Queenston Manor Apartments Part II LID Hydraulic Impact Analysis

Transcription

1 Part II LID Hydraulic Impact Analysis Jerry P. Preston, P.E., CFM EHRA, Inc.

2 South of FM 529 and north of W. Little York Road Blvd is the west boundary Langham Creek is the east boundary Rice University February 26, 2013

3 Goal of modern conventional drainage is to remove runoff quickly, efficiently and completely Conventional drainage achieves this goal, but requires large infrastructure expense LID DRAINAGE REQUIRES A CHANGE OF PERSPECTIVE EHRA, Inc.

4 LID DRAINAGE REQUIRES A CHANGE OF PERSPECTIVE LID drainage concepts and principals: decentralize conveyance and detention treat runoff at its source distributed micro-scale practices - spread it out mimic natural drainage processes time of concentration, infiltration, volume and flow time-tested technology, different application like conventional methods, drainage is still designed to avoid flood damages and support mobility slower does not mean less efficient

5 HCFCD CHANNEL Raingardens Underground storage Pervious pavement (parking) NORTH Vegetated swales

6 HYDROLOGY Analyzed 2-year (6-hour), 10-year (24- hour) and 100-year (24-hour) events Rational Method Peak Flow for each DA Hydrographs for each DA using Clark s UH Method in HEC-HMS Used actual Tc and calibrated Storage Coefficient R to match Rational Method Peak Flow

7 HYDROLOGY 7.2-ac site divided into 41 inlet drainage areas: Pervious pavement sections Vegetated swales Raingardens

8 HYDRAULICS Dynamic routing using EPA-SWMM software System of nodes and links Nodes: Raingardens (storage area) Pervious Pavement (storage area) Manholes/Junctions Links: Underground pipe (6-24 ) Overflow Inlets

9 HYDRAULICS 3 outfalls into adjacent HCFCD channel 54 nodes 51 links

10 RAIN GARDEN = DETENTION STORAGE

11 RAIN TANKS aka DETENTION STORAGE

12 VOID VOLUME = DETENTION STORAGE

13 ENGINEERED SOIL FILTER FOR SWQ

14 ENGINEERED SOIL FILTER with UNDERDRAIN and OVERFLOW INLET

15 2-year System Hydrographs

16 10-year System Hydrographs

17 100-year System Hydrographs

18 EVALUATING RESULTS Pre- Development Post- Development Peak 100-yr Runoff Rate 11.7 cfs 7.9 cfs Peak 10-yr Runoff Rate 8.5 cfs 6.9 cfs Peak 2-yr Runoff Rate 6.0 cfs 5.9 cfs Time of Concentration 16.7 min min. Total detention storage provided (sum of storage utilized in permeable paver subgrade, raingardens and vegetated swales) = 2.7 ac-ft Total detention storage rate = 0.38 ac-ft/ac (Typical detention storage rate = 0.55 ac-ft/ac)

19 CONCLUSION Distributed micro-scale features contribute to more efficient detention storage, no adverse impact to receiving stream Engineered soil filter provides dramatically better SWQ benefits compared to conventional trash rack Much greater engineering/analysis effort required than conventional route Net result: more efficient land plan + attractive product = happy client!

20 Thank You Questions? Edminster Hinshaw Russ & Associates, Inc. Civil Engineering Surveying Land Planning Platting Landscape Architecture Hydrology & Hydraulics Construction Phase Services Public Works Bridges & Structures Transportation Planning Rice University February 26, 2013