To assess the appropriate level of hybrid bond usage for Veolia Environnement, we must analyze its financial position as of December 31, 2022.

**1. Financial Context:**
*   **Total Adjusted Capital:** Based on the provided 2023-01-01 figures: Equity (14,866,900,000 EUR) + Noncurrent Financial Liabilities (19,692,100,000 EUR) + Current Financial Liabilities (6,521,400,000 EUR) + Lease Liabilities (1,656,200,000 + 496,500,000 EUR) = ~43.2 billion EUR (approximate debt). With equity of 14.87 billion EUR, total adjusted capital is roughly 58 billion EUR.
*   **Current Hybrid Status:** Veolia already has "Titres Super Subordonnes" (hybrid instruments) of 3,496,300,000 EUR. 
*   **Recent Activity:** Veolia completed the major acquisition of Suez, significantly increasing its "Goodwill" (from 6.2 billion EUR to 11.6 billion EUR) and "Property, Plant and Equipment" (from 8.7 billion EUR to 16.6 billion EUR). This massive expansion reflects a period of intense M&A activity and capital deployment.
*   **Leverage and Rating Pressure:** The significant increase in debt and the integration of Suez create pressure on credit metrics. Maintaining an investment-grade rating is critical for a company of this scale, especially during a period of high interest rates (Swap 10Y moving from ~0% to ~1.9%).

**2. Rationale:**
*   Veolia has transitioned through a major, transformational M&A phase. The integration of Suez requires maintaining financial flexibility to manage the increased leverage and the ongoing capital intensity of the expanded business.
*   The current hybrid portfolio (3.49 billion EUR) is already a substantial component of the capital structure. 
*   Given the "High capex intensity" and the integration of a "large acquisition pipeline" (Suez), there is a strong need to preserve investment-grade credit metrics. 
*   The 11.25% threshold corresponds to situations where investment-grade preservation is strongly dependent on capital structure optimization. An issuance level at 11.25% of total adjusted capital (approx. 6.5 billion EUR total, implying a net increase of ~3 billion EUR) aligns with the annual cap of 3 billion EUR provided in the instructions and supports the company's leverage profile post-acquisition.

**3. Conclusion:**
The company’s capital structure requires support to manage the debt accumulated during the Suez acquisition. An issuance level of 11.25% provides the necessary rating flexibility without hitting the maximum 15% limit, acknowledging that the company already has significant hybrid instruments in place.

<answer>11.25%</answer>