ML20150B716
| ML20150B716 | |
| Person / Time | |
|---|---|
| Site: | Hartsville  |
| Issue date: | 10/31/1978 |
| From: | Remick F, Venn Leeds J, Wolf J Atomic Safety and Licensing Board Panel |
| To: | |
| References | |
| NUDOCS 7811080219 | |
| Download: ML20150B716 (22) | |
Text
-
NRC PUBLIC DOCUMENT ROOM
("
'\\'
UNITED STATES OF AMERICA b
o NUCLEAR REGUIAIORY COMtGSSION if splBy r
.e I
goi Atomic Safety and Licensing Board 1
(
/p s
John F. Wolf, Chairman C3 Dr. J. Venn Leeds, Jr.
Dr. Forrest J. Remick IN THE MATTER OF
)
)
Docket Nos. SIN 50-518 TENNESSEE VALLEY AUIHORITY
)
STN 50-519
)
SIN 50-520 (Hartsville Nuclear Plant,
)
STN 50-521 Units lA, 2A, 1B and 2B)
)
DECISION ON M7FION FOR
SUMMARY
DISPOSITION (October 31, 1978)
The Tennessee Valley Authority (Applicant or TVA), pursuant to 10 CFR S 2.749 (1977), filed a notion for stumary disposition of the question of the acceptability of the construction of a discharge diffuser at a point in the Cumberland River between Dixon Island and the upstream end of a bed of an endangered species of mussel.~1/
i The notion was acconpanied by the affidavits of Robert O. Barnett, Jr.,
Billy G. Isom, Christopher D. Ungate, and Harold J. Monroe III; a statement of facts material to the location of the discharge diffuser 1/
Applicant's Fbtion for Summry Disposition On the Acceptability of Construction of the Discharge Diffuser at a Point Between Dixon Island and the Upstream End of the Mussel Bed, dated March 20, 1978.
78110804L(9
1 e
e o
2 as to which the Applicant claims there is not a genuine issue to be heard; and Applicant's brief in support of the motion.
Intervenors William N. Young, et a_l,. (Intervenors), in answer-l l
ing Applicant's notion for sumary -disposition, contended that the lack of evidence from the Department of Interior on the diffuser. Location issue precludes the Intervenors from presenting facts to justify their 2/
~
opposition to the Applicant's notion for summary disposition.
The answer was acconpanied by a statement of facts material to the location of the discharge diffuser as to which Intervenors claim that there is a ;enuine issue to be heard; and an Affidavit of Robert Jack Neff.
They conte d that there are issues of material fact concerning the impact on the endangered species from heated water that would be dis-charged from an upstream location of the diffuser, and concerning the inpacts on the endangered species from radionuclides that would be discharged, and from other enviwuaental factors, if the diffuser were located upstream.
I Intervenors' statement of material facts as to which there are genuine issues to be heard indicates that they agree with TVA's state-ment of facts numbered 1 and 2.
However, they indicate that TVA's statement of facts number 3 through 7 are statements as to which there are genuine issues to be heard.
-2/
Answer of Intervenors, William N. Young, et al. To Applicant's MotionForSummaryDispositionontheAcc5taEilityofConstruc-tion of the Discharge Diffuser at a Point Between Dixon Island and the Upstream End of the Mussel Bed, dated June 7, 1978.
3 In a filing dated June 7,1978, the NRC Staff stated that for the reasons set out in attached affidavits (both dated June 6, 1978) by Dr. Charles W. Billups and William S. Bivins, respectively, it " supports" the Applicant's notion for sumary disposition on the acceptability of the construction of the discharge diffuser at a point between Dixon Island and the upstream end of the nussel bed.-3/
The Board's findings regarding facts as to which Applicant i
contends there is no genuine issue to be heard, follow.
4 Proposed Statement of Fact Number 1 A nussel bed in the Cumberland River at mile 284.1 contains some specimens of the endangered nussel species Lamsilis orbiculata, also known as the pink nucket pearly nussel.
The Intervenors agree with TVA's statement of fact No. 1.
i
' The Board finds that there is no genuine issue of fact to be heard as to TVA's statement of fact No. 1.
Proposed Statement of Fact Number 2 The Nuclear Regulatory Comnission has consulted
]
with the Department of the Interior concerning the acceptability of construction of the Hartsville Nuclear Plants discharge diffuser in the area between Db:en Island and the upstream edge of the nussel bed.
The Intervenors agree with TVA's statement of fact No. 2.
-3/
NRC Staff Response to Applicant's Motion for Sumary Disposition, dated ' ne 7,11978.
l 4
I The Board finds that there is no genuine issue of fact to be heard as to TVA's statemerc of fact No. 2.
Proposed Statement of Fact Ntmer 3 The Biological Ooinion of the Department of the Interior is that coratruction of the discharge diffuser in the area betweca Dimon Island and the upstream edge of the mussel bed will not jeopardize the continued existence of the pink nucket pearly nussel, L.
orbiculata.
The Intervenors indicate that the Biological Opinion letter of the Department of Interior does not support the position taken by the Applicant. The Intervenors correctly point otrc that the Biological Opinion does not state that construction of the discharge diffuser in the area between Dixon. Island and the upstream edge of the mussel bed (upstream location) will not jeopardize the continued existence of the pink mucket pearly nussel. The Biological Opinion indicates that the construction and operation of the diffuser "... are not likely to jeopardize the continued existence..." of the endangered species.-4/
1 The Opinion 1:etter indicates only that the cor.ruction and operation of the discharge diffuser, if placed in the area between Dixon Island and the upstream edge of the mussel bed, are not likely to jeopardize the continued existence of the endangered pirA nucket pearly mussel. The Board finds that in the context of deciding this 4f Exhibit 1 to Applicant's brief in ' support for sucmary disposition, at 1 and 3.
a n
i 5
1 notion the distinction between "... are not likely to jeopardize..."
and "... will not jeopardize..." is not significant.
It is clear from the Biological Opinion that the Department of Interior has approved I
the proposed location of the diffuser discharge from the standpoint of its possible impact on the endangered species.
The Appeal Board indicated in deciding an appeal by the same Intervenors of one of this Board's earlier findings that "The law attaches no magical significance to the incantation of a special phrase" and that " Insignificant effects 5/
are not proscribed by the statute.'"
The Board finds that the construction and operation of the diffuser discharge at the upstream location will not jeopardize the continued existence of the endangered pink mucket pearly mussel, Lamosilis_orbiculata. Therefore, there is not a genuine issue of mate-rial fact to be heard as to TVA's statement of fact No. 3.
Proposed Statement of Fact Number 4 The record in this proceeding confirms the opinion of the Department of the Interior that the small anount of sediment which would be added by construction of the discharge diffuser will not adversely affect the mussels.
The Intervenors contend that the proposed statement of fact No. 4 raises an issue which must be heard.
5/
AIAB-463, 7 NRC 341, 360 (1978).
i
f 6
In the letter of Regional Director Kenneth E. Black of the Department of Interior's Fish and Wildlife Service to the NRC, dated March 15, 1978, he stated that Service personnel considered that inpact from siltation, as a result of the construction of the discharge diffuser, if located between Dixon Island and the upstream edge of the mussel bed "is anticipated ta be udnimal because construction of the diffuser portion of che discharge system is 6:Kpected to (re] quire approximately 6 nonths with dredging to be completed within a few weeks."/
6 i
l The Atomic Safety and Licensing Appeal Board observed in its 7/
l Decision of March 17, 1978 that:
j
... sedimentation, would be occasioned by dredging l
activities in the course of construction of the diffuser. The mussels are filter feeders, and although they can remave and dispose of a limited amount of sediment in the river, too much would cause tr n problems. The record is not clear as to how much is too ruch."
[ Footnotes omitted.]
It does not appear from any evidence offered in this matter, that there is available any precise answer to "how much is too much" on a quantitative basis. However, in the Opist m letter of the Fish and Wildlife Service, it is stated that because of the number of vari-ables involved in the construction of the diffuser and the operation 6]
Ex. 1 to Applicant's brief at p. 2, supra.
7/
AIAB-463, 7 NRC 341, 363 (1978).
7 of the plant "a systematic preproject and postproject nonitoring of the mussel beds, above and below the diffuser, should be initiated 8/
with the objective of determining if population changes occur...."-
The Board has reviewed the construction phase monitoring plan agreed upon in a meeting anong Staff, Intervenors, State of Tennessee, U. S. Fish and Wildlife, and the Applicant.-9/
The Board approves the plan with one change.
In item 6, Diffuser Excavation Period, if the mussels placed near the blasting zone are Lamosilis orbiculata, they should be renoved, examined, and returned inmediately to the river with care.
In addition, the Staff is to observe the diffuser dredging periodically to verify that the Applicant is adhering to +.ne noni-toring plan and that any accumulation of sediment on the mussel bed is acceptably small-10/
A report is to be prepared by the Staff after the dredging is completed and served on all parties to this proceeding.
The Board finds that, in view of the agreement of the parties as to nonitoring, there is no longer any genuine issue of fact to be heard as to TVA's statement of fact No. 4.
e 8_/ Ex. 1 to Applicant's brief at p. 3, suora.
-9/ Monitoring Plan for Mussels During Discharge Diffuser Construction
- Hartsville Nuclear Plants, enclosed with letter from Herbert Sanger, Jr., General Counsel, TVA, dated September 25, 1978.
A copy of the agreed to nonitoring plan (construction phase) is attached to this Decision as Attachment.
-10/ A representative of the U. S. Fish and Wildlife Service (WS) idll be present during the initial 2-3 days of dredging.
See the WS letter to TVA of October 27, 1978.
t 8
Proposed Statement of Fact Number 5 The record in this proceeding confirms the opinion of the Departcent of the Interior that the heated water discharged from the Hartsville Nuclear Plants during plant operation will not impact the mussel bed or fish in the area.
The Intervenors indicate that the above "is a statement as to which there is a genuine issue to be heard." In support of this n/
position, the Intervenors rely upon an affidavit in which it is stated that:
"The range of the proposed hosts for the glochidia of Lampsilis are very wide and not nearly as restricted as the mussel itself. This would suggest that factors other l
than glochidia host play the limiting role in the mussels range. The restricting factor may be in part temperature.
Further, the limited number of specimens and beds of the mussel suggest that Lampsilis is a delicate species. Small changes in a variety of environmental factors could affect survival. For example, a key factor in restricting range could be temperature.
If so, one would predict that shifts in tem3erature of the extent encountered from the discharge from tne proposed diffuser outflow may reduce survival ability of adults, of larvae, or otherwise reduce reproduc-tion potential of the species."
The Board, in its partial initial decision on environmental and site suitability aspects of the facility, indicated that:
"312.
Blowdown from the cooling towers will be discharged through a multiport diffuser into the Cumberland River. During low river flows the blowdown will be discharged to a holding pond which will enable 11/ Affidavit of Robert Jack Neff, dated June 7, 1978, suora.
9 the plant to operate at full power without violating the applicable thermal water quality standards."
[ Footnote omitted.]
and that:
"314. The Board finds that no significant adverse inpact will occur from operation of the heat dissipation system." 12/
However, the Board's partial initial decision was issued prior to the knowledge of the presence of the endangered species, Lamosilis orbiculata.
Pointing out that this Board was obligated to examine all possible adverse effects upon the species, in addition to resolving the issues in contention, the Appeal Board proceeded from the record established to make the following finding:
"... Danger from the increase in water tenperature is also unlikely. No matter which of the two alternate locations for the diffuser is used, it would be located on the deeper side of the river; as the mussel bed is on the shallower side, it will be outside of the mixing zone for the dis-charged water. The average tenperature rise outside that zone will be 1.6 F, and the maximum rise will be 3.3 F.
But because the discharged water will be forced upward by the angle of the pipes and the buoyance of the discharge, these higher temperatures should be found in the upper layers of the water and not on the river bottom where the mussels are. In any event, Lampsilis orbiculata is a warm-water species and the small increase in water tempera-ture, even should it occur at the level of the mussel bed, would not harm it.
For these reasons, we find that the endangered species would not be adversely affected by heat from the water discharged through the diffuser." 13/
[ Footnotes omitted.]
12/ 3 NRC 485, 550 (1976).
13/ A1AB-463, 7 NRC 341, 362 (1978).
B t
10 The Department of Interior Opinion letter states:
"The blowdown flow (thermal pollution) from the plant could have a temperature difference between the blowdown and river before mi.xing of -5* F. in October to 33 F. in March, averaging 16* F.
This thermal pollution could possibly affect the biological needs of the mussel and could present a thermal barrier for fish migration in this area. However, blowdown discharge through the diffuser is interlocked with flow from upstream dams and will be mi.xed with river water by jets. No thermal impact to the russel bed or to fish in the area is expected since the water temperature rise outside the mixing zone over the nussel oed would usually be less than 1* F., although it could be as high as 1.6* F.
The mixing zone is expected to be in the main channel across from the mussel bed. There should be little thermal influence of the fish fauna associated with the area of the mussel bed.
The mixing zone should occupy less than one-half of the width and depth of the main channel and should be no barrier for fish migration in this area." M/
Based on the record of this proceeding and after considering the Department of Interior Biological Opinion, the Board finds that the heated water discharged from the plant discharge diffuser during operation will not adversely affect the endangered species, and there-fore, there is not a genuine issue of material fact to be heard as to TVA's statement of fact No. 5.
Proposed Statenent of Fact Number 6 The record in this proceeding confirms the opinion of the Department of the Interior that the release of radiation from the Hartsville Nuclear Plants during routine operation will have no effect on the pink mucket pearly mussel.
14/ Ex. 1 to Applicant's brief at 2-3, suora.
I w..
11 In response, the Intervenors indicate that the above "is a statement as to which there is a genuine issue to be heard." In support the Intervenors provided an affidavit which indicates that:
2
"... An additional factor that could decide the survival of the species is the low level of routine emissions of radionuclides from the Hartsville Nuclear Plants. It nust be recalled that these organisms are filter feeders. As such they can be expected to show an extraordinary ability to concentrate radioactivity into their living body parts and shells. Thus, they may expose themselves in time to lethal doses of ionizing radiations." 15/
During the course of the construction permit evidentiary hear-ing, the Intervenors proposed and the Board admitted a new contention based on newly discovered evidence which indicated that:
The routine releases of radioactivity from normal operation of the proposed plants will harm certain mussel species found in the area proposed for the plant diffuser, namely Dromus dromas, Lampsilis orbiculata and Dysnomia sulcata.
Said releases have been underestimated by Applicant and NRC Staff.
Said releases will harm said mussel species in the following manner: by injuring or killing mussels of said species; annoying said species to such an extent as to significantly disrupt essential behavioral patterns, including breeding; and by causing significant environmental nodification or degradation, namely, the contamination of the sediment and waters of the Cumberland River." 16_/
The Department of Interior Biological Opinion indicates that:
... Because the potential radiological dose to benthic organisms in the river near the plant would be less than 1 nillirad per year compared to natural background radia-tion of 50 to 100 millirads per year, no effect to the pink nucket pearly mussel is expected." 17/
_15/ Affidavit of Robert Jack Neff, suora.
l_6/ 5 NRC 1081, 1107 (1977).
6 17/ Ex. 1 to Applicant's brief at 2, supra.
12 After considering the evidence in the record of this proceed-ing, the Board previously found that the radiological releases from the Plant will not produce significant adverse effects on the mussels 18/
in the Cumberland River."-
'Ihe information contained in the Affidavit of Robert Jack Neff does not cause the Board to alter its previous findings which were affirmed on appeal. Therefore, the Board finds no genuine issue of material fact to be heard as to TVA's statement of fact tb. 6.
Proposed Statement of Fact Number 7 The record in this proceeding confirms the opinion of the Department of the Interior that construction and operation of the discharge diffuser in the area between Dixon Island and the upstream end of the mussel bed is environmentally acceptable and will not jeopardize the continued existence of the pink mucket pearly mussel, L. orbiculata.
The Intervenors indicate that this is a statennnt as to which there is a genuine issue to be heard.
The Appeal Board, in AIAB-463, stated that "[o]nce informed that an endangered species lived in the vicinity of the plant, the Licensing Board was obligated to examine all possible adverse effects upon the species which might result from construction or operation of 19/
the plant and to make findings with respect to them."-
Noting that 138f 5 NRC 1081,1108 (1977).
H/ 7 NRC 341, 361 (1978).
13 the Licensing Board failed to make all of the requisite findings but had admitted evidence on the effects of operation, the Appeal Board was "... in a position to evaluate... [the evidence] and to make the findings ourselves." The Appeal Board then proceeded te make findings with respect to the operational effects of chlorine and thermal l
-~20/
discharges.
Furthermore, the Appeal Board agreed with the Licensing I
Board that the radiological releases during operation would not harm the lampsilis orbiculata.-21/
The Departnent of Interior Biological Opinion indicates that the "Possible impacts from the construction and operation of the diffuser, if located between Dixon Island and the upstream edge of the mussel bed, are siltation from dredge construc-tion, nortalities from blasting, and thermal and radiological pollution." 2_2_/
4 Even a casual reading of the Appeal Board Decision will.!orce the reader to conclude that the chlorine, thermal and radiological l
discharges were the only operational effects. The Appeal Board stated:
1
"... Accordingly, the only ram M ng Section 7 question with respect to the downstream location, Interior's approval of it having been obtained, is whether sedi-mentation from construction at that location would jeopardize the continued existence of the species." 23_/
20/ 7 NRC 341, 362 (1978).
21/ 7 NRC 341, 364 (1978).
1 22/ Ex. 1 to Applicant's brief at 2, supra.
23/ 7 NRC 341, 364 (1978).
14 and "However, we have found that operation of the plant will not cause any significant adverse effects upon the endangered mussels.
It follows that operation of the plant would not ' harm' the mussels within the meatung of 50 CFR 17.3 and therefore would not effect a taking of them within the meaning of Section 9 of the Act." -24/
[ Emphasis added.]
With var original finding on radiological discharges which was affirmed by the Appeal Board, and with the Appeal Board findings on the chlorine and thermal discharges, all the necessary findings have been made on the effects of operation upon lamsilis orbiculata.
Intervenors argued that amng other things the mnitoring pro-gram initially proposed by the Department of Interior was deficient in that it was limited to the preconstruction, construction, and postconstruction periods, but did not cover the time of operation of 21/
the plant.
Proposed modifications to the mnitoring program to 26/
cover the period of operation were made in an accompanying affidavit.
In reporting on the results of the successful negotiations amng the parties regarding an acceptable conitoring program during the diffuser construction, the Applicant argued that a mnitoring 2_4/ 7 NRC 341, 366 (1978), footnote 114.
4
-25/ Further Response of Intervenors, William N. Young, et al. to Applicant's Motion For Stumary Disposition on the Diicharge Diffuser location Issue, August 14, 1978, at 4-5.
26/ Affidavit accompanying Intervenors' further response to Appli-cant's mtion, supra, dated August 14, 1978, at 9-10.
15 program for the period during plant operation should not be adopted until nuch nearer to initial plant operation and that an operational monitoring plan is not an appropriate subject for a construction permit proceeding.-27/
In further pleadings, the Intervenors indicated that they do not contend that an operating license stage nonitoring plan should be fornulated or established at this time, but that this Board should impose as a condition on the construction of the diffuser, a require-ment of some mininun standards for a plan to monitor the impacts on the 28/
endangered nussels species of plant operation.-
As indicated previously, the record and findings in this con-struction permit proceeding clearly show that operation of the plant will not cause any significant adverse effects upon the endangered species of mussels. Therefore, this Board will not require as a con-dition for the construction of the discharge diffuser, a monitoring program of any format for the period of plant operation. However, the Board orders the NRC Staff to consider the protection of the endangered
-27/ Letter from Herbert Sanger, Jr., General Counsel, TVA, dated September 25, 1978.
-28/ Letter from Leroy J. Ellis, III, Counsel for Intervenors, dated September 27, 1978; Further Response of Intervenors to Applicant's Motion for Suamary Disposition on the Upstream Diffuser location, dated October 10, 1978.
L-
16 mussel species, Isosilis orbiculata, in developing the environmental technical specifications for the plant at the operating license stage.
l The effects of construction of the discharge diffuser in the area between Dixon Island and the upstream edge of the mussel bed have been discussed under Proposed Statement of Fact Numbers 3 and 4, above. Therein, the Board found that the construction of the discharge diffuser would not adversely affect the mussels.
Therefore, the record in this proceeding does confirm the opinion of the Department of Interior that construction of the dis-charge diffuser in the area between Dixon Island and the upstream end of the mussel bed is envinneentally acceptable and is not likely to jeopardize the continued existence of the pink mucket pearly mussel, Impsilis orbiculata. Further operation of the plant will not cause any significant adverse effects upon the endangered species of mussels.
Therefore, the Board finds there is not a genuine issue of material fact to be heard as to IVA's statement of fact No. 7.
l l
l
17 ORDER The Board finds that the filings in this proceeding, the depositions, answers to interrogatories, together with the statements of the parties and the affidavits, show that there is no genuine issue as to any material fact and that the Applicant is entitled, as a mat-ter of law, to a sumnry decision approving construction of the dis-charge diffuser at a point between Dixon Island and the upstream end of the mussel bed.
The NRC Staff is directed to incorporate the construction phase monitoring plan, which has been approved in this Decision On Ntion For Suamary Disposition, into any authorization issued to permit the construction of a discharge diffuser at a point in the Cumberland River between Dixon Island and the upstream end of the bed of endan-gered species of mussels, Lampsilis orbiculata. Further, the Staff is to observe the diffuser dredging periodically to verify that the nonitoring plan is being adhered to and that any accumulation of sedi-ment on the mussel bed is acceptably small.
C AND LICENSING BOARD b>H J. Venn Leeds,7Jr.
e gest J. Remick
%_ WA JA J6hh F. Wolf, Cha2.rman
// '
~
Dated at Bethesda, Maryland ff'
/
This 31st day of October 1978.
O e,
f,Cp *Wp' 7
gigggg h
k',,y 8/gA h MONITORDIG FLAN FOR MUSSELS DURDIG DISCHARGE DIFFUSER CONSTRUCTION - HARTSVILLE NUCLEAR PLANTS
/
This =onitoring plan has as a goal a co=plete assess =ent of the imp M.
of the construction of the Hartsville Nuclear Plants' discharge diffuser.
The keys to the environmental. monitoring plan for the diffuser construction are the decision points which have been devised for early feedback to assure integrity of the Dixon Island =ussel bed. Appropriate =1tigative actions to be taken during construction of the diffuser, should signifi-cant perturbations occur, have been incorporated into this plan.
I Special monitoring of the discharge diffuser construction vill include the following:
PPI-DIFFUSER CONSTRUCTION 1.
Square meter grid sa=ples vill be collected along approxi=ately 30 transects at 50-foot intervals approximating those established during the Dece=ber 1976 mussel survey. The number cf quadrats established on each transect will depend on the width of the =ussel bed at that particular transect. The square meter grid vill be placed on the botto= at approxi=ately 20-foot intervals and all =ussels vill be carefully re=oved and exa=ined and 4-ediately returned to the river.
This reassessment of the mussel bed prior to the initiation of diffuser construction is necessary because a visit to the Cu=berland River and Hartsville site in July 1977 revealed that mussels were being removed fro = the Dixon Island =ussel bed by co=nercial =ussel fisher =en. ATIACRET
'2.
Prior to the initiation of instream constntetion activities, sediments i
in the area of diffuser construction and downstream vill be sa= pled and characterized as to particle size and total volatile solids. This vill provide a baseline of data for evaluating the deposition of sediments resulting from the excavation activities. The following procedures vill be followed for this activity:
A.
Core sampler vill be utilized.
3.
Two transects vill be established at the site of dredging--10 sa=ples vill be taken.
C.
Three transects vill be established on the Dixon Island =ussel bed--15 sa=ples will be taken.
3 Chemical constituents of the sedi=ents vill be determined prior to the diffuser construction. An elutriate test vill be perfor=ed to detect any significant release of contaminants in the material to be dredged. Six sa=ples will be collected in the area to be dredged and 3 samples vill be collected on the Dixon Island =ussel bed.
Sa=ples will be analyzed for Hg, Pb, As, Cd, Cu, Zn.
4.
Sedimentation traps vill be placed by Scuba divers at specified intervals along the length of the Dixon Island mussel bed downstream of the proposed dredging operation to estimate the loss of and accumulation of materials in the sediments (to be continued throughout the instream dredging activities).
A control station (1 transect) upstream of the dredging operation vill be monitored to detect natural sedimentation rates for comparative purposes.
5.
Scuba divers will search the area from Dixon Island downstream to the upper edge of the Dixon Island mussel bed and remove any isolated mussel specimens. Any specimens found will be placed on or in the substrate of an established mussel bed. AITACHME27f
DIFFUSER EXCAVATION PERIOD 1.
Sedimentation traps will continue to be placed at the same stations used
)
in the prediffuser excavation period. The traps will be returned twice per eight-hour dredging crew working shift (once after four hours and once after eight hours) during excavation of approximately the first 1,000 cubic yards of material.
2.
Turbidity levels of the river above and below the dredging activities will be measured at 1-meter depth intervals from surface to the bottom and averaged over the water column to document changes in natural turbidity levels resulting f rom these activit.ies.
Samples vill be taken hourly during excavation. Natural turbidity levels of record as defined in the Hartsville Nuclear Plants ER will be the feedback criteria for regulating the rate of instream dredging. Maximum documented levels of turbidity are 85 ppm (JTU).
3.
Measurement of light intensity in the water column vill be perforced with a submarine photometer both above and below the dredging activities. Measurements vill be made hourly during excavation.
A 50 percent reduction in the depth of 0.1 percent of the light transmission at some selected point at the mussel bed relative to an upstream location (above the dredging activities) vill be the feedback criteria for instituting corrective mitigative acticas.
4.
Should turbidity levels or light penetration data indicate a need for citigative action, the inspector vill report his findings and make his reco=mendation to the project environmental engineer, who v111 present these findings and reco==endations to the project manager. The project =anager vill make the decision on the =itigative actions to be taken, i.e., to slow down or halt construction.
} AITACD M
o 5.
Dissolved oxy 6en, pH, conductivity, and te=perature profiles vill I
be made at upstrea= and downstrea= locations to document any perturbations of these parameters.
6.
During blasting activities, mussels vill be placed by Scuba divers at established intervals frc= the area of the blasting to detemine if mussels on the Dixon Island bed are har=ed by shock waves from these activities.
POST-DIFFUSER CONSTRUCTION 1.
A post-diffuser construction survey of sediments in the area of the
[
diffuser and =ussel bed vill be conducted to document any perturbation of river sediments as a result of these constniction activities. A total of 5 sa=ples vill be collected from each of three transects approxi=ating those established in Pre-diffuser construction (2).
2.
Transer +.s approxi=ating those established during the pre-diffuser construction survey vill be established at 50-foot intervals beginning at the upper end of the =ussel bed (CRM 284.1). ' Square neter sa=ples vill be taken along the transect. Mussels recovered from the square meter grids vill be carefully re=oved and exard.ned and i==ediately returned to the river. This qualitative and quantitative data vill serve as a reevaluation of the =ussels found on the Dixon Island mussel bed following completion of the diffuser construction activities.
The breeding season for La=ps111s orbiculata is reported to be during August and Septe=ber, with glochidia being discharged the following June.
Since =ussels are =uccid filter feeders, the increase in turbidity KITACOEE
4 dP l
levels should pose no problem to =ussels during any period of the year.
We therefore reco= mend that instream dredging activities associated with the discharge diffuser be conducted at any ti=e of the year.
- However, dredstng during the breeding season (August and Septe=ber) vill be avoided if possible.
8 ATLAGB E T
)
-