDARD TIME

F i g u r e 4. Discharges f o r m a i n channel of Columbia R i v e r at Vancouver, Wash., September 22, 1965

6 9 2 COASTAL ENGINEERING

P L A T E 1

A. Velocity-azimuth-depth assembly (VADA)

B. Radiation detector housing and components: (a) b a t t e r y pack, (b) phosphor, (c) p h o t o m u l t i p l i e r tube, (d) p r e a m p l i f i e r ,

(e) annular shield, (f) housing, (g) conical shield

RADIONUCLIDE MOVEMENT 693

Tv7o l e a d s h i e l d s a t t e n u a t e r a d i a t i o n emanating from around and

from above t h e d e t e c t o r . An annular s h i e l d t h a t f i t s around t h e lower p a r t o f t h e housing s h i e l d s t h e phosphor from t h e s i d e s ; a c o n i c a l s h i e l d t h a t forms a hood i n s i d e the housing s h i e l d s t h e phosphor from above.

The p a r t s o f the r a d i a t i o n c o u n t i n g equipment on board t h e boat c o n s i s t o f an a m p l i f i e r , a s i n g l e - c h a n n e l p u l s e - h e i g h t a n a l y z e r , a s c a l e r , and a r a t e meter h a v i n g an o u t p u t t o a s t r i p - c h a r t r e c o r d e r .

The d e t e c t o r housing mounts i n a s l e d ( p i . IC) f o r t o w i n g over t h e bottom. The tovj l i n e i s a 3/16-inch OD, s i n g l e - c o n d u c t o r , armored cable t h a t a l s o serves as the s i g n a l l i n e . The cable vri.nds on a power winch, which i s used t o r a i s e and lower t h e s l e d . D u r i n g tovrilng, t h e

I'jinch i s f r e e t o r o t a t e , and t h e cable i s clamped t o a s a f e t y r e l e a s e mechanism mounted on the s t e r n o f t h e b o a t . I'Jhenever t h e s l e d catches on a submerged o b j e c t and t h e t e n s i o n i n the cable exceeds a . p r e d e t e r -mined amount, t h e s a f e t y mechanism r e l e a s e s the c a b l e . The c a b l e t h e n unwinds f r e e l y u n t i l f o r w a r d m o t i o n o f t h e boat i s stopped. As an a d d i t i o n a l p r e c a u t i o n , a s a f e t y l i n e w i t h a buoy i s a t t a c h e d t o t h e back of t h e s l e d so t h a t i t can be d i s l o d g e d from the r e a r i f necessary.

D u r i n g t h e f i r s t weeks o f t o w i n g , t h e s l e d snagged a number o f t i m e s . A l t h o u g h the s a f e t y f e a t u r e s o f t h e system operated s a t i s -f a c t o r i l y , much t i m e V7as V7asted i n f r e e i n g the s l e d ; t h e r e f o r e , t o w i n g was d i s c o n t i n u e d except i n p l a c e s c l e a r e d o f snags by commercial g i l l n e t f i s h e r m e n . O r d i n a r i l y , t h e system nov; i s used as a q u a s i - p o i n t measuring d e v i c e . I'Jhen used i n t h i s way, the s l e d i s lowered t o t h e bottom w h i l e t h e boat i s s l o w l y moving ahead. The boat then hovers i n one spot or s l o w l y tov7s t h e s l e d over the bottom. A f t e r a s t a t i s t i c a l l y s i g n i f i c a n t count i s o b t a i n e d , t h e s l e d i s r a i s e d and t h e boat i s moved to a new l o c a t i o n . The c a b l e r e l e a s e mechanism i s n o t a t t a c h e d when t h e s l e d i s used i n t h i s way.

D u r i n g e a r l y e x p e r i m e n t a t i o n , a mercury t i l t s w i t c h v?as mounted on t h e s l e d t o t u r n a l i g h t on i n t h e s a f e t y buoy whenever t h e s l e d was r i g h t s i d e up. However, i t was found t o be almost i m p o s s i b l e t o s e t t h e s l e d dovm i n any way b u t r i g h t s i d e up, e s p e c i a l l y i n flovzing water or V7hile t h e b o a t was s l o w l y under V7ay. Hence, the s w i t c h V7as removed and t h e l i g h t e d buoy was r e p l a c e d by a s m a l l torpedo-shaped buoy. I f t h e s l e d i s s e t on t h e bottom upside down o r on one s i d e , i t i s r e a d i l y apparent because the count r a t e i s an order o f magnitude lower t h a n t h e r a t e n o r m a l l y measured on t h e bed.

COLLECTION OF WATER-SEDIMENT SAMPLES

Samples o f water and suspended sediment supply d a t a on t h e amounts and k i n d s o f r a d i o n u c l i d e s i n s o l u t i o n and suspension, and on t h e d i s t r i -b u t i o n and c h a r a c t e r o f the sediments. I n order t o p r o v i d e s u f f i c i e n t m a t e r i a l f o r t h e v a r i o u s analyses, 6 - g a l l o n samples must be c o l l e c t e d . A l s o , samples must be c o l l e c t e d r a p i d l y , must be f r e e o f r e s i d u a l r a d i o -a c t i v e c o n t -a m i n -a t i o n f r o m t h e s-ampler, -and must be r e p r e s e n t -a t i v e o f t h e water-sediment m i x t u r e .

V a l v e 0 3 - W a y V a l v e A i r Lino Disposable L i n e W a t e r L i n e to Pressure Gage A i r B l e e d e r F l o a t - S w i t c h C a b l e Vacuum- Pressure Pump O

i

i

S a m p l e r W e i g h t D r a i n

RADIONUCLIDE MOVEMENT 695

The sampler (see f i g , 5 ) designed t o meet these requirements c o l l e c t s d u p l i c a t e 3 - g a l l o n samples a t stream v e l o c i t y from s i n g l e p o i n t s and operates a t f l o v 7 r a t e s up t o 2,5 g a l l o n s per minute. To e l i m i n a t e r e s i d u a l c o n t a m i n a t i o n , a l l p a r t s t h a t come i n c o n t a c t v;ith the samples are d i s c a r d e d p e r i o d i c a l l y . I n order t o minimize t h e num-ber o f d i s p o s a b l e p a r t s , a s u c t i o n system i s used r a t h e r than a pumpi n g system. A l l plumbpumping t h r o u g h whpumpich the samples pass pumpi s e pumpi t h e r p o l y -e t h y l -e n -e o r p o l y v i n y l c h l o r i d -e (PVC). Both m a t -e r i a l s ar-e r -e l a t i v -e l y i n e x p e n s i v e and b o t h sorb r a d i o n u c l i d e s l e s s r e a d i l y t h a n o t h e r common hose and t u b i n g m a t e r i a l s . R e p r e s e n t a t i v e samples are o b t a i n e d by c o l l e c t i n g w a t e r and sediment a t f r e e stream v e l o c i t y .

Flow e n t e r s t h e sampler through an i n t a k e n o z z l e i n t h e nose o f a 300-pound s t r e a m l i n e d w e i g h t and then passes up a s e m i f l e x i b l e 1/2-inch p o l y e t h y l e n e p i p e t o t h e c o l l e c t i o n system on board t h e boat. I n i t i a l l y , t h e f l o w i s d i r e c t e d t h r o u g h a f l o w r a t e meter i n t o a 9 g a l -l o n s t o r a g e t a n k . The f -l o w r a t e i s a d j u s t e d by v a r y i n g t h e vacuum i n the system by means o f an a i r bleeder v a l v e u n t i l the flov? e n t e r s t h e i n t a k e n o z z l e a t t h e f r e e - s t r e a m v e l o c i t y , which i s measured p r i o r t o sampling. When t h e p r o p e r f l o w r a t e i s s t a b i l i z e d , t h e s t o r a g e t a n k i s bypassed and t h e sample i s d i r e c t e d i n t o one o f t h e two 3 - g a l l o n b o t t l e s . A f t e r one b o t t l e i s f i l l e d , the f l o w can be d i r e c t e d i n t o the second b o t t l e , back t o t h e storage t a n k , o r stopped. F i e l d t e s t s

shov7 t h a t the f l o w r a t e e n t e r i n g t h e b o t t l e s i s w i t h i n 5 p e r c e n t o f

t h a t i n d i c a t e d by t h e f l o w - r a t e meter.

A f t e r sampling i s completed, t h e s t o r a g e t a n k i s emptied by opening a v a l v e a t t h e bottom. P r e s s u r i z i n g t h e t a n k speeds t h e d r a i n -age. The a i r pressure-vacuum pump i s p r o t e c t e d a g a i n s t o v e r f l o w f r o m the s t o r a g e t a n k by a f l o a t s w i t c h i n the t a n k .

SEPARATION OF WATER-SEDIMENT SAMPLES FOR LABORATORY ANALYSES Water-sediment samples are processed f o r l a b o r a t o r y analyses by s e p a r a t i n g t h e sediment f r o m t h e water on board t h e boat w i t h a

s p e c i a l l y designed h i g h - f l o w f i l t e r system. Samples c o l l e c t e d f o r r a d i o n u c l i d e analyses are separated t o p r o h i b i t i n t e r c h a n g e between the r a d i o n u c l i d e s i n s o l u t i o n and those sorbed on t h e sediments. Samples c o l l e c t e d f o r sediment c o n c e n t r a t i o n and s i z e analyses, a r e separated t o e l i m i n a t e t h e h a n d l i n g o f l a r g e volumes o f water.

The f i l t e r system, which i s shovm i n p l a t e 2A and f i g u r e 6, has a b o t t l e c o n t a i n e r t h a t accepts a 3 - g a l l o n sample b o t t l e . A s t a i n l e s s s t e e l t u b e , a t t a c h e d t o t h e b o t t l e c o n t a i n e r cover on one end and hav-i n g a s p r hav-i n k l e r head on t h e o t h e r end, hav-i n s e r t s hav-i n t o t h e b o t t l e when t h e cover i s p u t i n p l a c e . The cover makes separate p r e s s u r e - t i g h t s e a l s on b o t h t h e c o n t a i n e r and t h e b o t t l e . I n o p e r a t i o n , t h e c o n t a i n e r i s i n v e r t e d and connected t o t h e p r e s s u r e - f i l t e r h o l d e r w i t h a q u i c k - a c t i n g c o u p l i n g . The c o n t a i n e r and t h e i n s i d e o f the sample b o t t l e a r e p r e s -s u r i z e d a t 30 t o 45 pound-s per -square i n c h w i t h a i r from a 7 2 - c u b i c f o o t SCUBA tank. A i r i s s u p p l i e d t o t h e b o t t l e t h r o u g h t h e s t a i n l e s s s t e e l tube and t o t h e c o n t a i n e r t h r o u g h a d i r e c t t a p . The pressures on t h e

O» CO 05 . S p r i n k i s r C o n t a i n e r F i l t e r <8> © A i r B l e e d e r ^ Pressure Regulator ii y - 1^ Rinse W a t e r R e s e r v o i r V a l v e 3 - W a y V a l v e C o u p l i n g A i r L i n e A i r - W a t e r L i n e W o t e r L i n e F i l t e r P a t h R i n s e P a t h SCUBA T a n k O

i

r w

I

6 9 8 C O A S T A L ENGINEERING

i n s i d e and t h e o u t s i d e o f t h e b o t t l e are e q u a l i z e d t o m i n i m i z e leakage and s t r e s s i n t h e b o t t l e . The p r e s s u r e f o r c e s t h e water t h r o u g h a 12i n c h d12iameter c e l l u l o s e e s t e r membrane f 12i l t e r wh12ich removes a l l p a r t 12i -c l e s -c o a r s e r t h a n about 0.3 m i -c r o n s . A f t e r t h e sample i s f i l t e r e d , the b o t t l e i s r i n s e d w i t h water i n j e c t e d t h r o u g h t h e s t a i n l e s s s t e e l tube and s p r i n k l e r head. T h i s water a l s o i s f i l t e r e d . A f t e r t h e b o t t l e i s emptied and r i n s e d , t h e c o n t a i n e r i s d i s c o n n e c t e d f r o m t h e f i l t e r and r o t a t e d t o an u p r i g h t p o s i t i o n . Iflien d i s c o n n e c t e d , t h e f i l t e r h o l d e r , which i s mounted on a c a n t i l e v e r e d l i n k a g e , can be swung o u t and t h e f i l -t e r elemen-t r e p l a c e d .

Both t h e f i l t e r e d sediments and f i l t r a t e s o f t h e r a d i o n u c l i d e samples are saved and sent t o t h e B a t t e l l e - N o r t h w e s t L a b o r a t o r i e s a t R i c h l a n d , Wash, f o r d e t a i l e d analyses. I n t h e l a b o r a t o r y , t h e membrane f i l t e r s c o n t a i n i n g t h e sediments are d r i e d , c u t i n t o s m a l l p i e c e s , and suspended i n agar agar f o r c o u n t i n g . The f i l t r a t e s are evaporated t o r e s i d u e s b e f o r e c o u n t i n g .

Only t h e f i l t e r e d sediments o f t h e samples c o l l e c t e d f o r sediment c o n c e n t r a t i o n and s i z e analyses are r e t a i n e d ; t h e f i l t r a t e s a r e d i s c a r d e d a f t e r t h e i r volumes are d e t e r m i n e d . Before l a b o r a t o r y analyses o f t h e sediments can be performed, t h e sediments must f i r s t be removed f r o m t h e f i l t e r s . Various techniques f o r removing sediment from t h e f i l t e r s have been c o n s i d e r e d . I n g e n e r a l , simple mechanical techniques such as s c r a p i n g and back f l u s h i n g a r e u n s a t i s f a c t o r y . C u r r e n t l y , a t e c h n i q u e u t i l i z -i n g chem-ical t r e a t m e n t -i s b e -i n g e v a l u a t e d . T h -i s t e c h n -i q u e -i n v o l v e s f -i r s t d i s s o l v i n g t h e f i l t e r i n acetone. Next, t h e a c e t o n e - f i l t e r - s e d i m e n t m i x t u r e i s washed id.th acetone i n t o a c e n t r i f u g e tube c o n t a i n i n g g l y c e r -i n e . Because acetone and g l y c e r -i n e do n o t m-ix, c e n t r -i f u g -i n g s e p a r a t e s the sediment f r o m t h e a c e t o n e - f i l t e r s o l u t i o n , and t h e sediment accumu-l a t e s i n t h e g accumu-l y c e r i n e a t t h e bottom o f t h e c e n t r i f u g e t u b e . A f t e r d e c a n t i n g t h e a c e t o n e - f i l t e r s o l u t i o n , the g l y c e r i n e - s e d i m e n t m i x t u r e i s r e p e a t e d l y d i l u t e d w i t h d i s t i l l e d w a t e r , c e n t r i f u g e d and decanted u n t i l o n l y an e s s e n t i a l l y pure water-sediment m i x t u r e remains.

Organic compounds such as acetone and g l y c e r i n e may cause changes i n t h e s i z e d i s t r i b u t i o n o f some sediments (Grim, 1953, p. 251-277). To check t h e e x t e n t o f these changes, s i z e analyses were performed on t r e a t e d (acetone and g l y c e r i n e ) and on u n t r e a t e d s p l i t s from two Columbia R i v e r e s t u a r y sediment samples. The f i r s t sample was s p l i t i n t o two p a r t s , A and B. These were again s p l i t t o g i v e f o u r subparts each. The f o u r subp a r t s o f A were sussubpended i n water and f i l t e r e d u s i n g t h e h i g h f l o w f i l t e r system. The f i l t e r and sediment were separated by t h e c h e m i c a l t e c h -n i q u e . The f o u r subparts o f A a-nd B were the-n a-nalyzed f o r p a r t i c l e s i z e by s t a n d a r d v i s u a l a c c u m u l a t i o n t u b e p i p e t t e t e c h n i q u e s . Size d i s -t r i b u -t i o n f o r p a r -t s A and B ( f i g . 7) were compu-ted by a v e r a g i n g -t h e s i z e d i s t r i b u t i o n s o f t h e i r r e s p e c t i v e s u b p a r t s . The maximum d i f f e r e n c e be-tween any i n d i v i d u a l p e r c e n t f i n e r v a l u e o f a subpart and t h e v a l u e f o r the same s i z e from t h e average d i s t r i b u t i o n was l e s s t h a n 2 p e r c e n t . The second sample was s p l i t i n t o two p a r t s , l a b e l e d C and D. P a r t C and a f i l t e r were mixed w i t h acetone, and t h e sediment was r e c o v e r e d by u s i n g the s e p a r a t i o n t e c h n i q u e . P a r t s C and D were then analyzed by t h e

RADIONUCLIDE MOVEMENT 699

Figure 7. Particle size distributions of treated and untreated sediment samples

7 0 0 C O A S T A L ENGINEERING

s t a n d a r d t e c h n i q u e . The r e s u l t s o f these analyses a l s o are g i v e n i n f i g u r e 7,

These t e s t s i n d i c a t e t h a t t h e combined e f f e c t s o f acetone, g l y c e r i n e , and c e n t r i f u g i n g cause l i t t l e measurable change i n p a r t i c l e s i z e d i s t r i b u t i o n s . The d i f f e r e n c e s between the s i z e d i s t r i b u t i o n s o f the t r e a t e d and t h e u n t r e a t e d samples p r o b a b l y are due t o i n t r i n s i c i n a c c u r a c i e s o f t h e analyses,

CORE SAMPLING

The bed o f t h e e s t u a r y i s m a i n l y sand, a l t h o u g h f i n e - g r a i n e d d e p o s i t s are n o t uncommon. I n o r d e r t o i n v e s t i g a t e the d i s t r i b u t i o n o f r a d i o a c t i v i t y and the s e d i m e n t a t i o n c h a r a c t e r i s t i c s i n t h e bed, a p o r t -able core sampler was needed t h a t c o u l d p e n e t r a t e the sediment e a s i l y and t h a t c o u l d operate i n deep, r a p i d l y f l o w i n g water. To meet t h i s need, a sampler t h a t c o l l e c t s cores 6 f e e t l o n g and 1-7/8-inches i n diameter was developed. The sampler, which i s suspended by a s i n g l e cable and i s used from an anchored b o a t , has s u c c e s s f u l l y sampled d e p o s i t s submerged beneath 70 f e e t o f water f l o w i n g a t 5 f e e t per second.

The core sampler ( p i . 2B) u t i l i z e s v i b r a t i o n i n c o n j u n c t i o n w i t h an a x i a l f o r c e and s u c t i o n t o achieve p e n e t r a t i o n . The sampler c o n s i s t s o f ( 1 ) a core b a r r e l on top o f which i s mounted an e l e c t r o - m e c h a n i c a l v i b r a t o r i n a w a t e r p r o o f housing; ( 2 ) a s t r e a m l i n e d body; and ( 3 ) an i n t e r c o n n e c t i n g cable and clamp system arranged so t h a t t e n s i o n on t h e suspension c a b l e produces a do^mward f o r c e on t h e core b a r r e l , and a l s o p r o v i d e s support a g a i n s t h o r i z o n t a l f o r c e s .

The core b a r r e l i s a 2-1/8-inch OD s t a i n l e s s s t e e l tube i n t o which f i t s a 1-7/8-inch ID p l a s t i c l i n e r t h a t i s 6 f e e t l o n g . A t i g h t l y f i t t i n g p i s t o n s l i d e s i n s i d e the p l a s t i c l i n e r . The p i s t o n i s suspended from a p u l l e y on a l i g h t c a b l e ; one end o f t h e cable a t t a c h e s t o t h e v i -b r a t o r housing and t h e o t h e r end a t t a c h e s t o a clamp on t h e suspension c a b l e . D u r i n g c o r i n g , t h e p i s t o n s e t s on and remains s t a t i o n a r y w i t h r e s p e c t t o t h e bed. The r o t a r y v i b r a t o r d e l i v e r s 300 pounds of t h r u s t a t 60 c y c l e s per second.

The s t r e a m l i n e d body, which weighs 250 pounds, guides t h e c o r i n g tube and p r o v i d e s the r e a c t i v e f o r c e r e q u i r e d t o c o n v e r t t h e upward f o r c e on t h e suspension cable t o a dovmward f o r c e on the core b a r r e l . O u t r i g g e r s on t h e body supply a d d i t i o n a l l a t e r a l s t a b i l i t y t o the system. The core b a r r e l passes t h r o u g h a v e r t i c a l c a v i t y a t t h e c e n t e r o f t h e body and i s guided by two s e t s o f rubber r o l l e r s . A s p r i n g - l o a d e d cover p l a t e t h a t r o t a t e s i n a h o r i z o n t a l p l a n e i s f i t t e d t o the u n d e r s i d e o f the body t o cover t h e bottom o f t h e core tube a f t e r t h e tube i s withdravm f r o m t h e bed. Tv;o h o r i z o n t a l s p r i n g - l o a d e d l o c k i n g p i n s t h a t can be i n s e r t e d i n t o s o c k e t s on t h e core b a r r e l are mounted on top o f the s t r e a m l i n e d body and two v e r t i c a l s p r i n g - l o a d e d p i s t o n s are s i t u a t e d i n t h e body. The p i s t o n s a r e s l o t t e d so t h a t they r e t a i n tte h o r i z o n t a l p i n s i n t h e core b a r r e l s o c k e t s

RADIONUCLIDE MOVEMENT 701

p r i o r t o c o r i n g but a l l o w them t o r e t r a c t when the weight o f t h e sampler i s supported on t h e bed.

The sampler i s suspended by a 3/15-inch d i a m e t e r , 3-conductor, armored c a b l e . S i n g l e phase 2 3 0 - v o l t power i s s u p p l i e d t o t h e v i b r a t o r t h r o u g h t h e c a b l e . The c a b l e winds on a power winch h a v i n g an a u x i l i a r y hand crank and s l i p r i n g s . The suspension cable f a s t e n s t o t h e top o f t h e v i b r a t o r - c o r e b a r r e l assembly. The s t r e a m l i n e d body, i n t u r n , couples t o t h i s assembly by an i n t e r c o n n e c t i n g c a b l e t h a t l a c e s t h r o u g h p u l l e y s on t h e v i b r a t o r housing and on t h e tops o f the v e r t i c a l p i s t o n s i n t h e body (see p i . 2B). The ends o f t h e i n t e r c o n n e c t i n g c a b l e f a s t e n t o a s c i s s o r s - t y p e clamp t h a t seats on a c y l i n d r i c a l g r i p on t h e main suspension c a b l e . T h i s c a b l e g r i p i s f a s t e n e d t o t h e suspension c a b l e at a p o s i t i o n such t h a t when t h e clamp i s i n p l a c e and t h e i n t e r c o n n e c t -i n g c a b l e -i s t a u t , a l e n g t h o f s l a c k suspens-ion c a b l e s l -i g h t l y l o n g e r than t w i c e t h e l e n g t h o f t h e core b a r r e l e x i s t s betvreen t h e g r i p and t h e c a b l e c o n n e c t i o n at t h e top o f t h e v i b r a t o r housing.

I n p r e p a r i n g t h e sampler f o r c o r i n g , t h e h o r i z o n t a l l o c k i n g p i n s are s e t , the s c i s s o r s clamp i s seated on the c y l i n d r i c a l g r i p , and t h e s u c t i o n p i s t o n c a b l e i s connected t o t h e s c i s s o r s clamp. I n t h e p r e p a r e d p o s i t i o n , t h e l o c k i n g p i n s p r o h i b i t r e l a t i v e motion between t h e core b a r r e l and t h e body. The sampler i s lowered ( f i g . 8a) and t h e o p e r a t o r t u r n s on t h e v i b r a t o r when t h e body i s a few f e e t above t h e bed. When t h e sampler i s s e t on t h e bottom and t h e i n t e r c o n n e c t i n g cable r e l a x e s s l i g h t l y , t h e v e r t i c a l p i s t o n s draw do\m and a l l o w t h e l o c k i n g p i n s t o r e t r a c t f r o m t h e sockets i n t h e core b a r r e l . At t h i s p o i n t , t h e core b a r r e l i s f r e e t o p e n e t r a t e i n t o the bed. Immediately a f t e r t h e sam-p l e r i s s e t on t h e bed, t e n s i o n i s a sam-p sam-p l i e d t o t h e sussam-pension c a b l e by means o f t h e a u x i l i a r y hand crank. The up\rard f o r c e r e s u l t s i n a down-ward f o r c e on t h e core b a r r e l . The r e l a t i v e p o s i t i o n s o f the p a r t s o f t h e sampler d u r i n g c o r i n g are d e p i c t e d i n f i g u r e 8b. Cable i s r e e l e d i n and t h e core b a r r e l p e n e t r a t e s u n t i l a s w i t c h on t h e u n d e r s i d e o f t h e v i b r a t o r housing c o n t a c t s t h e top o f t h e s t r e a m l i n e d body. T h i s shuts o f f power t o t h e v i b r a t o r .

Next, a messenger sent doim t h e cable r e l e a s e s t h e s c i s s o r s clamp. IJhen t h e clamp r e l e a s e s , i t f a l l s past t h e upper c y l i n d r i c a l g r i p and catches on a l o o s e l y a t t a c h e d lower g r i p . The lower g r i p p r e -v e n t s t h e i n t e r c o n n e c t i n g cable from g o i n g t o t a l l y s l a c k and becoming t a n g l e d w i t h t h e r e s t o f t h e apparatus.

A f t e r t h e s c i s s o r s clamp r e l e a s e s ( f i g , 8 c ) , t h e core b a r r e l i s withdra\m from t h e bed by r e e l i n g i n t h e suspension c a b l e u s i n g power. At t h e same t i m e , t h e s c i s s o r s clamp and t h e lower g r i p s l i d e

do\m t o t h e end o f t h e suspension c a b l e , IJhen t h e lower g r i p reaches

t h e end o f t h e suspension c a b l e and t h e bottom of t h e core b a r r e l r e t r a c t s i n t o t h e body, t h e s p r i n g l o a d e d cover p l a t e c l o s e s , t h e i n t e r -c o n n e -c t i n g -cable a g a i n be-comes t a u t , and -c o n t i n u e d r e e l i n g l i f t s t h e body from t h e bed.

RADIONUCLIDE MOVEMENT 703

\flien t h e sampler i s r a i s e d t o t h e s u r f a c e , i t i s i n t h e p o s i t i o n shoim i n f i g u r e 8d. The sampler i s p l a c e d on deck i n a v e r t i c a l p o s i t i o n . A f t e r a p u l l e y on one o f t h e v e r t i c a l p i s t o n s i n t h e w e i g h t i s r e -moved, t h e core b a r r e l can be withdravm from t h e w e i g h t , and t h e d r i v i n g head removed. The p l a s t i c l i n e r c o n t a i n i n g the core can then be w i t h -draxm v e r t i c a l l y f r o m t h e core b a r r e l .

A t o t a l t i m e o f a p p r o x i m a t e l y 45 minutes i s r e q u i r e d t o o b t a i n each core. Most o f t h e t i m e i s spent anchoring t h e boat and p r e p a r i n g the sampler. A l t h o u g h p e n e t r a t i o n i s achieved i n about a m i n u t e , t h e sampler i s i n t h e water f o r a p p r o x i m a t e l y 5 minutes.

L o n g i t u d i n a l s e c t i o n s o f cores c o l l e c t e d vzith the sampler show l i t t l e d i s r u p t i o n o f t h e s t r a t i f i c a t i o n except f o r some i n t e r m i t t e n t w a r p i n g . The v i b r a t i o n p r o b a b l y a f f e c t s t h e s u r f a c e - t o - s u r f a c e c o n t a c t between g r a i n s ; h o v 7 e v e r , i t i s e v i d e n t t h a t i t does n o t cause any s i g -n i f i c a -n t displaceme-nt o f t h e p a r t i c l e s . Some p a r t i c l e displaceme-nt occurs when f i n e m a t e r i a l i s moved along t h e core l i n e r w a l l by t h e p e r -c o l a t i o n o f vjater w i t h i n t h e -core.

D u r i n g development o f t h e core sampler, s e v e r a l d i f f e r e n t d e v i c e s f o r r e t a i n i n g t h e core i n t h e b a r r e l were t e s t e d . A l l t h e c l o s i n g devices t h a t f i t i n t h e d r i v i n g head r e s t r i c t e d t h e entrance o f sediment i n t o t h e b a r r e l and i n h i b i t e d p e n e t r a t i o n . T e s t i n g , however, a l s o i n d i c a t e d t h a t cores c o u l d be o b t a i n e d i n many sediments w i t h o u t u s i n g any c l o s i n g de-v i c e , a p p a r e n t l y because o f compaction due t o de-v i b r a t i o n and because o f s u c t i o n due t o t h e p i s t o n . The s p r i n g - l o a d e d cover p l a t e was f o u n d t o be e f f e c t i v e i n r e d u c i n g the amount o f core l o s t when r e t e n t i o n proved d i f f i c u l t .

ACKNOÏJLEDGMENTS

The equipment and techniques were developed by p e r s o n n e l o f t h e Q u a l i t y o f Water Branch, Water Resources D i v i s i o n , U.S. G e o l o g i c a l Sur-vey, P o r t l a n d , Greg, as a p a r t o f a c o o p e r a t i v e study w i t h the U.S. Atomic Energy Commission. A b s o l u t e r a d i a t i o n c o u n t i n g o f samples i s done by B a t t e l l e - N o r t h w e s t L a b o r a t o r i e s . The a s s i s t a n c e r e c e i v e d f r o m Mr. George Smoot o f t h e Water Resources D i v i s i o n , U.S. G e o l o g i c a l Survey, Washington, D. C , i n d e v e l o p i n g the i n s t r u m e n t s f o r t h e w a t e r d i s -charge measuring system i s g r a t e f u l l y acknowledged.

REFERENCES

B a r r o n , E. G. (1963). New i n s t r u m e n t s f o r s u r f a c e v;ater i n v e s t i g a t i o n s , i n S e l e c t e d techniques i n water resources i n v e s t i g a t i o n s , c o m p i l e d bx Mesnier, N. G. and X s e r i , K. T.: U.S. Geol. Survey Water-Supply

Paper 1669-Z.

C o r b e t t , D. M. and o t h e r s (1962). Stream-gaging procedures; A manual d e s c r i b i n g methods and p r a c t i c e s o f t h e G e o l o g i c a l Survey; U.S. Geol. Survey Water-Supply Paper 888.

7 0 4 COASTAL ENGINEERING

Grim, Ralph E. (1953). Clay m i n e r a l o g y : McGraw-Hill Book Co., I n c . , New York-Toronto-London.

L o c k e t t , J. B. and Kidby, H. A. (1961). P r o t o t y p e measurements o f t h e . Columbia R i v e r E s t u a r y : Proc. Amer. Soc, o f C i v i l E n g i n e e r s , v o l . 87, No. HYl, pp. 57-83.