Environmental Managemem Principal Office: Orher Office: ~j8tJOOl I and Engineering ConsultJnts 4Ib Tasma Srreet, North Hobart, Tas 7000 20 Rowmree Sneer GP.O BOj{ 659G, Hoban, Tas 700 I I:hJmain New Sourh Wales 2U41 Telephone: (002) jI ISOY Telephune: (02) 810 8 LOG I Facsimile: (002) 31 154~ Facsimile: (02) 810 5542 I ]011" MIEDECKc AND PARTNFRS PTY LTLJ I ACN. 002488 l28 I I I ;1 I I DRAFf I MICROFILMED I FICHE NO,O/Z'l4-.3- I CSR READYMIX SEVEN MILE BEACH ELA 29/89 I Preliminary I Environmental Management Plan I o.~ I July 1993 I I AMG REFERENCE POINTS ADDED I CSR READYMIX 7 MILE BEACH E.L. AERIAL PHOTOGRAPH OF THE AREA john miedecke and partners ply ILd date 15/Il192 Scale 1:25,000 I 984003 I CONTENTS I 1.0 INTRODUCTION 1 2.0 DESCRIPTION OF THE AREA 1 2.1 LOCATION AND ACCESS 1 I 2.2 GEOLOGY, TOPOGRAPHY AND DRAINAGE 1 2.3 GROUNDWATER 2 2.4 VEGETATION 3 I 2.5 LAND TENURE 4 2.6 EXPLORATION AND MINING TENURE 4 2.7 ZONING AND PLANNING SCHEME 4 I 2.8 LAND USE AND HISTORY 5 2.9 FUTURE USE AND MANAGEMENT I PLANNING 6 3.0 EXPLORATION AND FUTURE SAND EXTRACTION 7 3.1 POTENTIAL RESOURCE 7 I 3.2 EXPLORATION PROGRAMME 7 3.3 FUTURE SAND EXTRACTION 8 4.0 ENVIRONMENTAL ISSUES AND MANAGEMENT 8 I 4.1 INTRODUCTION 8 4.2 FUTURE SAND SUPPLIES FOR HOBART DISTRICT 9 I 4.3 ISSUES 10 4.4 DEVELOPMENT APPROVALS 13 I 4.5 REHABILITATION 16 I I I I I I I I I I CSR Readymix - Seven Mile Beach Exploration Area· Prenminary EMP I 1.0 INTRODUCTION CSR Readymix have applied for an exploration licence from Mineral Resources Tasmania for an area of 2 square kilometres at the eastern end of I the Seven Mile Beach Protected Area. Other Government and local government bodies have indicated a number of concerns which would have to be addressed if a sand extraction operation could proceed, including I possible land use conflicts with the proposed recreation uses of the area. It is also anticipated that the granting of a exploration licence and the pUblic advertisement will result in interest from local residents, resident groups. and I other members of the public with interests in the area. As a result, the Director of Mines will not recommend the issue of an I exploration licence until he is satisfied that these concerns have been addressed in the form of an environmental management plan, although at I this stage it can only be conceptual. This report has been prepared for the Company and addresses the concerns and issues which have been raised by other government agencies and those which can be anticipated from the public in the experience of the I Consultants. It outlines a proposal to explore for, and if feasible, to recover I sand from the proposed Exploration Licence Area. 2.0 DESCRIPTION OF THE AREA I 2.1 LOCATION AND ACCESS Seven Mile Beach is the southern coastline of a sand spit separating I Frederick Henry Bay from Pitt Water ( see Figure 1). It is also the name of the proclaimed Protected Areas (about 11 square kilometres) and of the I township at the southwesterly end of the beach. Access to the area is by way of Pitt Water Road, which joins the Tasman Highway 2 kilometres east of the entrance to Hobart airport. The road I junction lies about 20 kilometres east of the Tasman Bridge over the Derwent River. The access road is sealed, in good condition with ample width and available land for any upgrading. There are no residences in I close proximity to the road, and only two (a farm house and the Rangers house) in the area. I 2.2 GEOLOGY, TOPOGRAPHY AND DRAINAGE The spit is composed of Quaternary sand to an average depth of 13m below I sea level, overlying Tertiary clay. The spit is thought to have been formed almost entirely in the Holocene, apart from a small remnant of Last Interglacial sediments at the northern end of the airport runway, adjacent to the Tasman Highway. The Dune system has probably developed from wave I built beach berms that were formed successively on sandy shores, and were stabilized into large dunes by vegetation growth. I The present sand spit is composed of about fifty sand beach ridges aligned approximately parallel to the southern shoreline. Dune heights vary from I john miedecke and partners ply ttd July 1993 I TASMANlA 1 : 25 000 SERIES • • CARL . u " SOREll 21 • • • • .• prrr WATER ..... m .. ­ r- • TOWN - aJ ·,!----><.-+--==~k+_f_---_+_---_1----_+l__----=;T--'=::::-~-----HQ~~~~-!~~~ ,/ '< FIGURE 1 III -CD CSR READYMIX 7 MILE BEACH E.L. 3 LOCATION PLAN ·000 miedecke and artners ltd JI~=~~------l-+----+-+-----I 5cm FREDERICK HENRY 984006 I CSR Readymix - Seven Mile Beach Exploration Area - Preliminary EMP 2 one to six metres, with an average height of about three metres. Dune I heights decrease from west to east along the beach due to a reduction in energy of the refracted swell. During the last century, erosion of the eastern end of the beach has been balanced by progradation of the central part. I However, the frontal (primary) dunes are the most developed (widest) in the eastern area. Behind the frontal dunes is an area of gentle topography which extend to Pitt Water. Figure 2 shows a typical cross section through I the dunes. They can also be seen on the aerial photograph in the frontispiece of the this report. I There is little or no surface drainage in the Exploration area because of the direct infiltration of any rainfall, which percolates through the sands to the I groundwater table. 2.3 GROUNDWATER I Groundwater has been investigated in the area by the Department of Mines (Cromer and Sloane (1976), The Hydrology of Seven Mile Beach. Department of Mines unpublished Report No 1976/10). These investigations I were confined to the central area of the beach. The groundwater body assumes a tabular form 10-12 metres thick with its upper surface slightly convex. The water table is generally independent of I the topography. Relative to mean sea level (MSL), the groundwater body displays a gently convex surface, attaining a maximum height of about 2.5 metres above sea level over the area investigated. Hydraulic gradients in I the order of 0.0025 metres per linear metre exist seawards and towards Pitt Water. The gradients increase sharply near the high water mark and are I strongly influenced by tidal effects. The base of the body corresponds to the Quaternaryl Tertiary boundary, where the Tertiary Clay acts as an effective aquiclude. Near Pitt Water and I along Seven Mile Beach, the groundwater maintains a virtual hydrostatic equilibrium with seawater. The freshwater/saltwater interface is expected to be in the form of a wedge, with salt water dipping beneath the fresh water I near the high water mark. This has implications for water extraction as over exploitation may result in salt water incursion. I There are lateral and vertical variations in quality and it is estimated that there is a safe yield of ground water between 1 to 1.7 million cubic metres (m 3) with a total dissolved solids content of less than 1000 ppm in the I unconfined aquifer to a depth of 14m. This ignores the eastern third of the beach (I.e the ELA area) and the airport). The water is suitable for agriculture but not generally for domestic consumption. Cromer and Sloane I suggest that it is acceptable for domestic use if tapped from shallow wells or spear bores and not closer than 300m to the coast. There is also saline groundwater in a semi-confined aquifer below 14m which is unsuitable for I domestic, agriculture or livestock. Cromer and Sloane assumed 30% of the rainfall ( 550mm per year) percolates annually to the water table. Such yearly additions therefore, I represent about 10% of the storage of the aquifer. It is also important to recognise that the vegetation cover has a marked effect on infiltration and I john miedecke and partners pty ltd July 1993 I 984007 . 11, .. ~ .,. .~. FIGURE 2 CSR READYMIX 7 MILE BEAC,H E.L. Wb. ~ CROSS SECTIONS .. 1/ '--- _ "~M ,.L..c:::::======~======~_--,-- ~== johnmiedecke and partners pty ltd __ Scale Vert 1:2000, Horiz 1:10,000 _'1 _ "] ~--- ~:r c:---J.-------~ ::\1 1 .-=-~~-::::::::-=-=-=-=-=-=-=-=-=-=-===~--~:.,..;.,--- ~~"t ---.--======-:::::>-,=----.:::::.-J -II ----------------'----------- I~ --::::::~==================I .w:L_c=III ::_=-==-=-==..f"..-_.:::-=-=-=-=-=-==-:::::--------~-1__::::::::.., ~~'It.LL:::==================:::=::================:::::::-::=>"~-=== -,1----------------------- =="J EL 29/89 ,0 1 ·"~M [~L-=-=-_-=s=..:=-=-_-=-=-:=-=-:=-=-_-=-=-_-=-=-_---=~_-=-=-_--'=-=-_-=-=-:=-=-_-=-=-r-_=-:::_1-----===-=.-=-_-=-=-~=-=-:=-=-_ -=-=-:=-=-_-=...........:~ EL 20/89 ~ 'lICLLL::::=:=========================::::::::::.--=:::=========~»J .. I.~ ~_,....::-e::::=.._---------------------____'!' -4' :-4 5cm 984008 I CSR Readymix - Seven Mile Beach Exploration Area - Preliminary EMP 3 that pines (Radiata), are very effective water users. Such vegetation cover I will therefore have a marked effect on the aquifer recharge. I 2.4 VEGETATION The EL area is composed of a segment of the entire cross section of a dune system extending from Seven Mile Beach to Five Mile Beach. For the I purposes of this report it can be separated into two elements; The southern section which composes approximately one third of the I area, includes a series of sand ridges and hollows known as swales of complex topography. I Behind this are the dune slacks, flat ground which extends to the beach on the leeward side of the sandspit. I The introduced marram grass (Ammophila arenaria) forms the dominant cover on the dunes mostly out-competing native dune stabilising grasses although Poa poiformis is present.