Regardless of your project location in the United States, we are all governed by federal regulations controlling the transmission of storm water from our project or facility site. That movement of storm water, away from your site, is done via a storm sewer system. There are two ways to deal with storm water regulations:
1 - The most economical way to deal with storm water regulations, is to find and retro-fit an existing building. (We seem to have no shortage of "see-through" buildings.) If you find a suitable building, do not add to the area of the existing building or parking lot. Verify the existing zoning compatibility and parking for your use. If there is a conflict or potential conflict with zoning, examine the viability of a Conditional Use Permit, Zoning Modification or even a Zone Change. Proceed with your design approvals and construction.
2 - The other option is storm water compliance which for new construction, will always trigger federal requirements (molded into California language), requiring an engineered method of either holding water that falls from the heavens onto your property, for reuse (i.e. to irrigate your landscaping) or to be re-infused (percolated) into the ecosystem. In the case of additions to buildings or parking lots totaling over 5,000 square feet of impervious surfaces, similar requirements apply on a prorated basis of building value. However, once the value of the proposed improvement reaches 50% of the value of the existing building, full storm water controls are required.
Why have these storm water requirements been mandated?
Storm sewer systems across the country are above capacity. The addition of roofs, parking lots and other imperious surfaces compound the problem of flooding and the spread of pollutants to waterways and the oceans. The Environmental Protection Agency has taken measures to slow increased runoff from new sources by imposing storm water controls on new construction. Each state in these United States, has been issued a State Stormwater Permit. It is up to each state to administer storm water controls for the transmission of storm water in the public storm sewer (in federal EPA speak, Municipal Separate Storm Sewer Systems (MS4s)) within their jurisdiction.
California, in turn, has issued a Storm Water Permit to each of it's counties and/or specialized municipal watershed areas. The central portion of Los Angeles County and Ventura County were issued their updated MS4 permits last fall (2013). Northeast LA, Kern County, San Bernadino and Riverside Counties were issued their updated permits in January, 2014. The general requirements are all the same.
What questions you SHOULD be asking:
What is Stormwater retention?
A: Water falling from the sky onto your site will be yours to keep. Remember, transmission of storm water has experienced significant increased regulation. Full compliance for your site is such that you cannot produce more storm water runoff than would come from no more than 5% of your site area being covered by roof or pavement. Small projects, that is, projects that are less than 50% of the value of any existing facility on your site, can be permitted to have a reduction in the required retention. Over 50% in construction value will require full site retention.
When will my site trigger compliance with new storm water requirements?
A: Any construction activity is subject to a storm water permit, at least in a minimal way, of protecting the surrounding area from construction debris and runoff. This is a normal part of construction and is just good housekeeping. However, If you are considering construction activity that will add impervious surface (parking lot or roof) of 5,000 square feet or more, you will become subject to a storm water retention.
So, what am I supposed to do with all this storm water?
A: If your site has excess land available, you may be able to direct the water there. Without the luxury of excess land, you will need to store the water on site, usually in an under-parking lot cistern, built up using modular components such as those offered by:
The concept with these water storage solutions, is that you build into your project a system that will either store the water for later use; i.e. for landscape irrigation, as in the case of a tank system; or percolate the water back into the ground. Soil conditions can vary, so the percolation option will depend on local conditions. The cost for any of these water storage systems can easily be overlooked, and most certainly overlooked is the engineering cost involved. Knowing in advance whether or not your project is a candidate for storm water retention, can make or break a deal.
In today's market, the viable option is to look at existing buildings. Existing buildings do not carry the liability of major storm water retention (unless you cross the threshold of 50% valuation improvements and an addition over 5,000 s.f.). Investors note: For the near term, existing buildings have the upper hand on the market for this reason. The emphasis is on re-purposing existing buildings, avoiding storm water issues all together. If considering an existing building, be sure to check out my comments on Zoning and Parking.
- Patrick McIlhenney, AIA