Final answer:
The quantity of sand deposited on the beach in 2006 is not provided. Therefore, the question about how often the beach needs replenishing cannot be answered.
Step-by-step explanation:
The information provided does not specify the exact amount of sand deposited on the beach in 2006, making it challenging to determine the quantity added during that specific year. However, it does highlight that by the end of 2012, a substantial 137,000 cubic meters of sand were used to cover a contaminated area of 30,000 square meters. This suggests a significant replenishment effort during that timeframe.
The frequency at which a beach needs replenishing depends on various factors, including natural erosion, weather conditions, and human activities. Without additional details on the annual rates of sand loss or erosion, it is not possible to accurately calculate how often the beach requires replenishment.
To assess the replenishment interval, one would need information on the rate of sand loss per year, which could be influenced by factors such as storms, tides, and human impact. If the rate of erosion is known, it would be possible to estimate how frequently the beach needs replenishing to maintain its size and ecological balance.
In summary, while the data confirms a substantial replenishment effort by the end of 2012, the lack of specific information on the sand deposition in 2006 and annual erosion rates precludes a precise determination of how often the beach requires replenishing. Additional details on the dynamics of sand movement and erosion over time would be necessary to make a more accurate assessment.