(A) Site design process.
(1) Better site design. Whenever possible, new development projects shall be designed using the better site design techniques of the current version of the state’s storm water manual (available at http://stormwater.pca.state.mn.us/index.php/Better site design). Better site design involves techniques applied early in the design process to preserve natural areas, reduce impervious cover, distribute runoff, and use pervious areas to effectively treat storm water runoff. Site design should address open space protection, impervious cover minimization, and runoff distribution, minimization, and utilization through considerations as follows.
(a) Open space protection and restoration.
1. Conservation of existing natural areas (upland and wetland);
2. Reforestation;
3. Re-establishment of prairies;
4. Restoration of wetlands;
5. Establishment or protection of stream, shoreline, and wetland buffers; and
6. Re-establishment of native vegetation into the landscape.
(b) Reduction of impervious cover.
1. Reduce new impervious surfaces by redeveloping existing sites and reuse of existing roadways, trails, and the like;
2. Minimize street width, parking space size, driveway length, and sidewalk width; and
3. Reduce impervious surface footprint (e.g., two story buildings, parking ramp).
(c) Distribution and minimization of runoff.
1. Utilize vegetated areas for storm water treatment (e.g., parking lot islands, vegetated areas along property boundaries, front and rear yards, building landscaping);
2. Direct impervious surface runoff to vegetated areas or to designed treatment areas (roofs, parking, and driveways drain to pervious areas, not directly to storm sewer or other conveyances);
3. Encourage infiltration and soil storage of runoff through grass channels, soil compost amendment, vegetated swales, rain gardens, and the like; and
4. Plant vegetation that does not require irrigation beyond natural rainfall and runoff from the site.
(d) Runoff utilization. Capture and store runoff for irrigation use in areas where irrigation is necessary.
(2) Storm water criteria. The following general criteria shall be incorporated in site design for storm water runoff to protect surface and ground water and other natural resources by maintaining pre-development hydrological conditions:
(a) Reduce impacts on water;
(b) Protect soils;
(c) Preserve vegetation;
(d) Decrease runoff volume;
(e) Decrease erosion and sedimentation and channel erosion;
(f) Decrease flow frequency, duration, and peak runoff rates;
(g) Increase infiltration (ground water recharge);
(h) Maintain existing flow patterns;
(i) Reduce peak flows; and
(j) Store storm water runoff on-site.
(3) Erosion and sediment control criteria. The following general criteria shall be incorporated in site design for erosion and sediment control:
(a) Minimize disturbance of natural soil cover and vegetation;
(b) Minimize, in area and duration, exposed soil and unstable soil conditions;
(c) Protect receiving water bodies, wetlands, and storm sewer inlets;
(d) Protect adjacent properties from sediment deposition;
(e) Minimize off-site sediment transport on trucks and equipment;
(f) Minimize work in and adjacent to water bodies and wetlands;
(g) Maintain stable slopes;
(h) Avoid steep slopes and the need for high cuts and fills;
(i) Minimize disturbance to the surrounding soils, root systems, and trunks of trees adjacent to site activity that are intended to be left standing; and
(j) Minimize the compaction of site soils.
(B) MIDS calculator. Final site design and choice of permanent storm water volume reduction practices shall be based on outcomes of the MIDS calculator (or other model that shows the performance goal can be met) and shall meet the performance goals in § 53.11. The MIDS calculator is available at http://stormwater.pca.state.mn.us/index.php/Calculator.
(Ord. 2016-06, passed 5-23-2016)