Quantity of stormwater is typically the more difficult measurement for project teams to reduce. Detention basins can help reduce peak flow rate, but they may not reduce overall stormwater quantity. This is a common municipal requirement, and you may need to take additional measures to meet the credit requirements.
Some jurisdictions may have stormwater standards that are similar to the LEED requirements. For example, Portland, Oregon's Title 17, Public Improvements, Chapter 17, 17.38.030 Section C, states that the quantity and flow rate of stormwater leaving the site after development shall be equal to or less than the quantity and flow rate of stormwater leaving the site before development, as much as is practicable.
Research historical climate records to understand the frequency, intensity, and duration of the design storm event. A longer record of daily rainfall events (rather than monthly rainfall averages) will result in more accurate sizing of components like cisterns.
Most credit compliance problems are due to stormwater volume reduction, in part because many municipalities are more interested in runoff rate and do not require volume calculations. A civil engineer must run calculations for pre- and post-development runoff rate and quantity, for the one- and two-year, 24-hour design storm. Most jurisdictions don’t require calculations for these specific storm designs.
Using site space for stormwater management is often a must. Architects and owners may see stormwater best management practices (BMPs) as wasting valuable land—a mentality that can make this credit difficult. It may help to stress that stormwater BMPs can act as aesthetic features that enhance the quality of the site and add value to the project. Creative, integrated approaches can even reduce space-hogging, unattractive strategies like detention ponds while adding amenities with multiple benefits, like green roofs.
The easiest way to achieve credit compliance is by decreasing impervious area. You can do this by reducing the building footprint and hardscape area, and establishing rain gardens or other bioretention areas.
Educate staff and occupants on daylight-related and glare-control technologies. Some daylighting controls such as shades or blinds may require occupant operation, and without instruction, may not be used properly, resulting in the building not operating as designed.
Measuring daylight levels can be a time-consuming process in large buildings. Measurements are taken on a 10-foot by 10-foot grid, with four measurement points for each 10 ft2 section. Taking and recording each measurement takes about 30 seconds—not including setting up the grid—for a total of about two minutes per grid section.
A hybrid compliance path may be the best solution for some projects. For example, if most of the regularly occupied spaces pass the calculation criteria in the prescriptive path, and a portion of the spaces fall short very narrowly or use strategies like lightshelves not accounted for by the prescriptive path, measurement of those spaces after finishes are complete could demonstrate that they are sufficiently daylit after finishes are complete.
