GEOLOGICAL ASSESSMENT FOR COMMERICIAL SAND AND GRAVEL (CSAG)

PERMIT APPLIED BY NIÑO C. OSICO

1. Introduction

In relation to the Environmental Management Bureau (EMB) Memorandum

Circular (MC) 2020-27 issued on June 17, 2020, the application for the Non-
metallic Resources applying for Environmental Compliance Certificate (ECC)
shall submit a Geological Assessment of the resources available in the river.

The geological assessment will determine if the area is feasible for the Sand
and Gravel extraction. The assessment’s purpose is to ensure that the
extraction is carried out in a sustainable way, and maintain the equilibrium with
the application of sediment transport.

Hence, the Commercial Sand and Gravel (CSAG) proposed area of Mr. Niño C.
Osico located at Simulao River, Barangay San Ignacio, Trento, Agusan del Sur
having an area of 50,000 square meters was subjected to Geological
Assessment.

2. Site Conditions

2.1 Site Description and Accessibility

The proposed site for Commercial Sand and Gravel (CSAG) Permit of Mr. Niño
C. Osico is within the Municipality of Trento, a 1st class Municipality of Agusan
del Sur. The proposed site for CSAG is located at Simulao River in Barangay
San Ignacio containing an area of 50,000 square meters. It has an aerial
distance of approximately 8.78 kilometers east from the Municipality Hall of
Trento. The project site can be reached using the Barangay Road with travel
time of about 15minutes from the Municipal Hall.
(see figure 1).

Figure 1. Location Map of the Project site using Google Earth Pro.
 TECHNICAL DESCRIPTION
(PRS 1992 Projection)
Corner Latitude Longitude

1 7º59’ 32.676” 126º08’ 53.786”

2 7º59’ 30.946” 126º08’ 55.276”

3 7º59’ 29.646” 126º08’ 58.606”

4 7º59’ 31.166” 126º09’ 05.136”

5 7º59’ 26.776” 126º09’ 06.496”

6 7º59’ 26.962” 126º09’ 22.796”

7 7º59’ 28.416” 126º09’ 00.239”

8 7º59’ 31.436” 126º08’ 55.286”

2.2 Topography and Drainage

The proposed area for Commercial Sand and Gravel (CSAG) permit is
within the Simulao River. It is a tributary of the well-known Agusan River
which flows from Compostela Valley in the south towards Agusan del
Norte.

Based on the topographic map below, the applied area situates at a very
lowly elevated area in Trento ranging from 20-76 meters above mean
sea level (see figure 2).
2

Figure 2. Topographic Map of Trento, Agusan del Sur (https://en-ph.topographic

map.com/maps/otf7/Trento/)
2.3 Climate

The Municipality of Trento is under Type II on the Modified Corona’s

Classification of Philippine Climate, there is no definite dry season and very
pronounced rainfall from November to April (See figure 3).

Figure 3. Modified Corona’s classification of Philippine Climate Map

2.4 Regional Geology

The area is generally within the Agusan-Davao Basin, underlain by Wawa

Formation. Exposures was observed on the Wawa River in Prosperidad. The
Wawa River Separates the Agdawan Formation with an angular unconformity
during early to late Pleistocene (NN19) from the folded late Miocene to late
Pliocene (NN15-16) beds.

The Wawa Formation is composed of Lower Sandstone and upper Carbonate

member ranges from Early Pleistocene to Late Pleistocene, while traces of
Adgawan Formation have been exposed in the western coast of Butuan Bay to
the west of Davao Gulf (BED, 1986b). A section at the Las Nieves Anticline
revealing a clastic series with a lower turbiditic portion and an upper
conglomeratic portion of Adgawan Formation (Pena, 2008).

Locally, the project site is Quaternary Alluvium composed of mostly of volcanic

rocks (see figure 4-5). There were no outcrops observed within and on the
surrounding area.
 Figure 4. Stratigraphic Map and Column of Agusan-Davao Basin

Figure 5. Cobble and pebble sized sediments found at the proposed site for
Commercial Sand and Gravel Permit.

2.5 Geological Hazards

Based on the generated map of the Mine and Geosciences Bureau (MGB) 13,
the Commercial Sand and Gravel (CSAG) area lies under the Very High Flood
Susceptibility and surrounded by Moderate Susceptible to Landslides. As per
field interview, there were no record of landslides. However, if movement of land
mass/soil creep is observed, it is recommended to report immediately to the
disaster risk office in the municipality to conduct precautionary measure and
further study on the area (see figure 6).
Figure 6. Detailed Landslide and Flood Hazard Map generated by Mines and Geosciences Bureau, Region 13 (2015).

3. Sand and gravel Sand and Gravel Deposits

Sand and gravel are naturally occurring deposits on the rivers thru geologic
processes. These sand and gravel can be used for base on construction or can
be used as flexible pavements.

Sand and gravel can be igneous, sedimentary or metamorphic rocks. The

materials present on the proposed area determine the rocks present on
upstream and in situ. The classification of rocks helps decide excellent source
of sand and gravel for road construction, mixing asphalt, construction fill,
production of construction materials like concrete blocks, brikes, pipes, etc.

4. Sand and Gravel Assessment

4.1 Potential Sand and Gravel sources

Field assessment revealed that the quaternary alluvium deposits are composed
mostly of volcanic and fragments of plutonic rocks such as diorites
 6
(see figure 5). The table below shows the physical properties and observations
on the field:

Physical Property Observations

Rock Classification Volcanic (andesites)

Particle Size Cobble and pebble (Wentworth

Classification of Sizes)

Particle Shape Subrounded, Angular

Weathering Slightly weathered

4.2 Resource Estimation

The volume estimation is based only on the current surficial deposits in the area.
The available sand and gravel resources is based on the Commercial Sand and
Gravel area, which contains 50,000 square meters multiplied by an estimation
of 1.0-meter thickness alluvial deposits.

Estimated Volume = Area x Thickness

The estimated volume of the applied area is 50,000 cubic meters composed
mostly of volcanic rocks and fragments of plutonic rocks.

4.3 Replenishment Rate

Replenishment rate on rivers is required in order to observe the adverse impacts

arising due to excessing sand and gravel extraction. The excavation does have
impacts on the physical characteristics of the river, bed elevation, flow velocity,
discharge capacity, sediment transport capacity, and turbidity.

Monitoring in local mining sites for replenishment needs entire monitoring

throughout the estuary during a cumulative response of the system to sand and
gravel extraction. The riverbed’s elevation is variable from year to year; a reach-
based approach to monitoring will provide a larger context for site specific
changes.

The replenishment rate study in the Simulao River has not yet accomplished
yet since it needs an allocated time during dry and wet season,
absence/presence of extraction on the upstream and downstream. However,
based on the observations on the field, sediments replenished during flood
events evident by flood debris accumulation that can be seen in the depositional
section of the river during after heavy rain flow. It was also observed that the
project site has enough deposits for sand and gravel extraction.
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5. Summary

∙ The area for Commercial Sand and Gravel (CSAG) survey is limited only to the
physical characteristics of the alluvial deposits found within the applied area;

∙ The proposed site for Commercial Sand and Gravel (CSAG) Permit is situated at a
Very High Susceptible to flood classification and moderately susceptible to
landslide based on the MGB-13 Geohazard Map and observations during the
assessment. There was no record of landslides in the area;

∙ The quaternary alluvial deposits found within the applied area are mostly volcanic
rocks and fragments of plutonic rocks with cobble and pebble sized sediments. The
rock classification determines the rock on upstream and in situ. There were no
outcrops observed within/near the applied area;

∙ The thickness is projected only up to 1.0 meter from the surface. The calculated in
situ resources is approximately 50,000 cubic meters;

∙ The Replenishment rate has not yet accomplished due to lack of data and
timeframe. However, based on the field observations the sediments on the
proposed site replenished during flood events evident by flood debris
accumulation that can be seen in the depositional section of the river and on
the river channel which indicates that the area has enough deposit for sand
and gravel operations.

6. Recommendation

The area does have extractable materials of 50,000 cubic meters and limited
only up to 1.0 meter depth. It is recommended to put a cobble sized materials
on the east and west bank on the proposed site to avoid abrupt erosion of banks
and maintain river course. LGU’s and other concerned agencies must conduct
annual monitoring on the sand and gravel materials present in the area if it still
have sufficient deposits. If soil creep/mass movements was observed in the
surrounding area, it is recommended to report immediately to the Disaster Risk
Office in the Municipality to have a precautionary measures and conduct
further study.

Prepared by:

Gerome L. Amper
Consultant Mining Engineer
License No: 0003108
PTR No. BC2015696
REFERENCES

Agusan del Sur School of Arts and Trades. (2014). Agusan del Sur Profile. Retrieved
from https://sites.google.com/a/tesda.gov.ph/assat/province-profile-1

Department of Irrigation and Drainage. (2009). River Sand Mining Management

Guideline. Retrived from
https://www.engr.colostate.edu/~pierre/ce_old/classes/ce717/Sand%20minin
g.pdf

Minerals Education Coalition. (2020). Sand and Gravel. Retrieved from

https://mineralseducationcoalition.org/minerals-database/sand-and
gravel/#:~:text=Sand%20and%20gravel%20are%20used,railroad%20ballas
t %2C%20and%20water%20filtration.

Peña, R.E. (2009). Lexicon of Philippines Stratigraphy 2008.

Smalley, M.L., et. al. (1994). Annual Replenishment of Bed Mineral by Sediment
Transport in the Wind River Near Riverton, Wyoming. Retreived from
https://pubs.usgs.gov/wri/1994/4007/report.pdf

Topographic-map.com. (2020). Trento. Retrived from https://en-ph.topographic

map.com/maps/otf7/Trento/

Asian Development Bank (2004). Technical Assistance to the Republic of the

Philippines for the Master Plan for the Agusan River Basin. Retrieved from
https://www.adb.org/sites/default/files/project-document/69512/tar-phi
36540.pdf

Mines and Geosciences Bureau, Region 13 (2015). Detailed Landslide and Flood
Hazard Map of Trento, Agusan del Sur, Philippines 4217-III-23 Cebolin
Quadrangle
ATTACHMENTS

Sketch Plan of Mr. Niño C. Osico for the Commercial Sand and Gravel Permit.