Baseline Data

2. Baseline Data

Before mining, Sepapah area was covered by local tree species such as gelam tikus (Eurya accuminata), Somea, Wawangon, Seriberangkat and shrub species scuh as damar tingkir (Shorea beccariana), Bangkirai (Shorea sp). Areal eks PT INHUTANI II was dominated by gelam tikus (Eurya accuminata) and open land owned by community many local trees found such as coffee, sungkai (Peronema canescens), cempedak (Arthocarpus integer), laban (Vitex pinnata) dan durian (Durio zibethinus).

The majority of soil (97 %) at Sepapah is Ultisol (Podzolik) and the remaining (1,03%) Inceptisol dan (1,88%) Entisol. The soil had a shallow solum with fraction such as gravel, iron concretion and plintit about 15 to 50 %.

Premining condition, average bulk density at the surface 0-15 cm was 1,25g/cm 3 , at depth 15-30 cm was 1,46g/cm 3 and increased to 1,60g/cm 3 at depth 30 -60 cm. Soil porosity at the average of 44,8% at 15-30 cm and 29,4% at depth 30 -60 cm indicating that roots growth was limited to the depth 60 cm. Infiltration rate at undisturbed area varied from very slow (0,28 cm/jam) to fast (18,78 cm/jam) whereas soil permeability (K) generally fast to very fast due to the presence of gravel and sand as well as extensive root system.

Soil fertility was low as evidenced by its soil pH, base availability and saturation, CEC and its organic content thus its value for each of those parameter was low except Al saturation medium to very high. Average acidity of the upper 15 cm was low 4,30-5,7 but increased with dept up to 4,7 - 5,10. Organic Carbon and total Nitrogen was found to be high at the surface but decrease with depth. Base saturation level was low however Aluminium saturation high to medium which may harm the root growth.

Cation exchange capacity (CEC) and the ability of soil to retain water was also low. ESP value indicating the presence of sodium in the soil ranged within the acceptable level and electrical conductivity showing the osmotic pressure of soil solution was in the safe level. Availability of Cu and Zn was considered to be low, however Fe and Mn high associated with high FeO in the soil.

During wet season especially December till June, rainfall was mostly higher than 200 mm. Considering the area cleared and sediment ratio of 0,25 the total sediment expected to be washed down from outlet F-G in 1999 approximately 614,1 ton or about 470 m3 (PT. Arutmin Indonesia 1999). Due to erosion rate and changed hydrological system, total suspended solid increased significantly (1146 - 6876%) from the premining condition (PT Arutmin Indonesia 1999).

Before mining, water temperature ranged from 25-28,3 oC, total dissolved solid 15-1410 mg/l (the threshold at that time 1500 mg/l) and turbidity 4,2-24 nTU. Environmental impact analysis study showed an increased in suspended solid at downstream of Sepapah River due to the presence of domestic activity (agriculture and housing) and logging at the upstream of Sepapah River. Water quality of several parameter was found to be higher than allowed threshold such as pH (5 -7,8). This condition shows a characteristic of natural Kalimantan which to have a relatively low pH. Other water quality also showed a trend of increase from 1996 to 1998 due to logging activity.

Samples of 66 overburden from 8 drill holes were collected in 1996 to determine the geochemical characteristics of the overburden. The sulphur content of the majority of the overburden samples is relatively low with 53 samples of the 66 (80%) having a total sulphur content of less less than 0,5 %.

The acid neutralizing capacity (ANC) for all of the overburden and interburden ranges from very low to high (0 - 143 kg H2SO4/ton) with about 46 % having ANC greater than 20 kg H2SO4/ton).

Of the 66 samples tested, about 20 % (13 samples) have a positive calculated net acid producing potential (NAPP) value and the remaining samples have a negative of zero calculated net acid producing potential (NAPP). Six of the 13 positive NAPP have a NAPP value less than 10 kg/H2SO4 and therefore have only low capacity to produce acid. Seven samples of the 13 positive NAPP have a NAPP value greater than 10 kg/H2SO4 and therefore may represent higher capacity or higher risk material.