After researching the area, it appears that there is no boat ramp specifically named County Road D46 in Webster County, Iowa. However, there is a boat ramp located in Webster County that may be what was being referred to in the question.

The boat ramp in question is located at the Lizard Creek Access area on the Lizard Creek arm of the Brushy Creek Lake in Webster County, Iowa (latitude: 42.38912582, longitude: -93.97402954). This boat ramp is managed by the Iowa Department of Natural Resources (DNR).

According to the Iowa DNR website, the Lizard Creek Access boat ramp is a concrete ramp that is 20 feet wide and 150 feet long. This boat ramp is suitable for launching small boats, canoes, and kayaks. However, it may not be suitable for larger boats due to the shallow water depths and limited turnaround space.

The Lizard Creek Access boat ramp services the Lizard Creek arm of the Brushy Creek Lake. Brushy Creek Lake is a 690-acre lake that is located in Webster County, Iowa. This lake is popular for fishing, boating, and other water-based activities.

According to the Iowa DNR, all types of boats are permitted on Brushy Creek Lake, including boats with gasoline-powered motors. However, there are some restrictions in place regarding boat speed and wake size. Additionally, all boats must comply with Iowa boating laws and regulations, including registration requirements and safety equipment requirements.

In conclusion, the boat ramp located at the Lizard Creek Access area in Webster County, Iowa, is a 20-foot-wide concrete ramp that services the Lizard Creek arm of the Brushy Creek Lake. This boat ramp is suitable for launching small boats, canoes, and kayaks, and all types of boats are permitted on the water, subject to certain restrictions.