Observers like to comment that in its bid to become industrialized, environment concerns took a back seat to business priorities in Mandaue City. Surprisingly, it is only in Mandaue where one will find multi-sectoral groups constructively working together to balance environment, community and business interests.
There is the multi-sectoral Butuanon River rehabilitation effort initiated in 1996. In June this year, over 400 volunteers from the city government, barangay residents (including squatters), schools, and businesses along Tipolo Creek joined hands to clean-up the polluted waterway in anticipation of the rainy season. Another multi-sectoral group is diligently working to come up with a win-win solution to the conflicting environment, community, and business interests -- this is the sinkhole ad hoc committee. In this instance, even the City Engineer's Office of Cebu is actively participating in hammering out solutions.
Other members of this committee represent the Mandaue City government, Progeny Development Corp., Metro Cebu Water District, San Miguel Corporation, Mandaue Chamber of Commerce & Industry, Sto. Nino Village Homeowners Inc., the University of San Carlos Water Resource Center, and the Department of Environment & Natural Resources.
The center of so much heated discussion and arguments is the "bito" or sinkhole located within the property of Progeny in Barangay Cabancalan. This area, about 15 hectares including Progeny's 6.9 ha. property, is often flooded during rainy season owing to its low elevation. It serves as a natural catch basin for the Banilad-Talamban-Cabancalan neighborhood, with the sinkhole as drain. The flood plain where the sinkhole is situated also includes Sto. Nino Village. During rainy season the subdivision becomes a funnel through which the storm run-offs from the elevated subdivisions, residences and establishments pass through before the floodwaters are drained in the sinkhole through a 600-meter drainage system that Sto. Nino installed. This same drainage system transports the domestic wastes -- both solid and liquid -- to the sinkhole.
One camp argued that the sinkhole is a feature of a recharge area, and therefore, only stormwater should be allowed into it. Water resources experts from San Miguel Corporation and the Metro Cebu Water District warn that permitting untreated wastewater and solid wastes into the sinkhole will contaminate the groundwater supply. Over 90% of Metro Cebu's water supply is from groundwater resources.
The other camp preferred to regard the sinkhole solely as a natural drainage system. Rehabilitating it will help address the flooding problem in the area. Engineers from Progeny, thecity governments of Mandaue and Cebu, and Sto. Nino Village argue that while the bito was still functioning, floodwaters in the sinkhole and the area subside in a matter of hours or days. When the sinkhole became clogged with garbage and sediments, the floodwaters stayed for weeks and months, becoming stagnant.
In the ensuing meetings and consultations different experts were brought in. San Miguel Corporation flew in its water resources manager from Manila. Progeny did the same for their consultant, a flood control expert. Not to be outdone are the residents of Sto. Nino and barangay Cabancalan who are most familiar with the flood pattern in the area. It was inevitable that having different agenda, the ad hoc committee members clashed on almost everything.
WHAT IS A SINKHOLE?
A sinkhole is a funnel-shaped hole that connects to natural underground tunnels. These natural formations, the sinkhole and underground channels, usually occur in limestone regions. These are formed as a result of the chemical action of water on a soluble carbonate rock like limestone.
Residents fondly refer to it as "bito" in the vernacular. This bito has been around even before the war. Pepe Remedio, a local resident, claims that about 60 years ago he accompanied his father in conducting a dye test to determine where the sinkhole leads. According to his father, the dye came out of the Jagobiao spring in Consolacion, about a kilometer away. Other residents and old-timers support this theory because whenever it rained in Banilad-Talamban-Cabancalan, the water that comes out of the Jagobiao spring is muddy. Another unverified story is that during the war, the Americans blasted the sinkhole or one of the underground tunnels to prevent the Japanese from poisoning the Jagobiao spring.
The Osmena Waterworks System and MCWD tapped this spring for their water station which produced 4,000 cu.m daily until the spring dried up in 1982. In mid-80's MCWD also hired a consultant to perform a dye test but it failed to prove or disprove the Jagobiao theory.
Silvestra Oplado, another old-timer in Cabancalan, added that the residents who tilled the rice fields nearby always maintained the sinkhole for irrigation and drainage. The rice fields have since been subdivided into residential lots, replaced by a kangkong "plantation" that has thrived in this water-logged area.
The performance of the sinkhole as drain also changed over the years. Residents say that water usually stays in the flood plain for a couple of days only until it is absorbed, but later it took weeks and months for the area to dry up. This is probably because the continuing residential and commercial development in Banilad and Talamban increased the volume of storm run-off. It is estimated that the storm run-off that floods Sto. Nino carry about 35,000 cubic meters of water from a 300-ha. area in the neighborhood. There is no separate drainage system for regular household wastewater and stormwater. Exacerbating the situation was the presence of garbage and other solid waste in the drainage system.
Sinkhole experts say that it is normal for sinkholes to become blocked over time, usually by silt and sediments. In this case, however, the solid waste not only clogged the sinkhole, it also poses the danger of contaminating the groundwater supply. The bito taskforce organized by the committee to clean the sinkhole found a rubber tire, a wooden cart, and live fish amidst the garbage and muck that they dug up. The sinkhole is about six meters wide at the mouth, and six meters deep although the taskforce doing the manual digging has not reached the bottom yet.
SEAL THE SINKHOLE
Sinkholes generally connect or lead to the groundwater thru cracks and underground tunnels (solution channels). Thus, sinkholes transport water faster and with minimal filtration compared to water that is absorbed from the surface through layers of clay and limestone. If this water is polluted, the contamination of the groundwater will travel for miles through the permeable limestone aquifer. Once contaminated, the adverse effects are irreversible. For as long as the sinkhole is open the threat remains. Protecting, maintaining and occasionally de-clogging it require vigilance and resources. Sealing the sinkhole is the best guarantee against the threat of contamination.
RECHARGE AREA
The Banilad-Talamban-Cabancalan area itself is abundant in groundwater supply. SMC and MCWD operate deepwells here. The presence of fissures in the ground, as well as the conspicuous green vegetation cover throughout the El Nino drought period suggests that "a constant supply of groundwater, not far below the ground, is available to the plants." This 15-hectare flood plain is regarded as recharge area that replenishes the groundwater supply of Mandaue City by MCWD.
Progeny asserted that the area is "water-logged" or flood-prone but is not a recharge area. They point out to the slow absorption or infiltration of the floodwaters, and likewise to the presence of kangkong swamps and stagnant waters. Progeny's bore tests also showed that the ground below is made of clay which is less permeable than limestone, which would explain why the surface water takes time to be absorbed into the ground.
SMC, MCWD and WRC -- familiar with studies on the characteristics of Cebu's limestone aquifer -- disputed these arguments citing that the mouth and walls of the 6 meter deep sinkhole are made of limestone. WRC added that the fact the floodwater eventually disappears means these are absorbed. SMC and MCWD referred to the volume of water in their deepwells, and the shallow wells in the vicinity which were hardly affected by the drought.
TO DEVELOP OR NOT TO DEVELOP
If the 15-ha. area is a natural catch basin or flood plain then we should let it be, so it will serve its purpose: absorb the floodwaters and recharge the aquifer.
Progeny is establishing a commercial subdivision with 40 warehouses. What happens then if the other lot owners follow the lead of Progeny in backfilling and developing the entire area? Where will the floodwaters go? Answer: to the remaining low-lying areas which are Sto. Nino Village, the drainage system, and other waterways. Thus, we are only diverting the floodwaters and transferring the problem elsewhere, but meanwhile, the recharge capacity of the area is diminished by the development.
What is the implication or impact of this to the groundwater supply? Answer: Water tables are usually close to the surface if the area is a recharge area, and therefore accessible to shallow wells. Reducing the absorption capacity of that area will therefore lower the water table and possibly dry up the shallow private wells of households and small businesses.
How much development can the area absorb? Considering that two other sinkholes have been found in the vicinity, this suggests that these sinkholes are linked to solution channels or underground tunnels. A house or building constructed above would have a weak foundation because everytime it rains water will travel through these solution channels.
FLOODING
Councilor Carlo Fortuna, the chairman of the sinkhole ad hoc committee, wondered if Nature designed that low-lying area to be a catch basin to recharge the aquifer, wouldn't it be better not to tamper with it? Why not just let the floodwaters settle there for a few days, after all, it is eventually absorbed?
Progeny raised the risks of water-borne diseases and dengue if the flooding and drainage issues are not addressed. Sto. Nino have already spent much for the expansion, rehabilitation, and maintenance of their own drainage system just to accommodate the wastewater and storm run-off in that neighborhood.
MCWD would also like to leave the 15-ha. area open to accommodate stormwater. If the area is developed, the recharge capacity is drastically reduced since the rain water that falls into the roofs, pavement, and gutters are diverted to the drainage.
DRAINAGE SYSTEM
Progeny initially proposed a drainage system that connects with the existing city drainage in M.L. Quezon Ave. The company has already backfilled their property to elevate it by 1.5 meters, which is about the same level as MLQ. Their proposed drainage system is half a meter higher than the mouth of the sinkhole. Thus, their drainage system will accommodate only the excess floodwater from Sto. Nino if the water level reaches 0.5 m.
SMC, MCWD, Sto Nino and some residents of Cabancalan feared that this drainage design will cause a backflow. Both MLQ and Progeny are higher than the sinkhole area. The culverts of Progeny are equal or bigger than those in MLQ (36" and 48"). The drainage system in MLQ was designed to accommodate only the run-off from that street. Thus, the floodwater in MLQ might even backflow into the Progeny drainage system and drain into the sinkhole area. In short, the volume of floodwater is increased while the land area is reduced.
Progeny presented another drainage proposal -- install a lower drainage system that will drain into the Butuanon River, the only waterway lower than the sinkhole. They were even willing to allow Sto. Nino to connect with this drainage system, thus sparing the sinkhole from being used as drainage for the domestic wastewater.
The other members of the ad hoc committee were caught in a bind -- the environment committee of Mandaue City, MCWD, SMC, WRC and DENR sit in the Butuanon River Management Board. Formed in 1996, the BRMB aims to rehabilitate and protect the river. In fact, the 30 industries comprising the Butuanon River Industrial Community have already committed in a MOA to treat their wastewater before discharging it to the river. No residential subdivision has ever put up a wasterwater treatment facility. Neither do the cities of Mandaue and Cebu have a sewerage facility.
Both Progeny and Sto. Nino refused to shoulder the entire responsibility of treating the wastewater that go through their properties, adding it is unfair to them. Obviously much of the domestic wastewater and stormwater come from Banilad and Talamban, Cebu City. This includes the run-offs from Ma. Luisa and Dona Rita subdivisions, and University of San Carlos. Sto. Nino sits on the boundary between the two cities, though 2/3 of the subdivision rests in Mandaue.
Here then are some of the solutions that the ad hoc committee came up with:
WIN-WIN SOLUTIONS
To address the water contamination issue
a) Prohibit the draining of untreated wastewater into the sinkhole. Only stormwater should be allowed into the sinkhole.
b) Set up a wastewater treatment facility to treat the wastewater from Sto. Nino Village and other residences and establishments along Banilad road.
c) Cost of operating and maintaining the wastewater treatment facility can be charged to these households and establishments.
To address the flooding and groundwater recharge issues
a) Establish a lagoon that will serve as holding pond for the stormwater
b) Excess storm water can overflow to the sinkhole
c) Excess storm water that will overflow from the lagoon and sinkhole to be channeled thru a 1.8-km drainage system that will drain into the Butuanon River
d) This drainage system will have perforated channels so some amount will be absorbed by the limestone aquifer to replenish the groundwater. At the same time this reduces the volume of water that reaches Butuanon.
To address both water contamination and flooding issues
a) Institute measures to discourage indiscriminate throwing of garbage and other solid wastes that clog and pollute manholes, canals, and the sinkhole
RECOMMENDATIONS
From these win-win solutions, are the tentative recommendations:
1. The Mandaue and Cebu city governments acquire a one hectare plot around the sinkhole to establish the wastewater treatment facility and stormwater lagoon
2. Progeny Development Corp. will donate 600 sq.m. including the sinkhole to be a part of this one hectare plot
3. MCWD to supervise the construction of wastewater treatment facility according to the specifications of DENR; and a 4 meter x 5,000 sq.m. lagoon to hold the stormwater
4. Sto. Nino Village and other subdivisions and establishments that use this drainage system pay maintenance fees to cover the cost of the these wastewater treatment and flood-control facilities
5. Progeny to undertake the cost and civil works in installing the first kilometer of the drainage system up to M.L. Quezon Ave.
6. The Mandaue and Cebu city governments to undertake the installation of the remaining 800-meter drainage to Butuanon River
7. In the meantime that we're awaiting the implementation of (#6), the stormwater in the Progeny drainage will be diverted to the existing city drainage system in MLQ using an MCWD water pump.
The representatives for the city governments of Cebu and Mandaue have reservations about selling the idea to their respective city councils. This is considering that the wastewater treatment facility, lagoon, and 800-meter drainage connection will cost at least P5.4 million.
Not everyone is happy with these "win-win" solutions. The proposed recommendations were arrived at with nagging reservations. Some members of the committee felt that the long-term implications on groundwater resources protection were not satisfactorily addressed. That is, no development and certainly no backfilling should be allowed in the 15-ha. area. Also, that the sinkhole should be sealed to eliminate the threat of contamination.
Councilor Fortuna decided to put these recommendations on hold pending the studies of DENR on the geological characteristics of the area and water analysis of Sto. Nino's drainage system. The geological test will settle the issue if the area is indeed a recharge area or not. The water analysis will establish the degree of pollution entering and exiting Sto. Nino. MCWD would also like the DENR to conduct an infiltration test at the sinkhole to determine its absorption rate and capacity. The WRC had already conducted an infiltration test for Progeny over at their property.
Meanwhile, Progeny is waiting for DENR to lift the cease and desist order. Before it can proceed with its business park project the developer has to comply with the requirements of the Environmental Clearance Certificate. An ECC from DENR is required to obtain a zoning clearance from Mandaue City, and both documents are required to get a building permit from the Mandaue City Engineer's Office.
Progeny is stuck between the devil and the deep blue sea: if it goes ahead in developing its warehouse compound by installing its elevated drainage system to M.L. Quezon Avenue, residents in the flood-prone low-lying areas will oppose their development. To proceed is to incur the ire of the local community.
However, if it opts for the lower drainage system to Butuanon River, how long can the company and its investors afford to wait for government to do its part in establishing the wastewater and flood-control measures? City councils have to vote on it, allocate the required budget, negotiate with different land owners or expropriate land if necessary -- this could take years.
The company has repeatedly warned they will pull out if they are not allowed to develop, and demanded if the Mandaue City government is willing to buy the land at fair market value. The zonal value for the remaining vacant lots is P3,000/sq.m. However, when Progeny offered P6,000/sq.m. for the right-of-way of their drainage, the land owners demanded P15,000 -- and that's only a water-logged converted ricefield.