Lucas Vale", Brogo
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EIS 1036 ABO1 9735 An environmental impact statement for the quarrying and processing of Granodiorite and Basalt at "Lucas Vale", Brogo (supplementary report) (s /c.5 V, (S- 1k 019 735 cu - LUCA BrcDcQ N • - W - EN\T I RQN NT1L.I I 'IA'T EI'1ENT FcR TH QUPRR' I NG AN1D P HOcJE 3 I Nc c,Fr. 3RANQ]J I JR I T E AII1D 10.A L 'r (SUPPLEMENTARY REPORT) NSW DEPARTM MiNERAL RESOURCES 2 DEC 1994 LIBRAy COWMAN STODDART Pty1 Ltd1 TOWN PLANNING & ENVUIONMENfAL CONSULTANTS The Ilolt CenLre, Klnghorn Street, Nowra, N.S.W. LU< O V E Z ocz l'4 • 14 Vi 1 rr ri ri 1M r ri 't V C' V rt I4 V P44 V 44 (V U) '44 FAVi- A H ñ 0) o Z H 0 4- 44 '44 q4 ri 1144 J4 -1 LiZ ' 0 z o H Li 44 (V Vi Q. 1144 1.4 l( 44 'a) C' 14 Li T' Cl) 44 V -0 •• , Nj ' Lu H .J •- 1.4 V H 4-' Z • 4-4 C (V th C'44 •• OD 44 1.4 O r. b 0 r 0 I4 r 8E - - - - - - - - - - - - - - - - - - - - - I I cQrEr E I I 1.0 INTRODUCTION I 2.0 ARCHAEOLOGICAL STUDY 3.0 WATER AND SEDIMENT MANAGEMENT I 4.0 JUSTIFICATION FOR QUARRY I 5.0 SUPPLEMENTARY NOISE IMPACT ASSESSMENT 6.0 NOISE REDUCTION MEASURES I 7.0 VISUAL IMPACT I I .PFPENID I CES I Appendix A Letter from Department of Planning I Appendix B Archaeological report Appendix C Supplementary Noise Impact Report (including Noise Reduction Measures and details of I Berm location and dimensions). I I I I I I I I I I Page 4 1.0 INTRODUCTION I This Supplementary Report to the E.I.S has been prepared at the request of the Department of Planning and Bega Valley Council. I A number of issues were raised during the assessment of the proposed quarry which the Department felt had not been fully I addressed. As a result, additional studies were commissioned and the findings of those studies are reported in this Supplementary I Report. No attempt has been made to reproduce the contents of the original E.I.S and it is assumed that persons reading this I report will be familiar with the project. I I I I I I I I I I I I I I I Page 5 2.0 ARCHAEOLOGICAL STUDY I A preliminary study of the quarry site was conducted by Mr. 3ohn Hackwell in 1993 during which no archaeological sites I were located. The National Parks and Wildlife Service rejected Hackwell's report on the grounds it failed to meet the Service's minimum standards for archaeological reporting and I insufficient consultation was undertaken with the Bega Local Aboriginal Land Council. South East Archaeology was thereby requested to re-examine the proposed quarry site and prepare I a report to the standard required by the National Parks and Wildlife Service. The investigation proceeded by recourse to the Aboriginal and environmental background of the district, followed by consultation with the Bega Local Aboriginal Land I Council and a comprehensive field survey of the study area. No Aboriginal archaeological sites were located during the I current survey. The primary recommendation is that there are no archaeological constraints to the development proposal. I The report by South East Archaeology has been reprinted in full as Appendix B. Three copies were forwarded to the Regional Archaeologist of the National Parks and Wildlife Service on 7th February and one copy to the Bega Local I Aboriginal Land Council. I I I I I I I I I I Page 6 3.0 WATER AND SEDIMENT MANAGEMENT I As requested by the E.P.A. water pollution controls will be based on all water leaving the site passing through one of the sediment control dams to be constructed in the I depressions at either end of the quarry. Adequate storage will be provided for a 1 in 10 year 24 hour storm flow. I Calculations From Aust. Rainfall & Runoff. I Rainfall intensity for a 24 hour duration storm = 9 mm/hr. I =10 CPA = 10 x 0.35 x 9 x 24 x Catchment Area I = 756 x Catchment Area m3 The catchment area for the northern dam is 1.2 ha and the I southern dam 0.8 ha. Volume = 756 x 1.2 I = 907 m3 northern dam Volume = 756 x 0.8 I = 604 m3 southern dam Thus the required dam capacity to meet E.P.A requirements is I 907m3 for the northern dam with a catchment of 1.2 ha and 604m3 for the southern dam with a catchment of 0.8 ha. A diagram titled "Sediment Control Dam Capacities" is 1 attached from Caddey, Searl and Jarman, Registered Surveyors of Bega. This states, and illustrates, that dams could be physically constructed in these depressions with capacity of I 1,100 m3 (northern) and 660 m3 (southern). I NOTE: NO CERTIFICATION AS TO THE STRUCTURAL ADEQUACY OF THESE DAMS IS INTENDED OP IMPLIED. THESE DIAGRAMS ILLUSTRATE THAT DAMS CONSTRUCTED IN THE LOCATIONS SHOWN WOULD HAVE THE STATED CAPACITY. 80.00 /I . I II . I (J / I .79.27 \ \ \.79.O0 0 I._ 78.67 / 60 / , 80 .94 100 SOUTHERN SEDIMENT DAM NORTHERN SEDIMENT DAM Water Level = RL 76.0 OLYtQTt pQ Water Level = 1_1 -O4-1 Top of Darn Wall = RL 76.5 = RL 75.5 Top of Darn Wall Capacity to RL 76 = 1100rn3 DarnCapacity to RL 75 = 660rn3 Cdrnj-7t Avra -3ZQ--' hvriqvl Aa O•q - Wcr- ManaQ..rr7Q-7-f Pr) c Wa1r P10r7 Parish: MUMBULLA Scale: 1:500 CADDEY SEARL AND JARMAN Shire: SEGA VALLEY Drawn: GS SEDIMENT CONTROL DAM CONSULTING SURVEYORS AND VALUERS Locality: BROGO Surveyor: 10 CANNING STREET 60 MAIN STREET 4/2 WALLAGA ST. BERMAGUI Date: 21/01/1994 CAPACITIES BEGA NSW 2550 MERIMBULA NSW 2548 3/160 INLAY ST, EDEN Ref: 23872 Datuni: AHD PRONE:064-922933 PHONE: 064-951044 I Page 7 SOIL AND WATER MANAGEMENT PLAN I The catchment for the two dams have been reduced by the use of catch drains and diversion banks as shown on the attached Plan. "Clean" water now bypasses the quarry and sediment I dams and discharges from the diversion banks directly into the watercourse at the base of the hill. * Diversion Banks. The banks at R.L. 80 each have a catchment of less than I 1 ha and a length of 90 metres. Time of concentration = 10 minutes. I Rainfall intensity 10 minutes 5 year intensity = 105 mm/hr. Peak discharge q = CiA I 360 q = I 360 I = 0.12 m3/sec. Hydraulic radius a = q v I Bank cross sectional area = 0.12 0.55 I = 0.22 m2 For a 20 year return period a = 0.3 m2 I It is intended to construct the banks with a cross sectional area of 1.0 m2 which will provide a large safety margin against overtopping. The grade of the banks will be 0.25% to reduce I scouring in the channel and aid the deposition of coarse sediments. Sediment traps of 5 m3 capacity will be constructed at the ends I of each diversion bank, prior to runoff entering the sediment control dams. These will act as a stilling pond in which coarse sediments will be deposited prior to leaving the quarry site. I Their value will be in reducing the frequency of desilting the two main sediment control dams. I I I I Page 8 Water Supply Dam This is planned to have a capacity of 500 m3 and will supplement water supply from the Brogo River. It will be constructed at R.L. 100 in the northern depression above the I processing site. As shown on the plan, a diversion bank or catch drain around the top of the quarry will provide a water catchment for the I dam. The dam will have a long spillway bank following the contour on the northern side. Discharge from the spillway will be picked up by a second bank lower down the hillside I to ensure water bypasses the sediment control dam. In a similar manner a diversion bank will be constructed in the southern depression at R.L. 80 to prevent clean water I flowing into the sediment control dam as shown on the plan. Topsoil preservation Topsoil has an average depth of 100 mm across the site and will be conserved wherever possible. I This includes the site for the dams, the processing site and the quarry itself. The topsoil will be stockpiled on the quarry site immediately below the catch drain at R.L. 105. I Much of it will be re-used very quickly on critical areas such as dam batters. In any case all stockpiles will be I sown with a pasture mixture to prevent erosion. I 1 I I I I I I I © I L AN1D WAE' 1E R ]I?4E N 'r IP IN I NORTH I I TREE I PP I I I TREE OO I I I LT I I / 7 LEGEND I Sediment control dam R.L. 75 Diversion bank Stage I R.L. 95 Stage 2 R.L. 80 I Limit of extraction 4010000 Processing site I D RILL HOLES ' EDGE OF TREES Access road I PLAN SHOWING Berms CONTOURS & DETAIL Catch drain around I OVER PART OF top of quarry. 'LUCAS VALE S BROGO Diversion Bank. I Catchment ooundarv. I Water suprv darn.